Episode 8: The genetic effect of marriage between relatives (2/5)
Dr. Al Baarr: "As
the genetic characteristics may be prevalent (dominant), or may be receding
(recessive), the recessive characteristics will not be apparent, neither in the
father nor in the mother. If it happens that the father and the mother both
carry one of these recessive traits; a quarter of their children - almost – will
show these recessive traits, clearly evident, and that is due to presence of the
two characters in both of them.
This is what makes a marriage between relatives (consanguinity) show the characteristics and recessive diseases, which were hidden, since both the father and the mother who are consanguineous in descent carry a lot of common and recessive characters- so they do not appear on them – Therefore, if they are joined in marriage, the probability of the emergence of these recessive characters increases greatly.
For instance, some genetic diseases that are rare in the community, the probability of their manifestation in an exogamous couple is no more than one in a thousand, while the possibility of the emergence of this rare genetic disease increases to (35%) when the couple are first cousins through their paternal or maternal uncle or aunt.
Recessive genetic diseases are very abundant, including diseases which confer defects in the metabolic process (metabolism) (inborn error of metabolism), such as the disease of Wilson (Wilson’s disease), the disease of Tay Sachs (Tay Sachs’), inherited leprosy (albinism), black urine disease (alcaptonuria), and the number is more than one hundred diseases known to specialist physicians.
Therefore, genetic diseases, especially those with recessive traits, occur clearly and with a greater proportion in consanguineous marriages "(20).
While Dr. Omar Al Alfi mentioned two principles for genetics, namely:
The first one: If the source of the genes in intermarriage is divergent, the offspring will be strong. This principle has been deduced from the results of mating experiments between animals, as well as from pollination experiments in plants.
The second one: If both the father and the mother carry the same defective gene, this will allow the recessive genetic disease to be expressed in the offspring with an incidence of one in four in each occasion, and the probability that both the father and the mother carry the same defective gene increases with the degree of closeness of kinship between them.
He stated that - in many studies already conducted in the State of Kuwait: - it has been show that the incidence of premature births is higher in consanguineous marriages (9.89%) than in marriages between non-relatives (7.46%).
The average birth weight in consanguineous marriages (3274 g) is lower than the average weight in marriages between non-relatives (3326 g).
The incidence of some genetic diseases in consanguineous marriages is higher than in marriages between non-relatives. The most important of these diseases - in terms of scientific importance - is the kind of mental deficiency called (Mongolism), where there were (14) cases among (3989) consanguineous marriage– i.e. a ratio of (3.5‰) vs. (6) cases among (7436) marriage between non-relatives – i.e. a ratio of (0.8‰).
What is new in this research is that the disease (Mongolism) results from a defect in the division of chromosomes, and the scientific conclusion here is that this case is influenced by a recessive gene, and thus its incidence increases among consanguineous marriages (21). (End of quote).
Hafez Youssef Moussa reported, according to Al-Ahram Newspaper, that Dr. Fuad El-Sherbini (22) carried out a study, which found out that consanguineous marriage resulted in the affection of children with disorders of the immune system and allergies, which weaken the resistance of children to microbes. The most important diseases are (Mediterranean anaemia), a kind of deficiency in haemoglobin (anaemia), diabetes, gout, chemical disorders and low vision. These are among the diseases which appear in the second generation directly. The proportion of hereditary low vision reached (50%) of the total cases of low vision. Children are genetically predisposed to heart disease, bronchial asthma, epilepsy and deafness. It is not a condition that one of the parents is affected, but their kinship is enough for the child to acquire what the ancestors had.
Among the studies carried out by the Higher Institute of Health, a study which concluded that cases of pre-eclampsia, and the mortality in toddlers and nursing infants are on the increase in consanguineous marriages compared to other (forms of marriage) (23). (End of quote).
(20) The Creation of
Man between Medicine and the Quran (p. 154).
(21) Paper: (Marry afar and do not become sickly), already mentioned when elucidating those who inferred upon this Statement.
(22) The former head of the Department of Maternal and Child Welfare at the Higher Institute of Public Health, Egypt.
(23) Sex between Islam and Secularism (p. 321). The author said: these studies were conducted in Egypt, quoting Al-Ahram Newspaper number (36451) of 26.09.1986 A.D.