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The Genetic Aspects of Infertility

Infertility or the inability to reproduce, affects males and females as well. It is caused by numerous factors such as a trinucleotide repeat expansion in the androgen-receptor gene in males, or a luteinizing hormone deficiency in females (Lee SL, et al, 1996; Dowsing AT, et al., 1999; Nachtigall LB, et al., 1997).
In the past, the causes of infertility were unknown. This is due to the fact that symptoms are hardly ever detectable. Most infertile individuals do not experience any symptoms at all. The small percentage that does show symptoms is very likely to receive an incorrect diagnosis. This occurs because the symptoms are very common to other illnesses as well. Symptoms such as loss of strength, and fatigue are common to many different conditions (Nachtigall LB, et al., 1997).
This disease was believed to be predominant in females. This assumption is incorrect, since males show the highest percentage of infertility in comparison to females.
Due to the complexity of spermatogenesis, the process through which millions of sperm cells are produced, the probability of defective sperm is higher than that of an egg in the female reproductive cycle. For spermatogenesis to be successful it requires the presence of androgens, and a functional androgen receptor. This androgen-modulated, DNA-binding protein regulates transcription of androgen target genes.
Since the androgen-receptor gene was isolated and cloned, mutations in this gene have been associated with various disorders including complete androgen insensitive syndrome, various motor neuron diseases, and prostate and ovarian cancers as well. Many phenotypically normal men have abnormalities of the androgen receptor. These infertile males are more likely to have longer than normal CAG (a trinucleotide) repeats in the androgen-receptor gene than fertile males. This elongation is responsible for spermatogenic defects as well as reduced sperm count. Lower numbers of CAG repeats in th…

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