The without any direct harmful phenotypic effect

The incidence of
deletions of Y chromosome had found in 2 patients (1.2%) in our study was lower
than that given in literature (3-18%) (13). It increases with the severity of
spermatogenic defects. Y chromosome abnormalities, particularly the deletions
involving long arm of the Y chromosome lead to azoospermia and male
infertility. This type of deletion does not appear to impair spermatogenesis in
some males, but leads to infertility in others. The simple explanation for
these observations is that there is a key locus (or loci) close to the boundary
between genetically inert heterochromatin and Yq euchromatin. In some males,
the removal of this locus by more extensive deletion causes infertility. Such
large structural changes to the Y chromosome might disturb normal pairing and
segregation with the X chromosome during meiosis, is the cause of
spermatogenetic failure in these males. The vast majority of deletions of Y
chromosome associated with complete absence of germ cells (azoospermia) or
severe oligozoospermia are cytogenetically undetectable 13,17,18,19

      Heterochromatic
polymorphic chromosomal variants also well studied both in the infertile men
and normal population. The frequency of these variants in infertile men was
higher in our study (31.2%), but remained similar to that in the control group
(35%) (Table IV). It was also coincidental with the literature data in
infertile males (4.7-56.8%) and in fertile males (32.7%) 13. Polymorphic
variants are usually considered as normal variants inherited from one generation
to another with low mutation rate and without any direct harmful phenotypic
effect due to the scarcity of protein coding region in them. However, the
increased polymorphic variants may have some clinical significance and
associated with clinical anomalies. The detrimental effect of variants may be
not direct to phenotype but indirect through the disturbing spermatogenesis and
causing the death of germ cell resulting in infertility or children with
congenital anomalies 22,23.

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A large
heterochromatic block in the pericentrometric region of chromosome 1 may affect
the pairing of chromosomes causing meiotic arrest, death of germ cells and
infertility 15. It is suggested that 9 qh+ could be in association with
repeated spontaneous miscarriages, stillbirth, multiple congenital
abnormalities and chromosomal abnormalities in aborts and offspring. However,
the result of our study and some of other authors do not support this report as
of high incidence of  9qh+ found both in
normal (10%) and infertile males (7.2%) 24,25,26.