GN 1.1.3

Question 1

What are the goals of meiosis?

Answer 1

creation of haploid gametes that upon fertilization will created diploid zygotes and generation of genetic diversity

Question 2

What are homologous chromosomes?

Answer 2

Chromosomes that differ in parental origin

Question 3

What are sister chromatids?

Answer 3

Two copies of a single chromosome produced by DNA replication

Question 4

What is a bivalent?

Answer 4

Structure formed from association of homologous chromosomes.

Question 5

What are the characteristics of meiosis 1?

Answer 5

Reductional division is which homologous chromosomes separate (2N to N).

Question 6

What are the characteristics of meiosis 2?

Answer 6

Equatorial division in which sister chromatids are separated (2C to C) (N to N)

Question 7

What is the key feature of homologous chromosome pairing?

Answer 7

Attachment of clustering telomeres at the nuclear envelope leading to rapid chromosome movement

Question 8

What is the synaptonemal complex?

Answer 8

It acts as the glue that holds together homologous chromosomes

Question 9

What is homologous recombination?

Answer 9

Programmed dsDNA breaks at “hot spots” leading to invasion into the chromatid by the homologous chromosome. Failure of a chromosome pair to undergo atleast one crossover event can lead to aneuploidy

Question 10

What is happening in the leptotene stage of prophase 1?

Answer 10

Chromosome condensation, Bouquet formation, and double stranded breaks occur

Question 11

What is happening at the zygotene stage of prophases 1?

Answer 11

pairing extends, AE matures into LE, and the synapsis begins

Question 12

What is happening at the pachytene stage of prophase 1?

Answer 12

Completion of desynapsis and maturation of meiotic recombination sites into crossovers

Question 13

What is happening at the diplotene stage of prophase 1?

Answer 13

Chromosomes undergo synapsis, homologues are held together by crossovers, and further condensation occurs

Question 14

What are chiasmata?

Answer 14

Physical manifestations of genetic recombination that tethers homologous chromosomes; there are about 1-2 per homologous chromosome pair.

Question 15

Abnormal crossovers are what?

Answer 15

Sub optimally placed exchanges are associates with non-disjunction

Question 16

What is a cohesion and when is it added to the homologous chromosome?

Answer 16

Multi-protein complex that stabilizes the physical linkages that form as a result of homologous recombination added during development S phase.

Question 17

Most aneuploidies have a high or low mortality rate?

Answer 17

HIGH

Question 18

When does meiosis begin in males vs females?

Answer 18

Males starts at puberty and females starts at fetal development

Question 19

What are the characteristics of meiosis in females?

Answer 19

Initiatied at 11-12 weeks of gestation in a fixed and finite pool
By birth all oocytes are arrested in the diplotene stage of meiosis I
Meiosis I is completed at ovulation and meiosis II is completed at fertilization

Question 20

For men each cell that enters meiosis produces what?

Answer 20

4 haploid sperm

Question 21

For females each cell that enters meiosis produces what?

Answer 21

A single mature egg and 2 polar bodies

Question 22

Most meiotic errors are?

Answer 22

Maternal in origin

Question 23

Do eggs or sperm have more stringent checkpoints?

Answer 23

Checkpoint mechanisms are more stringent in males, oogenesis is more robust but it can lead to more meiotic errors

Question 24

As female birthing age increases the rate of trisomies?

Answer 24

Increases as well

Question 25

What is non-disjunction?

Answer 25

When there is failure to separate and both sets of chromosomes go to a single cell

Question 26

Why are cohesions a likely target for aneuploidy?

Answer 26

They are loaded on to chromosomes during fetal S phase. Which is required during chromosome segregation. The problem is that you are using older proteins the older you get

Question 27

How does BPA affect meiosis?

Answer 27

BPA is weakly estrogenic, and it can lead to meiotic aneuploidy

Question 28

Homologous chromosome pairing occurs in what phase?

Answer 28

Prophase 1

Question 29

Synaptonemal complex formation occurs in what phase?

Answer 29

Prophase 1

Question 30

Recombination and crossing over occurs in what phase?

Answer 30

Prophase 1

Question 31

This is referred to as the tripartite structure that serves as the molecular glue holding together homologous chromosomes

Answer 31

Synaptonemal Complex

Question 32

What is the order of the substages of Prophase 1?

Answer 32

Leptotene, Zygotene, Pachytene and diplotene

Question 33

When is cohesion established?

Answer 33

Pre-meiotic S phase

Question 34

Chromosome condensation, Bouquet formation, and double stranded breaks occur

Answer 34

Leptotene

Question 35

pairing extends, AE matures into LE, and the synapsis begins

Answer 35

zygotene

Question 36

Completion of synapsis and maturation of meiotic recombination sites into crossovers

Answer 36

Pachytene

Question 37

Chromosomes undergo desynapsis, homologues are held together by crossovers, and further condensation occurs

Answer 37

Diplotene

Question 38

Failure of a chromosome pair to undergo atleast one crossover event can lead to?

Answer 38

Aneuploidy