Lecture 24 - Female reproductive ageing

Question 1

what are the 2 ‘ticking ageing clocks’ in female reproductive ageing?

Answer 1

ovarian and chromosomal ageing

Question 2

name the 3 reproductive consequences of transmitting the incorrect number of chromosomes

Answer 2

embryos arrest before implantation = infertility, miscarriage, birth defects

Question 3

after how many days following fertilisation of the egg does implantation occur?

Answer 3

5-6

Question 4

which trisomy is the most common cause of miscarriage?

Answer 4

trisomy 16

Question 5

which trisomy is associated with edward’s syndrome?

Answer 5

trisomy 18

Question 6

is it better to rescue the age related decline in fertility by assisted contraception or by donated eggs from younger females?

Answer 6

donated younger eggs

Question 7

what happens to the stock of oocytes throughout life/ovarian ageing? how many at start vs end?

Answer 7

depletes throughout life, start with 1 million at birth and 1000 post-menopause

Question 8

what does ovarian ageing occur in parallel with?

Answer 8

the increase of oocyte aneuploidy

Question 9

bivalent chromosomes must remain intact for decades until they are ready to progress into which stage of meiosis?

Answer 9

anaphase 2

Question 10

how are chromosomes stabilised, what are the specific group of stabilising molecules called?

Answer 10

meiosis specific cohesins (Rec-8 cohesins)

Question 11

at which pre meiotic phase are cohesins loaded onto the chromosome?

Answer 11

S phase

Question 12

after being loaded onto chromosomes, are cohesive cohesins replenished?

Answer 12

no

Question 13

after the bivalent chromosomes are stabilised by cohesins, what occurs?

Answer 13

monopolar attachment of sister centromeres

Question 14

what is the name of the proteins which protect cohesin (Rec-8) at the centromere? what do they recruit for this?

Answer 14

shugoshin proteins (Sgo1 and 2), recruit phosphatase PP2A

Question 15

Which shugoshin protein recruits phosphatase, dephosphorylating Rec-8 so separase doesn’t cleave it?

Answer 15

Sgo2

Question 16

if separase is not cleaved by phosphatase, what will happen to the chromosomes?

Answer 16

chromosomes will not align = aneuploidy

Question 17

centromeric cohesin enables the bipolar attachment of sister chromatids and their accurate segregation during which meotic division?

Answer 17

second

Question 18

in which phase of meiosis is centromeric rec-8 deprotected and cleaved by separase? what does this allow?

Answer 18

anaphase 2, allows sister chromatids to separate

Question 19

during which phase of meiosis does Sgo2 protect Rec-8 at centromeres?

Answer 19

anaphase 1