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Flashcards in Meotic drive Deck (61)
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1

What kind of division is meiosis?

A reduction division

2

What is a reduction division?

Transformation of the diploid state to the haploid state

3

What does meiosis produce?

The gametes

4

How many daughter cells does meiosis produce?

4

5

What is meiotic drive?

When a selfish genetic element distorts meiosis to enhance its own transmission

6

Is meiotic drive at cost to the host?

Yes

7

Does meiotic drive distort the sex ratio of the progeny?

Sometimes

8

Simple meiotic drive occurs in males. How does it work? What type of drive is it?

There are two loci involved, Killer (toxin) and Resistant (antitoxin).
Sperm with the Killer locus kills other sperm but are themselves resistant to the toxin, and so the meiotic driver is proliferated.

9

What is necessary for simple/male meiotic drive to work?

Tight linkage between the Killer and Resistant alleles so that they are not broken up by recombination.

10

The production of sperm and eggs differ. When a primary spermatocyte divides, what does it produce?

Two secondary spermatocytes

11

The production of sperm and eggs differ. When a primary oocyte divides, what does it produce?

One secondary oocyte and one polar body (which divides into 2)

12

The production of sperm and eggs differ. When a secondary spermatocyte divides, what does it produce?

Two spermatids

13

The production of sperm and eggs differ. When a secondary oocyte divides, what does it produce?

One ootid and one polar body

14

So overall, what is produced by the a) primary spermatocyte and b) primary oocyte in meiosis?

a) 4 sperm cells
b) 1 ovum and 3 polar bodies

15

In oogenesis, at what stage do homologous chromosomes separate?

Transition from primary to secondary oocyte

16

In oogenesis, at what stage do sister chromatids separate?

Secondary oocyte to ootid

17

What does the ootid give rise to?

The ovum (egg)

18

What holds the sister chromatids together?

The centromere

19

In female meiosis, what is the selfish element? What does it do?

The centromere, it never ends up in the polar body when the secondary oocyte divides

20

One study found evidence for female meiosis.

a) Who did it?
b) What year?
c) Which organisms did they study?

a) Fishman and Saunders
b) 2008
c) Monkey flowers, M. guttatus and M. nastus

21

In Fishman and Saunders' 2008 experiment on monkey flowers, what happened?

In hydridisation experiments M. guttatus always showed 100% segregation, i.e. it never ended up in the polar body, due to a duplication of centromeric DNA

22

Suppressors have evolved to counter meiotic drive. What are the two types?

Linked and non-linked

23

What are meiotic drivers often referred to as?

Segregation distorters

24

Who worked on D. melanogaster, what year?

Larracuente and Presgraves, 2012

25

Larracuente and Presgraves (2012):
D. melanogaster has a segregation distorter involving two loci. What are they?

Sd = a toxin
Rsp = a responder/antitoxin

26

Larracuente and Presgraves (2012):
What is Sd?

A partial duplication of RanGAP. Sd-RanGAP fails to leave the nucleus and accumulates as a toxin.

27

Larracuente and Presgraves (2012):
There are two alleles of Rsp. What are they?

Rsp-i, provides immunity to Sd
Rsp-s, sensitive to Sd

28

Larracuente and Presgraves (2012):
What is the wildtype condition?

No Sd and Rsp-s

29

Larracuente and Presgraves (2012):
What is the mutant/selfish condition?

Sd and Rsp-i, immune to own toxin

30

Larracuente and Presgraves (2012):
Why is there low recombination between the Sd and Rsp loci? Give 3 reasons.

1. Genes are either side of the centromere, do not recombine
2. Lots of local inversions
3. Recombination unfavoured as produces 'suicide' and 'immune' chromosomes