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The man-Sexuality
Determining sex in living creatures who
have two dissimilar sexes is done through
certain mechanisms.Before explaining the
mechanism involved in determining sex in
human beings,two points should be dealt
with in connection with the transfer of
traits from parents to offsprings and cell
division.
A - inside the nucleus of the cells of all
living creatures there exist tiny bodies
called chromosomes,which are in fact sites
for genes.The types and orders of genes,like
codes,also keep in themselves characteristics
of creatures.Chromosomes are usually in pairs
and their number differs in various
creatures.In human each somatic cell has 64
or 23 pairs of chromosomes.22 pairs of these
are non-sexual and the remaining pair is
human sexual chromosomes human . Sexual
chromosomes are clearly distinct from other
ones.In females both sexual chromosomes are
identical and are shown as XX,but in males
one of them is much smaller than the other
one )Y(,and is shown as XY.
B - generally,two types of cell divisions are
distinguishable in living creatures :
1.mitosis division,in this kind of division
which is generally seen in non-sexual cells
(somatic(,each cell producess two cells of
its own type , which from all respects,
including the number of chromosomes,are
similar to the original cell.
2 - meiosis division,in this kind of division
which is generally carried out in sexual
cells and when male and femal gamets are
produced,each original cell produces 4 cells
with half as many chromosomes as that of
the original one.In man,as a result of such
division,each gamet will have 23 chromosomes.
Otherwise,following the pairing of male and
female gamets,the person evolved would have
a cellular chromosomes twice as many as that
of his / her parents'.
Considering the a foresaid,the mechanism with
which human sex is determined is taken up.
During the process of sexual gamets
production,men produce two kinds of gamets
(sperms(,half of which carry X chromosomes
and the other half carrying Y chromosomes.
Unlike men,gamets produced by women) ovum)
all have X sexual chromosomes . During
fertilization if an X carrying chromosome
fertilizes an ovum,the offspring would be
a girl) XX(;and if the ovum is fertilized
by a Y carrying chromosome,the baby would
become a boy )XY( . In human being sex is
determined during the fertilization process,
and man's sperm has a decisive role.
Here although in normal situations
fertilization and sex determination seems
quite accidental ,now a days in the light
of vast studies carried out in this regard,
many factors have been considered to be
effective indetermining whether the offspring
would be a girl or a boy . For example
scientists believe that the size and volume
of the head of the sperms carrying X sexual
chromosomes differs from that of those
carrying Y sexual chromosomes.Therefore,the
desired sperm can be fecundated with ovum.
Sometimes in meiosis division,all or more
chromosomes accumulate at one pole instead
of being evenly distributed at the two cell
poles;therefore the person evolved is
different from normal man from the point of
view of chromosomes;the result of which is
the occurance of severe changes in the person
and usually leads to infertility . Such
abnormalities as Down's syndrome )mongolism)
and Turner's syndrome are all complications
of this irregularity in chromosome numbers.
It should be noted that not all living
creatures follow this sex determining
mechanism.For instance in birds and
butterflies,unlike in man,the female produces
two gamets.In addition,in some creatures sex
is determined through having one or two
sexual chromosomes.In locusts,for example,
males have one sexual chromosome and 32
chromosomes altogether,while females have
2 sexual chromosomes,24 altogether.
