The method of consolidation of family power is commonly practiced in other parts of the world, including India, where even today, relatives still prefer to marry into each other’s families.
This is all very well when it comes to consolidating family values and wealth. However, there is a downside when it comes to family health. Research on consanguineous marriages (i.e. marriages between blood relatives up to the third degree: brothers and sisters being the first degree, maternal and paternal uncles and aunts being the second degree, and first cousins being the third degree) has established that genetic, congenital and family diseases are also consolidated and perpetuated through marriages between close relatives. It is for this reason most countries frown upon marriages between relatives even upto the sixth degree of relationship.
Genetics and heredity
It was only in the 20th century that scientists could explain why children so often resemble their parents. The reason they do, is because parents pass on to their children blue prints of themselves, which are contained in every cell of their bodies, including the sperm and ova. These blue prints are carried in the genes, which exist in the nucleus of every cell. Every cell has a complete set of blue prints which contain a detailed genetic code of skin colour, hair, eyes, body type, inheritable disease etc.
But the sperm and ova contain only 50 percent of the blue prints. So when fertilisation takes place, the 50 percent of the father’s genes carried in the sperm merges with the 50 percent contained in the ova, making a 100 percent brand new life whose genetic blue print is an equal merger of both parents. Keep in mind that even while the gene contains 50 percent of the characteristics of each parent, it in turns contains 25 percent of each grandparent, 12 and a half percent of each great grandparent and so on. This is the basis of genetic inheritance.
The reason why no two children are exactly alike (except for identical twins fertilised from the same egg and sperm) is because the 50 percent mix of each parents is random, and the possible different genetic combinations are calculated to be a stupendous 64 million different possibilities! To complicate the picture even further, remember that in each male ejaculate, there are over a million sperms – and the repository of ova in the female exceed eight million in a lifetime, of which only one is released each month, and only a few are fertilised in a lifetime.
Genes do not only carry family genetic code but several new characteristics – good and bad – may be created within the parents’ lifetime prior to conception. These changes in the genetic code are called mutations and could be caused by a good and healthy lifestyle and diet, or by a bad environment and radiation etc. These mutations and changes in the DNA make each individual different and unique.
Genes are either dominant or recessive. For example, the genes for brown eyes and black hair are dominant, whereas the gene for blue eyes and blond hair are recessive. A dominant gene will always find expression over a recessive gene. For a recessive gene to find expression, it will need to be contained in the genetic code of both parents and passed on to the child. What further confounds the situation is the randomness by which dominant or recessive genes will be contained in the 50 percent genetic code passed on by each parent, which also include the grandparents’ contribution.
Besides inheritance from dominant and recessive genes, certain characteristics are specifically attributed to inheritance from the mother’s X chromosome. This remains ineffective or recessive in a daughter who comprises of two XX chromosomes, but is dominant and pronounced in a son who comprises of the XY Chromosomes – of which the X chromosome is inherited from the mother.
Keeping in mind that inbreeding and consanguineous marriages between relatives result in a common gene pool, here are few of the more prominent of the 1800 and more genetic abnormalities that can be passed down as a consequence:
- Dominant Gene disorders:
- Achondroplasia brings about dwarfism.
- Huntington’s disease is a brain disorder that causes involuntary movements and emotional disturbances.
- Hyperlipoprotenia is where due to inheritance, the blood lipid levels are double of normal, causing early heart ailments.
- Marfan’s syndrome is characterised by tall stature with eye and heart defects.
- Polycystic kidneys where there are multiple cysts in the kidneys, causing them to fail.
- Recessive Gene disorders:
- Albinism is the lack of pigment and colour to the skin, hair and eyes.
- Acheiropody, the lack of hands and feet.
- Deaf mutism, or deafness from birth.
- Retinitis pigmentosa is progressive blindness leading to loss of vision.
- Thalassemia is dysfunction of red blood cells, causing low oxygen intake and severe fatigue.
- Sickle cell anemia where the red blood cells take on a sickle shape, malfunction, clump together and block circulation.
- X linked Chromosome disorders:
- Colour blindness, or inability to see the colours – red and green etc.
- Hemophilia, which is known as the royal disease, is the inability of the blood to clot. This affects males mostly.
- Muscular dystrophy is the progressive fatal wasting of muscles.
- Fragile X syndrome is characterised by a large head, reduced intelligence.
- Chromosome variation disorders:
- Down’s syndrome: mental retardation with characteristic round face and thick tongue; also referred to as Mongolism.
- Turner syndrome affects only females, with impaired fertility and congenital heart defects.
To see how a disease can travel through a family tree, one just has to look at hemophilia that ran through the royal families of Europe during the late 1800s and early 1900s. Hemophilia prevents blood from clotting, meaning that any small injury could actually cause a person to bleed to death. Because this hereditary disease is carried on the X chromosome, it is much more common in males, who have chromosomes XY. Females (XX) will usually have one X still disease-free and do not show symptoms, but become carriers, who can then pass on that diseased X gene to some of their male children.
Queen Victoria turned out to be a carrier of this disease and passed the defective X chromosome to three of her nine children through whom resultant deaths followed into various royal houses across Europe. Through her daughter Alice’s marriage, the disease reached the royal families of Germany and Russia. Through her youngest daughter Beatrice, who was another carrier of the disease, it reached Spain. Leopold, the one hemophiliac son (XY) of Queen Victoria, passed that troubled X chromosome to only one daughter. Alice then carried the disease to her son Rupert – who died young. Thus the disease persisted for three generations.
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