Chapter 7
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Part 1: Genes, Chromosomes, and Heredity
Sex Determination and Sex Chromosomes
Review
reproduction involving meiosis and
is important in many multicellular
organisms.
Chlamydomonas
gametes are
and consist of two
types,
though there is no genetic difference between the
types.
Maize
is a
(sporophyte contains both male and female parts) plant that exhibits
alternation
of
, with a dominant
stage and a
stage.
Sexual development in the
nematode
Caenorhabditis elegans
is determined by the
ratio
of
chromosomes to sets of
.
In the
mode
and
mode
of sex determination, gametes from the
sex determine the sex of the progeny.
Humans possess
chromosomes:
22 pairs of
and two
chromosomes.
of the X chromosomes (failure to segregate) during
meiosis
results in sex chromosome
such as
syndrome
and
syndrome.
Other sex chromosome abnormalities include
and
aneuploidies.
In humans, the
region on the
chromosome
is necessary for male development.
In mammalian females, one of the two X chromosomes in each cell is randomly
during embryonic development and can be seen as a compact
body.
A female
heterozygous
for an X-resident gene may
exhibit
a
phenotype.
Sex determination in
Drosophila
depends on the
of
chromosomes
to autosomes; loss of an X during development can result in a bisexual
fly
called a
.
Many reptiles exhibit
-dependent sex determination (TSD),
which
can be
one
of three
modes.
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Oct 7, 2008
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