Sex Chromosomes & Sex Linkage Flashcards
(45 cards)
not every organism has ____
sex chromosomes or even separate sexes
monoecious
in many plants and animals, every individual is both male and female
1 individual makes both male and female gametes
dioecious
organisms where there are separate males and females
all vertebrates are …
dioecious
in lower vertebrates however, males and females are not high differentiated
if sexes are not highly differentiated, then
there may be no special sex chromosomes
species with highly differentiated sexes also have differentiated _____
sex chromosomes
sex in humans is typical of …
placental mammals, in its biology, genetics, and cytogenetics
XX makes
females
XY makes
males
nonsex chromosomes are called
autosomes
humans have __ pairs of autosomes and __ pair of
autosomes, sex chromosomes (either XX or XY)
the X is …
big and metacentric
centromere near the middle
the Y is …
small and acrocentric
centromere very close to the end
X and Y act as a …
pair of homologs
even though they look different
what happens to X and Y in meiosis?
form a bivalent but only at the tips
psuedo-autosomal regions
Y pairs with X only in these regions on the tips
non-recombining region
male-specific region
located between the tips of the Y chromosome
do X chromosomes in the female recombine with each other?
yes, just like a normal pair of autosomes
they make a “normal” bivalent where recombination can happen anywhere along the length
chromosomal sex determination ensures..
equal numbers of males and females
SRY gene
found only on the Y chromosome on the short arm
near the end of the non-recombining region of Y
responsible for initiating male development
TDF
testis-determining factor
SRY makes
TDF protein
in the presence of TDF….
the testis-determining facror turns gonads into testes instead of ovaries
is SRY a dominant gene?
yes, only one copy makes you male
