W10 L3 evolutionary conflict

Question 1

What does evolutionary conflict mean

Answer 1

-Conflict occur when gene have different patterns of transmission but interact directly or indirectly in the organism
-obvious example is gens of pathogen and gene of host
-endless cycle of damage and damage control lead to evolution arm race

Question 2

consequence of evolutionary conflict

Answer 2

-affect evolution of gene , genome, cell and gene regulation
-constrain evolution
-sex determination
-population density
-direct impact on biodiversity
- influence behavior

Question 3

the consequence of arm race

Answer 3

-lead to lots of adaptation
-can also lead to serious constraint on adaptation and the “red queen”

Question 4

Evolutionary conflict type

Answer 4

-interspecific: host/ parasite, predator and pre
-intraspecific:
Intragenomic: cytoplasmic vs nuclear gene
-inter genomic: sexual antagonistic alleles, male female behavior

Question 5

What are selfish genes

Answer 5

Gene that subvert Mendelian pattern of inheritance to increase in frequency in the next generation
-hence the name
-selfish genetic element are present in all living organism

Question 6

Example of selfish genetic element

Answer 6

-transposable element (autonomous replicator)
-segregation disorder (driving chromosome)
-post-segregation disorder (maternal effect lethal, endosymbiont)
-persist due to their selfish nature

Question 7

SGE and Intra genomic conflict

Answer 7

-genomic tension
-counter selection: silencing and inactivation
-adaptation and coutner adaptation
-genomic tug of war
-unresovalble

Question 8

When does genetic conflict occur and effect of SGE on host

Answer 8

• When different components of the genetic system are selected in the opposite direction
• SGEs are elements that enhance their own transmission relative to their host genome
• Can be detrimental to their host

Question 9

Segregation distorted: meiosis drive

Answer 9

• Segregation distorter genes cheats during meiosis or gametogenesis and are present in more than a half of the functional gametes
• Often found in inverted regions of chromosomes, and hence protected from recombination
  -exp: t haplotype in mouse, S.D in melanogaster

Question 10

meiosis drive

Answer 10

-segregation distorted that are present in sexual chromosome (as the Y chromosome in human s) are called sex ratio distorter
-most well studied are sex ration in D.simulan and pseudoobscura

Question 11

Sex linked meiotic drive are

Answer 11

-common
-associated with sex ratio distortion
- strong selection for suppression of drive to restore sex ratio
- drive only detected in population crosses
- risk of population extinction due to lack of one sex

Question 12

inherited endosymbionts

Answer 12

-asymmetric (uni parental ) inheritance
-commonly in cytoplasm of eggs
-male evolutionary dead end (no cytoplasm)

Question 13

Wolbachia diversity and abundance

Answer 13

-infect 20% of insects, possible 75%
20-30% of terrestrial isopods are infected
-wide spread in mite and spider

Question 14

cause of sex ratio skewing in wolbachia

Answer 14

• Because the bacteria have zero fitness in males, there is strong selection pressure to bias the sex ratio towards females
  = males represent an evolutionary dead end

Question 15

Way wolbachia cause genetic conflict

Answer 15

-parthenogenesis induction
-feminization
-Cytoplamic incompatibility
-male killing
-different strain of wolbachia can cause speciation

Question 16

Does only wolbachia lead to speciation?

Answer 16

• gut bacteria in an organism can also lead to incompatibility and speciation

Question 17

Genetic conflict and sex determination

Answer 17

• Sex determination systems are very diverse and rapidly evolve
• When components of the sex determination system are selected in opposite directions
  *lead to Genes have different inheritance patterns (e.g. cytoplasmic, autosomal, and sex chromosomal)
• Genes have different sites of expression (maternal, paternal, and zygotic)

Question 18

Type of genetic conflict in sex determination

Answer 18

• Intra-genomic conflict (e.g. meiotic drive sex chromosome and autosomes)
• Conflicts between parents and offspring over offspring sex
• Conflict between masculanizing and feminizing genes

Question 19

Cyto-Nuclear Conflict

Answer 19

• Conflict between cytoplasmic and nuclear genes over sex determination
• Nuclear genes r F=0.5 , r M=0.5
• Cytoplasmic genes (mitochondria, some bacterial endosymbionts) r F=1, r M=0
• Enhance their own transmission if they manipulate their host to produce a more female biased sex ratio.
  Males are a dead end. Can result in extinction
• Promote suppression to restore sex ratio - new sex determination system

Question 20

SGEs and sex chromosomes

Answer 20

• Sex chromosomes are magnets for SGEs
• Reduced recombination between X and Y favour accumulation (Hurst & Pomiankowski 1991)
• Suppressors favoured on different genomic regions = conflict over sex chromosome transmission

Question 21

SGEs promote sex determination turnover

Answer 21

• Birth of a W sex chromosome by horizontal transfer of Wolbachia genome
  -ZZ male, ZW female after infection become ZZ and ZZ+wo
  -wolbachia nucler intergration lead to creation of new sex chromosome W for female

Question 22

Conflict result in unusual sex determination

Answer 22

• Conflict between SGEs and their suppressors leads Multiple sex chromosomes in rodents

Question 23

Sex-ratio conflicts in social insects

Answer 23

• Mother queen: equally related to sons and daughters (rF =0.5, rM =0.5) > Wants to invest equally in both sexes
• Workers: 3 x more related to sisters than to brothers (rF =0.75, rM =0.25) > Prefer 3:1 F:M sex-ratio
• Parent-offspring conflict !

Question 24

Fratricide in ants

Answer 24

Wood ant Formica exsecta: facultative sex-ratio biasing. Some colonies with single mated queen, others with double mated queen. Workers only eat their brothers in colonies headed by a single mated queen

Question 25

Parent-Offspring Conflict cause

Answer 25

* Parents and offspring are not genetically identical * You are always more related to yourself than to your siblings * Parents are equally related to all their children * So, there is conflict due to differences in resource allocation desire and actually receive

Question 26

Pre-Natal Conflict (Haig 1993)

Answer 26

* Investment during pregnancy reduced ability to invest in current/future children * Fetus ʻdesiresʼ more investment than motherʼs optimum * Fetal genes try to increase nutrient transfer, maternal genes try and resists, leads to arms race

Question 27

conflicts of interest in mating system

Answer 27

-In monogamous species mother and father interests coincides * If polyandrous, there is conflict over mother and father allocation * Mother wants even allocation to this and future offspring * Father wants relatively more allocation to this offspring at the expense of other due to paternity uncertainty

Question 28

Genomic Imprinting

Answer 28

* Gene effect are absent/present depending which parent it is inherited from * Maternally inherited copy of genes has different effect than paternally inherited copy * Gene is turned on or turned off during spermatogenesis * Likely caused by methylation

Question 29

Genomic Imprinting example

Answer 29

* Paternally imprinted genes code for nutrient extraction * Placenta appears to be coded for by paternal genome

Question 30

Genomic Imprinting, which animal have this

Answer 30

* In mice, there is a paternally imprinted gene * When this gene is removed from mice, this slows growth in offspring * Possible human analog: syndrome of missing chromosome 7, causes abnormal fetal growth * Effects of arms race may include gestational diabetes and hypertension (include. pre-eclampsia)

Question 31

The ultimate parent-offspring conflict consequences

Answer 31

* Potential killing or abandoning offspring * Only favoured when there are better future opportunities * More likely when young as reproductive opportunities declines with age * Predict abandonment and infanticide should decline with mother’s age

Question 32

What does parental investment depend on

Answer 32

* Relatedness between parent and offspring * Ability of offspring to translate investment into reproduction * Alternatives: other possible uses of resources allocated to a given offspring