GN 1.1.3 Flashcards Preview

Genetics and Neoplasia > GN 1.1.3 > Flashcards

Flashcards in GN 1.1.3 Deck (38):
1

What are the goals of meiosis?

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

2

What are homologous chromosomes?

Chromosomes that differ in parental origin

3

What are sister chromatids?

Two copies of a single chromosome produced by DNA replication

4

What is a bivalent?

Structure formed from association of homologous chromosomes.

5

What are the characteristics of meiosis 1?

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

6

What are the characteristics of meiosis 2?

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

7

What is the key feature of homologous chromosome pairing?

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

8

What is the synaptonemal complex?

It acts as the glue that holds together homologous chromosomes

9

What is homologous recombination?

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

10

What is happening in the leptotene stage of prophase 1?

Chromosome condensation, Bouquet formation, and double stranded breaks occur

11

What is happening at the zygotene stage of prophases 1?

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

12

What is happening at the pachytene stage of prophase 1?

Completion of desynapsis and maturation of meiotic recombination sites into crossovers

13

What is happening at the diplotene stage of prophase 1?

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

14

What are chiasmata?

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

15

Abnormal crossovers are what?

Sub optimally placed exchanges are associates with non-disjunction

16

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

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

17

Most aneuploidies have a high or low mortality rate?

HIGH

18

When does meiosis begin in males vs females?

Males starts at puberty and females starts at fetal development

19

What are the characteristics of meiosis in females?

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

20

For men each cell that enters meiosis produces what?

4 haploid sperm

21

For females each cell that enters meiosis produces what?

A single mature egg and 2 polar bodies

22

Most meiotic errors are?

Maternal in origin

23

Do eggs or sperm have more stringent checkpoints?

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

24

As female birthing age increases the rate of trisomies?

Increases as well

25

What is non-disjunction?

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

26

Why are cohesions a likely target for aneuploidy?

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

27

How does BPA affect meiosis?

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

28

Homologous chromosome pairing occurs in what phase?

Prophase 1

29

Synaptonemal complex formation occurs in what phase?

Prophase 1

30

Recombination and crossing over occurs in what phase?

Prophase 1

31

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

Synaptonemal Complex

32

What is the order of the substages of Prophase 1?

Leptotene, Zygotene, Pachytene and diplotene

33

When is cohesion established?

Pre-meiotic S phase

34

Chromosome condensation, Bouquet formation, and double stranded breaks occur

Leptotene

35

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

zygotene

36

Completion of synapsis and maturation of meiotic recombination sites into crossovers

Pachytene

37

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

Diplotene

38

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

Aneuploidy