Lecture 7: intragenomic conflict

Question 1

groups of cooperators are known well at different levels:

Answer 1

• Genes in a genome (i.e. chromosome of Drosophila melanogaster)
• cells in a multicellular organism
• bees in a hive (honey bee queen and workers)

Question 2

Conflict: Tennyson

Answer 2

• Tennyson 1850 ‘Nature, red in tooth and claw’
• -Animals competing over food
• • male vs male conflicts
• • plants competing for light or water

Question 3

Richard dawkins

Answer 3

1976 ‘the selfish gene’

Question 4

‘selfish gene’ what does this mean

Answer 4

• when one organism helps another (parent & offspring) the organism could be described as being altruistic (donor help recipient at a cost)
• but this behaviour to the gene is considered to be selfish (helping copy of their own genes in offspring)
• -level at organism = altruistic
• -level at gene = selfish

Question 5

an organism whose altruistic behaviour is caused by

Answer 5

selfish genes

Question 6

genes that help other genes at the detriment to themselves what would happen

Answer 6

they would be selected against & eliminated from gene pool

Question 7

Are selfish genes in conflict?

Answer 7

parental genes at different autosomal loci typically have same probability to be passed on to offspring
-so no conflict among genes at different loci concerning how much to help the offspring

Question 8

strategies for genes to follow to increase frequency in next generations:

Answer 8

1) build a better organism thereby enhancing total reproduction of bearer
2) manipulate host organisms reproduction to have a greater chance of being passed on to offspring (ultraselfish genes)

Question 9

transposons

Answer 9

spread along genome making copies of themselves

Question 10

ultraselfish genes:

Answer 10

• can be selected for even when they don’t help organism

- they can in fact harm the organism so that its total reproduction is diminished

Question 11

ultraselfish gene at work: cytoplasmic male sterility

Answer 11

• maize plant is male sterile, no pollen on male tassel
• introgenomic conflict occurs between nuclear and cytoplasmic genes
• –> HHHHH

Question 12

offspring has nuclear genes from ____, mitochondrial from __

Answer 12

mother and father,

mother only

–so males pass on no cytoplasmic genes

Question 13

cytoplasmic male sterility: in many angiosperms

Answer 13

don’t produce pollen, so invest more in producing eggs

• functions as female only
• pollen from other plants then fertilise eggs to produce offspring
• -so if you were a mitochondrial gene you’d rather be in CMS

Question 14

how could CMS evolve?

Answer 14

only has to produce a little extra female function in order to evolve
-as M are a dead end for mitochondrial genes in angiosperms

Question 15

nuclear “restorer” genes

Answer 15

restore male functions in CMS
-conflict between cytoplasmic and nuclear genes –> with nuclear genes counteracting male sterility caused by cytoplasmic genes

Question 16

conflict between nuclear genes at same loci: conflict occurs due to

Answer 16

meiosis

Question 17

Females & meiosis conflict

Answer 17

meiosis results in egg & 3 polar bodies

-incentive for a gene to manipulate meiosis in females to increase its chance of being in egg rather than polar body

Question 18

males & meiosis conflict

Answer 18

meiosis produces 4 or more sperm, so each allele ends up in a gamete

• conflict due to sperm competition
• incentive for allele to harm any sperm not containing that allele so it has fewer competitors

Question 19

meiotic drive / segregation distortion =

Answer 19

unequal transmission of alternative alleles to offspring

Question 20

segregation gene in drosophila

Answer 20

Segregation distorter (SD) 
- SD prevents the rival sperm from being made

Question 21

segregation distorter gene in mouse

Answer 21

• t-locus (t gene)
• makes rival wild type sperm less competitive by deactivating them in the female reproduction tract
• knocks out wild type sperm after insemination once in female reproductive tract

Question 22

segregation distorters on sex chromosome distorts

Answer 22

sex ratio

Question 23

sex ratio distortion: an x-linked distorter cases a ____ biased sex ratio in the offspring of the male bearing it

Answer 23

female

Question 24

meiotic drivers (or segregation distorters ) are more easily detected if they affect

Answer 24

the sex ratio

Question 25

effect of mating system on distortion: monogamy

Answer 25

potential advantage from distortion can be great

Question 26

effect of mating system on distortion: polyandry

Answer 26

advantage from distortion decreases as more sperm from multiple males to compete with distortion

Question 27

effect of mating system on distortion: female mated to one male, male does not carry distorter gene

Answer 27

all sperm viable

Question 28

effect of mating system on distortion: female mated w one male that carries distorter gene

Answer 28

sperm not carrying distorter gene are knocked out. Distorter sperm fertilise 100% of the eggs, not 50%

Question 29

female mated to two males. 1 male carries distorter gene

Answer 29

• wild type sperm from distorter carrying male are knocked out
• other males sperm are unaffected
• distorter fertilises 33%
• -> reduces further with each mating
• female can poss dump distorter sperm so non-carrying male will be most successful –> cryptic female choice

Question 30

Female _____ distorter sperm so distorter male fertilises 0 eggs

Answer 30

recognises and dumps