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!!A+UkSv7jG/0 10/10/11(Mon)19:01 No.20501919Inheriting mutations:
Because
the gametes only have one set of genetic information, they need to
combine with another gamete for a second set of information. This is why
two sex cells (sperm and egg) combine to create a zygote. The zygote
created inherits one set of chromosomes directly from each parent. Any
mutations present in the chromosomes of a parent's gamete will become
part of the zygote. Because every cell that divides from the zygote is
created the same way as body cells are, they will all have the same set
of chromosomes as the zygote, and they will inherit the mutations as
well. Since all cells in a child descend from the zygote, any mutation
in a parent's gamete may become part of the zygote, and then part of
every cell in the child's body.
Because the child's sex cells
inherit their chromosomes from the child's body cells, and every body
cell should have the mutation, almost all the child's sex cells will
have the mutation. This means that their child should have the mutation,
and so on.
We know that body cells can mutate from exposure to
radiation or different chemicals, but now we may see that these
mutations can be passed on to all the cells that descend from the
mutated cells. Since the body cell can split into a sex cell, we know
that the mutations can be passed on to a sex cell, and from there to a
zygote, where the mutation will become part of almost every cell in the
child grown from the zygote.
We can see that the child can create
a line of children with the mutation. If somewhere along that line,
another mutation is passed on to a sex cell, another line may be created
with both mutations. This can happen over and over, with new lines
inheriting mutations from the one's they split from. The mutations then
'pile up' over millions of generations. This can result in a branch with
enough mutations that they end up seeming like a completely different
organism from those they descended from. |