Many simple
one celled animals are unisex: each one reproduces itself by
splitting into two cells identical with their parent. man and
other complex animals breed differently. Such species contain
males and females. Special cells from a male and female fuse to
produce a cell that shares hereditary material from both its
parents. This cell multiplies by splitting to give rise to an
adult organism identical with neither parent. So sexual
reproduction produces countless permutations of individuals.
This means there are likely to be some able to endure changes to
their surroundings that kill most of the rest. Sex then, is an
ingenious biological device to help a species to survive in a
changing world.
The blue print
determining which sex you are was laid down in you are was laid
down in your parents chromosomes - packages of hereditary
material contained in every body cell. by determining how each
cell grows, your chromosomes also help control such hereditary
traits as body build and color of hair and eyes. the nucleus of
each ordinary cell holds 23 pairs of chromosomes . When a cell
splits in two to build or repair body tissue its chromosomes
double up and divide, so each new daughter cell also receives 23
pairs. but sperm ( male sex cells) and eggs or ova (female sex
cells) are different.
A Girl or a
Boy
When the body
makes sex cells each gets only 23 chromosomes, one of which
carries a sex - determining factor. All eggs and one in two
sperm have what is called an X chromosomes, which carries
the "female" factor. The other sperm have a Y chromosome
carrying the ' male ' factor.
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Girl |
If an egg is
fertilized by a sperm with an X chromosome the
resulting child will have two X chromosomes (XX) and
be female.
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Boy
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If
fertilization is by a sperm with a Y chromosome, the
child will have one X and one Y chromosome (XY) and
be male.
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Know
the Fact |
In the society
of developing countries like Bangladesh a common feature is
that if a woman gives birth to more than one girl baby, often she has to
face physical and mental torture by
husband and his family as if she is the only responsible
for it.
But
what science
of human biology says is that whether a girl or
boy will be born completely depends on male
sperms that contain both chromosome X
( female factor)
and Y( male factor) whereas woman's egg contains
only X ( female factor) chromosome.
So, know
the science , agree with the truth and act
logically.
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Rare
Combinations
Rare errors in the
reassortment and recombination of chromosomes either during sex
cell formation or fertilization result in chromosomal sex
abnormalities, of which the following are examples.
An XXX combination
results in a normal looking but possibly infertile female.
If there is
one X but no Y chromosome ( XO), the result is an
infertile female with sex organs that fail to mature.
An XYY
combination results in a male with normal sex organs, but
perhaps with other problems.
Combinations
such as XXY or XXXYY produce males whose sex
organs remain immature and who may develop female secondary
sexual characteristics at puberty.
