Lecture 2/19

Question 1

what is oogonia?

Answer 1

diploid germ cells in ovaries of female embryos

Question 2

do oogonia divide by mitosis or meiosis?

Answer 2

mitosis, to make 7 million oocytes during fetal development

Question 3

what happens to oogonia in an embryo that don’t die by birth?

Answer 3

they enter and arrest in meiosis i to become primary oocytes and the chromosomes decondense

Question 4

what happens to oocytes starting at puberty?

Answer 4

once a month, hormonal stimulation causes one oocyte to recondense its chromosomes and complete meiosis i and starts meiosis ii

Question 5

is the DNA content the same between daughter cells after meiosis i for an oocyte?

Answer 5

yes, but one cell gets all cytoplasmic content (secondary oocyte) and the other is mainly nuclear (first polar body)

Question 6

does a secondary oocyte finish meiosis ii if it’s fertilized?

Answer 6

yes, and produces a mature ovum and a second polar body

Question 7

does a secondary oocyte finish meiosis ii if it’s not fertilized?

Answer 7

no, it arrests in metaphase of meiosis ii

Question 8

can mistakes occur from meiotic arrest at prophase i?

Answer 8

yes, there may be chromosome separation errors like trisomies

Question 9

does the oocyte develop in isolation?

Answer 9

no, it is within the primary follicle/follicular cells

Question 10

what happens to the corpus luteum if no fertilization occurs?

Answer 10

it degenerates

Question 11

what happens to the first polar body during/after meiosis i?

Answer 11

it dies

Question 12

what happens to the second polar body during/after meiosis ii?

Answer 12

it dies

Question 13

in what circumstance does a germ cell in women finish meiosis ii? when does it not finish?

Answer 13

it finishes if the egg is fertilized, if unfertilized it is released as is

Question 14

what are the cells called on day 1 after meiosis ii is finished in a fertilized egg?

Answer 14

there are 2 blastomeres

Question 15

what are the cells called on day 2 after meiosis ii is finished in a fertilized egg?

Answer 15

there are 4 cell blastomeres

Question 16

what are the cells called on day 3 after meiosis ii is finished in a fertilized egg?

Answer 16

there are 8 cell blastomeres

Question 17

what are the cells called on day 5 after meiosis ii is finished?

Answer 17

inner cell mass (becomes embryo) and approx 16-32 cells in the blastocyst

Question 18

what does the inner cell mass of the blastocyst become?

Answer 18

embryo

Question 19

what do the cells around the inner cell mass of the blastocyst become?

Answer 19

placenta and extraembryonic matter

Question 20

what are spermatogonia and where are they found?

Answer 20

diploid germ cells found only in the testis

Question 21

what happens to spermatogonia after puberty? what do they become?

Answer 21

meiosis begins and they become primary spermatocytes

Question 22

is division symmetrical for spermatocytes?

Answer 22

yes

Question 23

what is the product of meiosis i for spermatocytes?

Answer 23

two secondary spermatocytes

Question 24

what is the product of meiosis ii for secondary spermatocytes?

Answer 24

2 spermatids

Question 25

are all sperm Y?

Answer 25

no, an equal number of X and Y sperm are produced

Question 26

how long does spermatogenesis cycle take?

Answer 26

48-60 days

Question 27

for each spermatocyte, what is the product of a full cycle of symmetrical meiosis?

Answer 27

4 haploid sperm

Question 28

does mitosis stop in men when meiosis begins?

Answer 28

no, they both continue to occur throughout adult life

Question 29

when are mistakes in DNA replication fixed in gametogenesis?

Answer 29

proofreading, and the cell cycle is stopped until the correction is made

Question 30

what happens to a cell whose mistake in DNA replication isn't corrected?

Answer 30

it is slated for cell death

Question 31

what happens to a cell with a mistake from DNA replication if it's not corrected and doesn't die?

Answer 31

mutation in sperm or egg (every cell in the fertilized egg will have the mutation)

Question 32

what happens if there's a mistake in mitosis?

Answer 32

mitotic arrest until the mistake is corrected

Question 33

what happens to a mistake that isn't corrected in mitosis?

Answer 33

aneuploidy (wrong number of chromosomes) though this isn't often seen in the germline

Question 34

what happens if there is a mistake in meiosis (i or ii)?

Answer 34

cell divisions are arrested until corrected

Question 35

what happens if there is a mistake in meiosis (i or ii) that doesn't get corrected?

Answer 35

incorrect ploidy, uncorrected translocations, etc.

Question 36

what is -somy?

Answer 36

ONE chromosome (ie. trisomy 21 means there are 3 copies of chromosome 21 and all other chromosomes are normal)

Question 37

is monosomy viable?

Answer 37

only for chromosome X (Turner's syndrome)

Question 38

which germline are more de novo mutations found in with age and why?

Answer 38

male (XY) bc DNA repair mechanisms get turned off at some point in sperm

Question 39

are trisomies usually viable?

Answer 39

no, they usually die after birth if they are born alive (except for things like trisomy 21)

Question 40

do you lose genetic information in the error of reciprocal translocations?

Answer 40

no

Question 41

do you lose genetic information in the mistake of non-reciprocal translocation?

Answer 41

yes, an entire arm of one chromosome fuses to an arm of another chromosome (the remaining half-chromosome disappears)

Question 42

what kind of chromosome tends toward nonreciprocal translocation?

Answer 42

the ones with short arms

Question 43

what is a robertsonian translocation and does it result in genetic information getting lost?

Answer 43

an entire chromosome is translocated to another chromosome, no info is lost

Question 44

what happens when translocated chromosomes undergo meiosis?

Answer 44

the homologous chromosomes can't pair correctly in meiosis i

Question 45

what is mosaicism?

Answer 45

some cells have the correct number of chromosomes, others may have an incorrect number due to mitotic mistakes

Question 46

what is chimerism?

Answer 46

people who have cells that originated from different sources

Question 47

what is micro-chimerism?

Answer 47

exchange of cells between birth mother and XY fetus or between fraternal twins when one twin dies