BIOLOGY

What is biology?

The word biology is derived from the greek words /bios/ meaning /life/ and /logos/ meaning /study/ and is defined as the science of life and living organisms. An organism is a living entity consisting of one cell e.g. bacteria, or several cells e.g. animals, plants and fungi. Aspects of biological science range from the study of molecular mechanisms in cells, to the classification and behaviour of organisms, how species evolve and interaction between ecosystems.

The study of biology can be divided into different disciplines –
• Ethology
• Evolutionary Biology
• Physiology
• Genetics
• Molecular Biology
• Morphology
• Systematics
• Ecology

Biology often overlaps with other sciences; for example, biochemistry and toxicology with biology, chemistry, and medicine; biophysics with biology and physics; stratigraphy with biology and geography; astrobiology with biology and astronomy. Social sciences such as geography, philosophy, psychology and sociology can also interact with biology, for example, in administration of biological resources, developmental biology, biogeography, evolutionary psychology and ethics.

Genetics

Genetics is the study of heredity. If you understand genetics you will be able to work out why you look like each of your parents and your siblings (brothers and sisters) but are not exactly like any one of them: unless you have an identical twin.
Don't be worried in the exam if you are given an example which you have not studied: if you understand the principles you will probably find GCSE question on genetics quite easy.
Don't you just hate it when you are lying in your pram gurgling away and all your dad's family come up and say "Ooooh doesn't he look just like his dad?" and then all your mum's family come and say "Oooh doesn't she look just like her mum?". None of them studied genetics!

Index
DNA
Genes and Alleles
Chromosomes
Inheritance of Sex
Blue and Brown eyes (other colours as well)
PKU
Albinism
Haemophilia
Sickle Cell
How you inherit your Blood Group

Glossary

All living things inherit their characteristics in very much the same way. What you learn here is true for all animals, green plants and fungi. There a some differences in the mechanisms in prokaryotes even though they use DNA as we do. This page is just about inheritance in Eukaryotes, i.e. those things with proper nuclei. (animals, green plants and fungi.)

DNA

DNA stand for Deoxyribo Nucleic Acid; you don't need to remember what DNA stands for in your GCSE exam, but should should know that DNA is a very special chemical which carries the hereditary information in almost all living things. (Some viruses use RNA instead of DNA.) DNA is special because it carries the genetic code which determines how cells make proteins AND it can be replicated exactly.
So when a cell divides, it begins by duplicating all its DNA. This DNA is then divided between the two daughter cells produced in mitosis. We all started our lives inside our mums as a single fertilised egg or zygote. Within a few hours of conception we started to divide and divide again and again into millions of cells. Because these divisions were genetically exact, each one of us consists of billions of genetically identical cells. Siblings (brothers and sisters) are normally created from totally different eggs and sperms and so whilst we are similar to our siblings we are not identical to them. Very occasionally a single fertilised egg separates into two separate cells which each become a developing baby. In this case the two babies will be identical twins: you will discover as you read on why identical twins MUST be the same sex (two girls or two boys) and ordinary twins could be the same sex or different sexes.

Genes and Alleles

The nuclei in our cells are not test tubes containing lots of chemicals all mixed together. In fact there is a lot of DNA inside every nucleus but it is all carefully organised. A human cell contains millions of bits of DNA, each bit is a piece of information which is used to control how the cell works and ultimately what we look like. My hair is brown (well it is supposed to be brown) because that is what the information in my genes make it (this is my genotype). If you saw me you would see that it is now going grey, that is because of all the stress that I have as a teacher and because I am getting older; this is not to do with my genes but is caused by my environment (what you see is my phenotype). For every characteristic a cell contains two bits of DNA or genes. These two genes may be the same as each other (homozygous) or different to each other (heterozygous).
There are three possible combinations that you might inherit: two dominant alleles, two recessive alleles, or one dominant and one recessive allele. e.g. I know that I have two different alleles for eye colour. I have brown eyes because I inherited a brown eye allele from my father who also had brown eyes, but I have also inherited a blue eye allele from my mother who has blue eyes. Because the brown eye allele is dominant my eyes are brown.

Chromosomes

Human cells normally contain 46 chromosomes. A chromosome is a thread of protein with many genes attached to it. I prefer to think of these chromosomes as 23 pairs rather than as 46 separate ones; this is because each one of us inherits 23 chromosomes from each parent. When we make gametes (sperms and eggs) a different kind of cell division occurs. In the testis and ovary cells divide by another kind of cell division called meiosis in which the number of chromosomes is reduced from 46 to 23. When a sperm fertilises an egg, there will be 23 pairs of chromosomes again. Of these 23 pairs of chromosomes, 22 pairs control quite ordinary features like eye colour and hair colour. One pair of chromosomes controls sex i.e. which one you will be. These are the X and Y chromosomes.

Inheritance of Sex

Girls/women always carry two X chromosomes in every cell of their bodies. When they make eggs by meiosis the number of chromosomes is cut in half; so eggs only contain one X chromosome.
Boys/men only have one X chromosome, but they also have a Y chromosome in every cell. When they make sperms, some of the sperms carry an X chromosome and some carry the Y chromosome instead. XX make you female, XY makes you male.
The X chromosome carries some genes which have very little if anything to do with the inheritance of sex. These characteristics, e.g. haemophilia, colour blindness, are sex linked: in other words the inheritance of these genes is linked to the inheritance of sex because they are carried on the sex chromosomes. The Y chromosome is very small and carries very few genes. The genes for sex linked characteristics like haemophilia have an interesting pattern of inheritance. Women have two genes for normal blood clotting whereas men only have one gene for blood clotting on the X chromosome (the Y chromosome does not have this gene.)

Blue and Brown Eyes

The allele for brown eyes is dominant, and the allele for blue eyes is recessive. I use the symbol B for the brown eye allele and b for the blue allele. There are three possibilities: BB, Bb and bb. These are the three possible genotypes. If you inherit either BB or Bb then you will have brown eyes. If you inherit bb you will have blue eyes. (I am counting brown, black and hazel eyes as being brown and blue, grey and green as being blue: other genes determine what shade of blue or brown your eyes are.) The two possible phenotypes are blue eyes and brown eyes.

PKU

This is a genetic disease in which the liver is unable to remove the chemical phenyl ketone which ends up being carried around the body in the blood and excreted in the urine: it is caused by a recessive gene. Phenyl ketone is a solvent and it causes damage to nerve cells. (to be updated ASAP.) PKU is passed on from generation to generation by the same simple mechanism as eye colour. Approximately 1 person in 80 carries the mutant (defective or changed) gene for PKU. The chances of two people both carrying this mutant gene are 1 in 6400; and the chance of them having a baby with PKU is about 1 in 25600 so there is no need to worry about it unless there is a history of this disease in your family.

Albinism

Albinism is caused by a mutant gene carried by about 1 person in 1000. The chance of two people both carrying the gene is about 1 in a million; and of a baby being born with two mutant genes is 1 in 4 million. I have seen 2 albinos in London. Albino means white. Someone who inherit two recessive albino genes cannot make the black pigment called melanin. Most of us make melanin in our skin, hair and at the back of our eyes. (to be updated ASAP.) Again, the pattern of inheritance is a simple one just as for PKU and eye colour.

Haemophilia

The inheritance of this genetic disease is a bit more complicated because it is sex linked. Women normally have two genes for blood clotting, one on each X chromosome. Men only have one blood clotting gene because they only have one X chromosome. This gene is not present on a Y chromosome. Some women carry a defective gene for haemophilia. These women are called carriers. Their daughters may be normal or may be carriers. Their sons are either normal or actually have the disease. A haemophiliac male has problems when blood vessels are damaged because his blood will not clot properly. He can pass the gene on to his daughters who will be carriers. ALL his daughters will be carriers because the defective gene is on the X chromosome. There is nothing wrong with his Y chromosomes, so his sons will all be perfectly normal.
Some of Queen Victoria's descendants inherited this gene from her. She must have been a carrier. If you read about the Russian Revolution, you will find out about Tsar Nicholas and his family getting murdered by the Bolsheviks. The Tsar's son Alexis (the Tsarevitch) did not die of haemophilia! He suffered terribly from haemophilia and his mother (the Tsarina) asked the monk Rasputin to help cure her son. However anyone would die if the were filled up with bullet holes. The story of The Tsar and his family is a very interesting one. Ask your history teacher who inherited the Romanov family fortune.

Sickle Cell

The inheritance of this genetic disease is a bit more interesting because it can be an advantage to have the gene as well as being a disadvantage. In this case there are three possible phenotypes instead of two. Most people produce normal Haemoglobin (this is the protein found in red blood cells which carries oxygen around the body). Sickle cell Haemoglobin is very slightly different. Sickle cell Haemoglobin works just as well as ordinary Haemoglobin unless the Oxygen level in the blood goes down to zero; this happens when someone is running in a race and builds up an oxygen debt. When you have an Oxygen debt your muscles start to make lactic acid. Sickle cell red blood cells collapse when they have no Oxygen; this can result in death!!!

So ordinary people have two ordinary Haemoglobin genes HH. Some people have two sickle cell genes SS; they have the full sickle cell anaemia. Neither the H nor the S allele is dominant; so biologists just have to give it a special name: they call this co-dominance. People who inherit both alleles, HS, have sickle cell trait. Their red blood cells contain both kinds of Haemoglobin.

Obviously if you have a gene which might kill you, you would consider it to be a very big disadvantage! However, if you live in an area of the world where malaria is a common disease there is an advantage in having the sickle cell gene. When the malaria parasite gets into red blood cells they quickly use up all the Oxygen in them; this results in the red blood cells collapsing; this happens before the malaria parasite can reproduce.

Why do people make such a fuss about HIV and AIDS? It is malaria which kills the most people in the world every year. Having sickle cell can be a very big advantage; you can let the mosquitoes bite you without getting malaria. Providing that you do not get overstressed and build up an Oxygen debt, you will live happily ever after.

What Are the Signs and Symptoms of Sickle Cell Anemia?

The signs and symptoms of sickle cell anemia are different in each person. Some people have mild symptoms. Others have very severe symptoms and are often hospitalized for treatment. Although sickle cell anemia is present at birth, many infants don’t show any signs until after 4 months of age.

The most common signs and symptoms are linked to anemia and pain. Other signs and symptoms are linked to some of the complications of the condition.

Anemia

The general signs and symptoms of anemia are fatigue (tiredness), pale skin and nail beds, jaundice (yellowing of the skin and eyes), and shortness of breath.

Pain (Sickle Cell Crisis)

Sudden episodes of pain throughout the body are a common symptom of sickle cell anemia and are often referred to as “sickle cell crises.”

A sickle cell crisis occurs when the red blood cells sickle (become “C” shaped) and stick together in clumps. The clumps block the flow of blood through the small blood vessels (capillaries) in the limbs and organs.

Sickle crises can cause acute or chronic pain. Acute pain is the most common type. This is sudden pain that can range from mild to very severe. The pain usually lasts from hours to a few days. Chronic pain usually lasts for weeks to months. Chronic pain can be hard to bear and mentally draining. This pain may severely limit daily activities.

Almost all people with sickle cell anemia have painful crises at some point in their lives. Some have a crisis less than once a year. Others may have 15 or more crises in a year.
Many factors can contribute to a sickle cell crisis. Often, more than one factor is involved and the exact cause can’t be identified. Factors that occur in your body and aren’t under your control can cause a sickle cell crisis, such as an infection.

Factors that you can control also can affect whether you have a sickle cell crisis. For example, dehydration (when your body doesn’t have enough fluid) can increase your chances of having a sickle cell crisis. Drinking plenty of fluids so your body is hydrated can often help decrease the chance of a crisis.

The most common sites affected by sickle cell crises are the bones, lungs, abdomen, and joints. The blocked blood flow can cause pain and organ damage.

Complications of Sickle Cell Anemia

Complications of sickle cell anemia come from the effects of sickle cell crises on different parts of the body.

Hand-Foot Syndrome

When sickle cells block the small blood vessels in the hands or feet, pain and swelling along with fever can occur. One or both hands and/or feet may be affected at the same time. Pain may be felt in the many bones of the hands and feet. Swelling usually occurs on the back of the hands and feet and moves into the fingers and toes. This may be the first sign of sickle cell anemia in infants.

Splenic (Sequestration) Crisis

The spleen is an organ in the abdomen that filters out abnormal red blood cells and helps fight infection. Sometimes, the spleen traps many cells that should be in the bloodstream and it grows large. This causes anemia. Blood transfusions may be needed until the body can make more cells and recover. If the spleen becomes too clogged with sickle cells, it can’t work normally. It begins to shrink and stop working.

Infections

Both children and adults with sickle cell anemia have a hard time fighting infections. Sickle cell anemia can damage the spleen.
Infants and young children with a damaged spleen are more likely to get infections that can kill them within hours or days. Pneumonia is the most common cause of death in young children who have sickle cell anemia. Meningitis, influenza, and hepatitis are other infections that are common in people with sickle cell anemia.

Acute Chest Syndrome

Acute chest syndrome is a life-threatening condition linked to sickle cell anemia. It's similar to pneumonia and is caused by an infection or by sickle cells trapped in the lungs. People with this condition usually have chest pain, fever, and an abnormal chest x ray. Over time, lung damage may lead to pulmonary arterial hypertension (see below).

Delayed Growth and Puberty in Children

Children with sickle cell anemia often grow more slowly and reach puberty later than other children. A shortage of red blood cells (anemia) causes the slow growth rate. Adults with sickle cell anemia often are slender or small in size.

Stroke

Sickle-shaped red blood cells may stick to the walls of the tiny blood vessels in the brain. This can cause a stroke. This type of stroke occurs mainly in children. The stroke can cause learning disabilities or more severe problems.

Eye Problems

The retina, a thin layer of tissue at the back of the eye, takes the images you see and sends them to your brain. When the retina doesn’t get enough blood, it can weaken. A weak retina can cause serious problems, including blindness.

Priapism

Males with sickle cell anemia may have painful and unwanted erections called priapism (PRI-a-pizm). This happens because the sickle cells stop blood flow out of an erect penis. Over time, priapism can damage the penis and lead to impotence.

Gallstones

When red blood cells die, they release their hemoglobin, which the body breaks down into a compound called bilirubin. When there is too much bilirubin in the body, stones can form in the gallbladder.

Gallstones can cause steady pain that lasts for 30 minutes or more in the upper right side of the belly, under the right shoulder, or between the shoulder blades. The pain may happen after eating fatty meals. People with gallstones may have nausea, vomiting, fever, sweating, chills, clay-colored stool, or jaundice (yellowish color of the skin or whites of the eyes).

Ulcers on the Legs

Sickle cell ulcers (sores) usually begin as small, raised, crusted sores on the lower third of the leg. Leg sores occur more often in males than in females and usually appear between the ages of 10 and 50. The cause of leg ulcers is not clear. The number of ulcers can vary from one to many. Some heal rapidly, but others persist for years or come back after healing.

Pulmonary Arterial Hypertension (High Blood Pressure)

Damage to the small blood vessels in the lungs makes it hard for the heart to pump blood through the lungs. This causes blood pressure in the lungs to increase. This condition is called pulmonary arterial hypertension. Excessive shortness of breath is an important symptom linked to this problem.

Multiple Organ Failure

Multiple organ failure is rare, but serious. It happens when a person has a sickle cell crisis that causes two out of three major organs (lungs, liver, or kidney) to fail. Symptoms linked to this complication are a fever and changes in mental status such as sudden tiredness and loss of interest in your surroundings.

How Is Sickle Cell Anemia Diagnosed?

Early diagnosis of sickle cell anemia is very important so that children who have the condition can get proper treatment.
In the United States, 44 States, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands now test all newborns for sickle cell anemia. In the other six States, you can request a sickle cell test.
The test uses blood from the same blood samples used for other routine newborn screening tests. It can show whether the newborn infant has sickle cell anemia or sickle cell trait. If the first test shows some sickle hemoglobin, a second blood test is done to confirm the diagnosis.
The second blood test looks at how hemoglobin moves in an electric field, a process called electrophoresis (ee-LEK-tro-for-EE-sis). Sickle hemoglobin moves differently than normal hemoglobin. Electrophoresis is usually used to diagnose older children and adults.
It’s also possible to identify sickle cell anemia before birth. This is done using a sample of amniotic fluid or tissue taken from the placenta. (Amniotic fluid is the fluid in the sac surrounding a growing embryo. The placenta is the organ that attaches the umbilical cord to the mother’s womb.) This test can be done as early as the first few months of pregnancy. It identifies the sickle gene, rather than the hemoglobin it makes.

How Is Sickle Cell Anemia Treated?

Effective treatments are available to help relieve the symptoms and complications of sickle cell anemia, but in most cases there’s no cure. Some researchers believe that bone marrow transplants may offer a cure in a small number of cases. Researchers are looking for new treatments for sickle cell anemia, including gene therapy and safer and more effective bone marrow transplants.
People who have sickle cell anemia need regular medical care. Some doctors and clinics specialize in treating people with the condition. Doctors specializing in sickle cell anemia are often hematologists (doctors who treat people with blood disorders)—or pediatric hematologists (if they also treat children).

Goals of Treatment

The goals of treating sickle cell anemia are to relieve pain; prevent infections, eye damage, and strokes; and control complications if they occur. The treatments include medicine, blood transfusions, and specific treatment for complications.

Treating Pain

Mild painful crises can be managed with treatments such as over-the-counter medicine and heating pads. However, severe pain may need to be treated in a hospital. Painful crises are the leading cause of emergency room visits and hospitalizations of people with sickle cell anemia.
The usual treatments for acute (short-term) pain crises are pain-killing medicines and fluids, given either by mouth or through a vein, to prevent dehydration (a condition in which your body doesn’t have enough fluids). The pain-killing medicines most often used are acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), and narcotics such as meperidine, morphine, oxycodone, and others.
The treatment of patients who have mild-to-moderate pain usually begins with NSAIDs or acetaminophen. If pain continues, a narcotic may be added. Moderate-to-severe pain is often treated with narcotics. The narcotic may be used alone or together with NSAIDs or acetaminophen. Narcotic abuse and addiction are pain management issues that must be considered in any pain control plan.
A medicine called hydroxyurea may be given to adults and older adolescents with severe sickle cell anemia to reduce their number of painful crises. This medicine is used only to prevent these crises, not to treat them when they occur. Given daily, hydroxyurea can reduce the frequency of painful crises and of acute chest syndrome. People taking the medicine also may need fewer blood transfusions.
People taking hydroxyurea must be watched carefully because the medicine can cause serious side effects, including an increased risk of dangerous infections. Some evidence suggests that long-term use of hydroxyurea can cause tumors or leukemia. Because of these risks, the medicine is usually only used in adults and older teenagers with severe sickle cell anemia. Although hydroxyurea is being tested in infants and children at this time, it won’t be approved for use in children until its long-term effects can be more closely studied.

Preventing Infections

Infection is a major complication of sickle cell anemia. In fact, pneumonia is the leading cause of death in children with the condition. Other infections common in people with sickle cell anemia include meningitis, influenza, and hepatitis. If a child with sickle cell anemia shows early signs of an infection, such as fever, seek treatment right away.
To prevent infections in babies and young children, treatments include:
Daily doses of penicillin. Treatment may begin as early as 2 months of age and continue until the child is at least 5 years old.
Vaccinations for pneumonia, meningitis, influenza, and hepatitis.
A yearly flu shot.
Adults who have sickle cell anemia also should have flu shots every year and be vaccinated for pneumonia.

Preventing Eye Damage

Sickle cell anemia can damage the blood vessels in the eyes. Parents should ask their child’s doctor about regular checkups with an eye doctor who specializes in diseases of the retina. The retina is a thin layer of tissue inside the back of the eye. Adults with sickle cell anemia also should have regular checkups with an eye doctor.

Preventing Strokes

Stroke prevention and treatment is now possible for children and adults who have sickle cell anemia. Starting at age 2, children with sickle cell anemia often receive regular ultrasound scans of the head (this is called transcranial Doppler ultrasound). These scans are used to monitor blood flow in the brain.
The scans allow doctors to find out which children are at high risk for a stroke and treat them with regular blood transfusions. Routine blood transfusions have been found to greatly reduce the number of strokes in children.

Blood Transfusions

Blood transfusions are used to treat worsening anemia and sickle cell complications. A sudden worsening of anemia due to an infection or enlargement of the spleen is a common reason for a blood transfusion. Some, but not all, patients need transfusions to prevent life-threatening events such as stroke or pneumonia.
Regular blood transfusions do have side effects, and patients must be carefully watched. Side effects can include a dangerous buildup of iron in the blood (which must be treated) as well as an increased risk of infection from the transfused blood.

Treating Other Complications

Acute chest syndrome is a severe and life-threatening complication in children and adults who have sickle cell anemia. Treatment usually requires hospitalization and may include oxygen, blood transfusions, antibiotics, pain medicine, and monitoring the body’s fluids.
Leg ulcers can be painful, and patients may be given strong pain medicines. Ulcers can be treated with cleansing solutions and medicated creams or ointments. Skin grafts may be needed if the condition continues. Bed rest and keeping the legs raised to reduce swelling are helpful, although not always possible.
Gallbladder surgery may be needed if the presence of gallstones leads to gallbladder disease.
Priapism can be treated with fluids or surgery.
Regular Health Care for Children
Children with sickle cell anemia should get regular health care, just like children without the condition. They need to have their growth checked and to get the usual shots that all children receive.
It’s recommended that before age 2, children with sickle cell anemia see the doctor often (sometimes every 2 or 3 months). After age 2, children may need to see the doctor less often, but usually at least every 6 months. These visits are a time for parents to talk with their child’s doctor and ask questions about the child’s care. Parents should ask about eye checkups and the need for an ultrasound scan of the brain.
Until age 5, daily penicillin is given to most children who have sickle cell anemia. Many patients are prescribed a vitamin called folic acid (folate) to help prevent some of the complications of sickle cell anemia.

New Treatments

Today, research on sickle cell anemia is looking at bone marrow transplants, gene therapy, and new medicines. The hope is that these studies will provide better treatments for sickle cell anemia. Researchers also are looking for a way to predict the severity of the condition.

Bone Marrow Transplant

Bone marrow transplant can be a very effective treatment for sickle cell anemia, but because of its risks, only some patients can or should have this procedure.
The bone marrow transplant procedure is risky and could result in serious side effects and even death. It’s usually used only for younger patients with severe sickle cell anemia, but the decision is made on a case-by-case basis.
Bone marrow used for a transplant must come from a closely matched donor, usually a close family member, who doesn’t have sickle cell anemia.

Gene Therapy

Gene therapy is being studied as a possible treatment for sickle cell anemia. Researchers are looking to see whether a normal gene can be planted in the bone marrow of a person with sickle cell anemia, and thus cause the body to produce normal red blood cells. Researchers also are studying the possibility of treatment to “turn off” the sickle cell gene or “turn on” a gene that makes red blood cells behave normally.

New Medicines

New medicines being studied are:

Butyric acid. This is a food additive that may increase normal hemoglobin in the blood.
Clotrimazole. This is used now to treat fungus infections. This medicine helps prevent the loss of water from a red blood cell and can keep the cell from turning into a sickle cell.
Nitric oxide. This may make sickle cells less sticky and keep blood vessels open. People with sickle cell anemia have low levels of nitric acid in their blood.

How Can Sickle Cell Anemia Be Prevented?

Sickle cell anemia is an inherited condition. Children who inherit the genes for sickle cell anemia can’t prevent developing the condition, although they can take steps to reduce complications.
People who are in groups that are at high risk for sickle cell anemia and who are planning to have children may want to consider genetic counseling beforehand. A counselor can help you understand your risk of having a child with the condition and help explain the choices that are open to you. You can get information about genetic counseling from health departments, neighborhood health centers, medical centers, and clinics that care for people with sickle cell anemia.
A procedure called pre-implantation genetic diagnosis can improve the chance that two people with sickle cell trait will have a child with normal hemoglobin. Eggs from the mother and sperm from the father are mixed together in a laboratory dish. The eggs that become fertilized are checked for sickle cell anemia. Fertilized eggs that don’t have sickle cell genes are then implanted in the mother’s womb. This is a complex procedure done only in a few places, and it doesn’t always work.

Living With Sickle Cell Anemia

With good health care, many people with sickle cell anemia can live productive lives, have reasonably good health much of the time, and live longer today than in the past. Many people who have sickle cell anemia now live into their forties or fifties, or longer.

If you have sickle cell anemia, it’s important to take good care of yourself, do what you can to prevent sickle cell crises, and get regular medical care. Find out all you can about your condition and learn what signs to watch out for.

To take care of your health, you should maintain healthy lifestyle habits. These include:
Eating healthy. Your doctor also may recommend a vitamin (folic acid) to take every day to help your body make new red blood cells.

Drinking at least 8 glasses of water every day, especially in warm weather.

Exercising regularly, but not to the point that you become very tired. Drink lots of fluids when you exercise. Talk with your doctor about how much exercise is right for you.

Getting enough sleep and rest. Tell your doctor if you think you may have a sleep problem such as snoring or sleep apnea (a condition in which you stop breathing for short periods during sleep).

Limiting the amount of alcohol you drink.

Quitting smoking.

Along with healthy lifestyle habits, there are some things you can do to help prevent a sickle cell crisis:

Contact your doctor if you have any signs of an infection, such as a fever or trouble breathing.

Get treated right away. You may want to avoid decongestants, such as pseudoephedrine, that can constrict blood vessels.

Avoid extremes of heat and cold. Wear warm clothes outside in cold weather and inside of air-conditioned rooms. Don’t swim in cold water or climb at high altitudes without extra oxygen.

Reduce the stress in your life. Talk to your doctor if you’re depressed or having problems on the job or with your family. Support from family and friends as well as a support group can help you cope with daily life. If possible, don’t seek jobs that will require strenuous physical labor, expose you to extremes of heat and cold, or involve long work hours.

Don’t travel in airplanes where the cabin isn’t pressurized (that is, no extra oxygen is pumped into the cabin). If you must travel in such an airplane, talk to your doctor about how to protect yourself.

Regular medical checkups and treatment are important.

Checkups may include tests for possible kidney, lung, and liver diseases as well as any side effects from medicines you take. See a sickle cell anemia expert regularly.

Learn the symptoms of a stroke and report them to your doctor promptly. Symptoms of stroke can include a lasting headache, weakness on one side of the body, limping, or a sudden change in speech, vision, or hearing. A change in behavior also can be a symptom of a stroke.

Get a flu shot and other vaccinations to prevent infections.

See your dentist regularly to prevent infections and loss of teeth.

See an eye doctor regularly to check for damage to your eyes.

Get treatment and control any other medical conditions you might have, such as diabetes.

Talk with your doctor if you’re pregnant or planning to become pregnant. You will need special prenatal care. Sickle cell anemia can become more severe during pregnancy, with more painful crises. Women with sickle cell anemia also are at an increased risk for an early birth or a low-birth-weight baby. You can have a healthy pregnancy with early prenatal care and frequent checkups.

Coping With Pain

Pain is different for each person. Pain that one person can live with is too much for another person. Work with your doctor to make a pain management plan that works well for you. It may include both over-the-counter and prescription medicines. Talk with your doctor about how to safely use narcotic pain medicines.

Other ways to manage pain include using a heating pad, taking a hot bath, resting, or getting a massage. Physical therapy might help to relieve your pain if it can help you relax and strengthen your muscles and joints. Counseling and self-hypnosis may help. Also helpful are activities that keep your mind off the pain, such as watching TV and talking on the phone.

Caring for a Child With Sickle Cell Anemia

If your child has sickle cell anemia, you should learn as much about the condition as possible. This will help you recognize early signs of problems, such as fever or chest pain, and seek early treatment. Sickle cell centers and clinics can give you information and counseling to help you handle the stresses of coping with this serious, chronic condition.

Frequent Doctor Visits

Your child will need to see the doctor often for blood tests and to be checked for any possible damage to his or her lungs, kidney, and liver. It’s recommended that before age 2, children with sickle cell anemia see the doctor every 2 or 3 months. After age 2, children may need to see the doctor at least every 6 months.

Talk to your child’s doctor about your child’s treatment, how often the doctor should see the child, and the best ways to help keep your child as healthy as possible.

Preventing Infection

Call your child’s doctor if your child has a fever or if you notice any signs of infection, such as trouble breathing. Keep a thermometer on hand, and know how to use it. Call a doctor if your child has a temperature above 101 degrees Fahrenheit (38.5 degrees Celsius). To prevent infection, most children will be given:

Daily penicillin up to age 5.

A flu shot every year after 6 months of age.

A regular vaccination against pneumonia. (This also is given to children who don’t have sickle cell anemia.) Children with sickle cell anemia also get two doses of a stronger pneumonia vaccination after 2 years of age. Doses of this stronger vaccination are given several years apart.
Vaccination against meningitis after the age of 2.

Preventing a Stroke

Ask your doctor whether your child needs regular ultrasound scans of the head. Knowing the signs and symptoms of a possible stroke is important. These include a lasting headache, weakness on one side of the body, limping, or a sudden change in speech, vision, or hearing. It could even include changes in behavior.

Find Out When To Call the Doctor

Ask your child’s doctor what you should report to him or her right away. For example, you may be asked to call the doctor right away if your child has any signs of a stroke or infection. You may be told to call the doctor if your child has:

Swelling of the hands, feet, or stomach

Skin or nail beds that are suddenly pale or skin or eyes that have a yellow color

Sudden fatigue (tiredness) with no interest in his or her surroundings

Erection of the penis that won’t go away

Pain in the joints, stomach, chest, or muscles

School-aged children can often—but not always—take part in physical education or sports, but only after approval of the child’s doctor. Ask your doctor about safe levels of exercise for your child.

Caring for a Teen With Sickle Cell Anemia

Just as with any chronic condition, teens who have sickle cell anemia must manage their condition while dealing with the stresses of the teen years—peer pressure, sexuality, independence, education, and career goals. Specific stresses faced by teens with sickle cell anemia include:

Body-image problems caused by a delayed sexual maturity

Coping with pain and fear of addiction from using narcotic pain medicines

Living with uncertainty, because sickle cell anemia is unpredictable and can cause pain and damage to the body at any time

Ways to support teens with sickle cell anemia include teen support groups and family and individual counseling.

Key Points

Sickle cell anemia is a serious condition in which the red blood cells can become sickle-shaped (that is, shaped like a “C”).

Sickle-shaped cells don’t move easily through the blood. They’re stiff and sticky and tend to form clumps and get stuck in blood vessels. The clumps of sickle cells block blood flow in the blood vessels, causing pain, serious infections, and organ damage.

Sickle cell anemia is an inherited, lifelong condition. People who have sickle cell anemia are born with it. They inherit two copies of the sickle cell gene, one from each parent.

People who inherit a sickle cell gene from one parent and a normal gene from the other parent have a condition called sickle cell trait. People with sickle cell trait don’t have the condition, but they can pass the sickle cell gene on to their children.

Sickle cell anemia affects millions of people worldwide. It’s most common in people whose families come from Africa, South or Central America (especially Panama), Caribbean islands, Mediterranean countries (such as Turkey, Greece, and Italy), India, and Saudi Arabia.

In the United States, sickle cell anemia affects about 70,000 people. It mainly affects African Americans.

The signs and symptoms of sickle cell anemia are different in each person. Some people have mild symptoms. Others have very severe symptoms and are often hospitalized for treatment.

The most common signs and symptoms of sickle cell anemia are linked to anemia and pain (also referred to as a "sickle cell crisis").

Infection is a major complication of sickle cell anemia. Pneumonia, in particular, can be a life-threatening complication in children with sickle cell anemia. Routine treatment with penicillin and vaccinations are used to prevent infection in children.

Strokes are a major complication for children with sickle cell anemia. Routine screening and early treatment can prevent strokes.

Early diagnosis of sickle cell anemia is very important so that children who have the condition can get proper treatment. Screening tests for sickle cell anemia and sickle cell trait are done on newborn infants in most States. One blood test used to diagnose sickle cell anemia looks at how hemoglobin moves in an electric field. This is called electrophoresis, and it’s usually used to diagnose older children and adults.

Effective treatments are available to help relieve the symptoms and complications of sickle cell anemia, but in most cases there’s no cure. (Some researchers believe that bone marrow transplants may offer a cure in a small number of cases.)

Sickle cell anemia is treated with medicines, blood transfusions, and other treatments specific to certain complications.

Researchers are working to develop new treatments for sickle cell anemia, including gene therapy and safer and more effective bone marrow transplants.

If you have sickle cell anemia, take good care of yourself and see your doctor regularly.

If your child has sickle cell anemia, you should learn as much about the condition as possible.

This will help you recognize early signs of problems, such as fever or chest pain, and seek early treatment.

Glossary

DNA: this is the chemical which carries genetic information in the nuclei of cells.

Gene: this is a bit of DNA.

Chromosome: this is a strand of protein with a large number of DNA molecules attached to it. The number of chromosomes varies between different animals and plants. The full number in humans is 46 (23 pairs).

Alleles: these are different versions of a gene e.g. B and b see eye colour above.

Dominant: this is the allele which will be "expressed" in the phenotype if it is present as either a single gene or as two genes. e.g. B

Recessive: this is the allele which is only expressed if these are two such alleles e.g. b.
Co-dominance: this is when neither of two alleles is dominant to the other. Here there are three genotypes HH, HS and SS; each produces a different phenotype. Homozygous: this means having two identical alleles, e.g. BB or bb

Heterozygous: this means having a dominant and a recessive allele e.g. Bb. Genotype: this is what genes you carry e.g. BB, Bb or bb.

Phenotype: this is what you look like e.g. brown or blue eyes

Mitosis: this is a genetically exact division of a cell. Meiosis: this is a genetically inexact division of cell reducing the number of chromosomes to a half the normal number. This is what happens in the testis and ovary; meiosis produces gametes. Gametes: these are the sex cells i.e. sperms and eggs. Eggs are also called ova

Mutations: this is change or mistake in copying a gene. Most mutations result in recessive genes. The information in the DNA molecule has been corrupted and it will no longer produce the correct protein