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Sex Chromosomes and Sex-Linked Genes (Paperback, Softcover reprint of the original 1st ed. 1966)
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Sex Chromosomes and Sex-Linked Genes (Paperback, Softcover reprint of the original 1st ed. 1966)
Series: Monographs on Endocrinology, 1
Expected to ship within 10 - 15 working days
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Natural selection operates among individual organisms which differ
in their genetic constitution. The degree of hereditary variability
within a species is greatly enhanced by cross-fertilization.
Indeed, the mechanism of sexual reproduction occurred very early in
evolution, for it is seen today even in bacteria. In Escherichia
coli, fertilization occurs by passage of the single chromosome from
the male into the female bacterium (LEDERBERG, 1959). In
multicellular organisms, the separation of germ from soma, and the
production of haploid gametes became mandatory. The gametes were of
two types. One, extremely mobile, was designed to seek out and
penetrate the other, which loaded with nutrients, received the
mobile gamete and intiated the development of a new individual. The
foundation for true bisexuality was thus laid. In the primitive
state of bisexuality, whether an individual is to be a
sperm-producing male or an egg-producing female appears to be
decided rather haphazardly. In the worm, Banelia viridis, the
minute males are parasites in the female. Larvae that become
attached to the proboscis of an adult female become males, while
unattached larvae sink to the bottom and become females (BALTZER,
1935). The more sophisticated state of bisexuality was initiated by
setting aside a particular pair of chromosomes for specialization
and making either the male or the female a heterogametic sex. Sex
chromosomes as we know them were thus born.
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