Genetics & Genotype

Genetics & Genotype

Genetics is the core of our existence; you have dark skin, brown eyes or large hands because of your genetic make-up. You get your genes from your parents at conception and it is an intricately, calculated blend of features from both of them. Advances in medical science means that many couples can know if their foetus is carrying a defective gene even before birth. You may not think that we care much about this type of tests here but almost every woman is given the opportunity to undergo an anomaly ultrasound scan at about 18-22 weeks (4-5months) into her pregnancy. The anomaly or 21-week scan, checks your baby’s growth, her position as well as possible fetal abnormalities e.g. down’s syndrome. Since most women fall pregnant before going to see a gynaecologist, most genetic testing is done during pregnancy. The test is usually offered optionally and is not 100% conclusive but it can predict the probability of having a baby with a genetic defect. Some races/ ethnic groups are more prone to certain genetic diseases than others. People of black or black-related origin may run a higher risk of carrying the following genes:

Sickle Cell Anaemia

Every human being has red and white blood cells. The red blood cells carry oxygenated blood around the body while the white blood cells defend the body against diseases. Red blood cells normally look like circular, round disks but occasionally they are sickle-shaped (crescent shaped). If a person does not have sufficient red blood cells, then that person is said to be anaemic (that is, has anaemia). The circular shape of the red blood cell aids its mobility round the body. When red blood cells are sickle-shaped, they can easily get stuck in blood vessels and this may prevent proper blood flow to major organs. This situation can cause immense pain and it is not uncommon to see people living with sickle cell in a lot of pain –especially in their limbs.  The sickle shape of the red blood cells also singles them out for destruction by the body’s white blood cells; which sees them as enemies. This coupled with the fact that sickle cells have a very short life span (a little over 10 days) means that there can be periods of  short supply of the red blood cells in the body, especially if the body is unable to replenish the lost cells fast enough. Anaemia which is as a result of the sickle shape of the red blood cells is called Sickle Cell Anaemia.

Symptoms of sickle cell anaemia usually show up when an affected child is between 4-6months old. Sickle cell anaemic persons may have:

  • A crisis which may be triggered by: Malaria fever; a change in normal conditions (weather); low fluid intake; malnutrition; etc.
  • Pain in different parts of the body especially in the neck, bones/joints and stomach which may range from mild to severe.
  • Tiredness
  • Increased risk of infections
  • Stunted growth
  • Jaundice –yellowish eyes
  • Painful swellings in hands and feet
  • Reduced life expectancy

Sickle cell genes are passed on to children by parents who are carriers of the genes. Some experts believe that there is a link between the sickle-shaped red blood cells and the carrier’s resistance to Malaria. The red blood cells are taught to have originally mutated to the sickle shape as the body’s way of self-preservation against malaria. The genes are in turn, preferably selected for this reason as well.

When both parents each pass on a sickle cell gene to a child (that is the child gets two (S) genes from both parents), then that child will have sickle cell anaemia or haemoglobin SS disease (HbSS). If the child gets one sickle cell gene (S) and a normal gene (A) from both parents, then that child has a sickle cell trait. People with sickle cell traits are just carriers of the defective genes and normally do not have the sickle cell disease. They can however pass on the sickle cell gene to their own children.

Sickle cell diseases may also be caused by other abnormal, haemoglobin types e.g. haemoglobin C or β- Thalassemia. This occurs when a child gets a sickle cell gene from one parent and some other type of defective gene from the other parent.

Sickle cell anaemia is normally managed with prescribed painkillers and amoxicillin (or penicillin) antibiotics. In more serious instances blood transfusion and bone marrow transplant may be required. A bone marrow transplant is more complicated than the other forms of treatment and requires a donor with stem cells or a bone marrow that matches the recipient’s.

Albinism

We all look different. The colour of your skin, eyes and even hair is different from the next person. The substance in the body that is responsible for skin, hair and eye pigmentation or colour is called Melanin. Normally, people with dark skin (e.g. people of African descent) have higher melanin than people with fairer skin types (e.g. Caucasians). Albinism is a genetic disorder which is caused by the body’s inability to produce sufficient melanin.  Melanin, amongst other things, protects the skin from the harsh rays of the sun and it is also helps to protect the iris. People living with albinism need extra protection due to the insufficient amount of melanin. People with albinism are normally referred to as albinos. Albinism cannot be passed on to children if they get one normal pigment gene and an albinism gene from their parent. It can only be passed on if they get two albinism genes from their parents.

Albinism does not affect a person’s mental or physical state. Albinism is not contagious. And it is definitely not witchcraft or a curse. Many albinos go on and have gone on to live normal productive lives.

Albinos can protect themselves by:

  • Spending limited periods in the sun,
  • Using effective sun glasses, hats and plenty of sunscreen lotion with a Sun Protective Factor (SPF) of at least 15 and up to 70. SPFs protect the body from the harmful ultraviolet rays of the sun.
  • Using natural oils like shea butter and extra virgin olive oil on their skin to keep it supple and healthy.

Autism

Autism is a combination of developmental disorders which may be evident as poor or difficult communication, poor social interaction and repetitive motions. It may be diagnosed as early as infancy (if impaired speech is evident amongst other symptoms). It is however more pronounced in toddlers aged 18 to 30 months (especially boys) and proper diagnosis can be made at this age. Although autism currently has no cure or known cause, the symptoms can be managed and treated, with early detection improving chances. It is generally believed to be a congenital brain structure abnormality.

A child MIGHT be autistic if at 18 months:

  • He can’t answer to his name.
  • Finds it really difficult to learn new words.
  • He doesn’t normally respond to a hello or good bye wav.
  • He doesn’t return smiles.
  • He becomes unreasonably upset, resists or gets confused if there is a change in normal routine, food or activity.
  • He has poor social interaction with other children.
  • If he used to babble as an infant but can’t currently manage any words.

There have been claims that some vaccinations are linked to a rise in autistic cases; current research as at the time of this write-up showed that these claims have been disproved. While delayed development in a child may be a sign of autism it does not necessarily mean that the child is autistic. Do not confuse delayed developmental milestone achievement with autism, children grow differently. Proper diagnosis can only be made by a qualified medical practitioner.

Down's syndrome

At conception, 46 chromosomes are passed on to the foetus (23 chromosomes from each parent). Down’s syndrome is a genetic disease which occurs when an extra chromosome called chromosome 21 is passed on to a child thereby increasing the total number of chromosomes to 47. It can be detected even while a child is in the womb. A genetic test called Chorionic Villi Sampling is used to detect it during pregnancy. The health issues associated with Down’s can also be treated with early detection and proper care.

Children with Down’s syndrome have distinguishable features which include slant eyes, small ears and protruding foreheads. While some children living with Down’s syndrome may have respiratory and heart diseases or mental disorders, some others have little or no health conditions.

As a woman grows older, the chance of having a child with Down’s syndrome increases. Though many women over 40 have normal children, women over 35 should see a medical practitioner when planning to conceive for proper health assessment.

We would like to add that children with Down’s syndrome can and do grow up to live very productive lives and like any other child, they deserve the very best and should not be abused, abandoned or neglected.

Key facts about Genetic disorders

  • A baby cannot inherit a genetic disease if both parents are non-carriers of the genes.
  • A baby has a 1 in 4 chance (25%) of having normal genes, if both parents carry the genetic trait (i.e. if both of them are carriers).
  • A baby has a 1 in 4 (25%) chance of getting the genetic condition, if both parents have the genetic trait (i.e. if both of them are carriers).
  • A baby has a 2 in 4 (50%) chance of being a carrier if both parents have the genetic trait (i.e. if both of them are carriers).

Apart from genes, some other things which may predispose a baby to genetic disorders or birth defects are:

  • Unhealthy levels of exposure to toxic chemicals, radiation, fumes or smoke.
  • Drug abuse or alcohol use during pregnancy.
  • When there are close relatives in the family with a genetic disease.
  • When the parents are closely related by blood.

While tremendous advance has been made in genetic science and engineering, many people still live with genetic disorders. Children born with genetic disorders have the same rights as anyone else. Their condition should never be a reason for discrimination, maltreatment or injustice. They deserve love and care like any other child and with proper nurture and care; they can grow up to live productive lives.


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