Flashcards in 9.28 Gametogenesis Deck (19):
in meiotic division, the cells go from 2n to ___, then after the first cell division is is ___, and after the second, it goes to ___
4n (92 chromosomes)
2n (46 chromosomes)
1n (23 chromosomes)
in the follicle, an oocyte is surrounded by __________ cells, which secrete _______ that become the zona pellucida
what is the zona pellucida? why is it important?
it is a jelly-like coat around the oocyte, which is a central docking region for sperm
in oogenesis, one precursor cell gives rise to _____ ovum (egg) and 2 or 3 ____________
oocytes start primary meiosis before birth, primary meiosis is completed only upon ________. Now, the oocyte is __n and there is a _______ that is also __n
polar body that is also 2n
During _______, the second meiosis occurs, and is only completed upon ________. Now, we have a __n oocyte.
in spermatogenesis, one germ cell gives rise to ____ sperm.
spermatogenesis takes place in _______________ of the testes. They start on the outside, mature, and get released into the _____. _____ cells help this process.
Down's syndrome is caused by:
an extra copy of chromosome 21.
The extra copy of chromosome 21 in Down's syndrome resulted from abnormal _______ division
Patau's syndrome is also called __________. It is a copy in chromosome ___ and is usually not compatible with life.
This disease occurs when a single X chromosome is inherited instead of 2.
what are some of the manifestations of Turner syndrome?
short stature, webbed neck, reduction in secondary female characteristics, sterile.
an extra copy of the X chromosome in males (XXY)
what is the translocation between Ch13 and Ch14 called?
in Robersonian translocation, what chromosomes are rearranged? They make a _______________ at the centrosome.
13 and 14
fused chromosome at their centrosome.
People with Robersonian translocations are usually _____ since it can cause uneven meiosis.
what are some main causes of male infertility?
absence of sperm, reduction in number, or production of defective sperm