Definitions

Question 1

population

Answer 1

randomly mating group of individuals of the same species

Question 2

theory

Answer 2

set of principles, based on large body of expectations and observations accepted by scientists

Question 3

gene

Answer 3

physical entity transmitted from parent to offspring in reproduction that influences hereditary traits

Question 4

allele

Answer 4

different states of a gene

Question 5

locus (loci)

Answer 5

position of a gene / marker on a chromosome

Question 6

Hardy-Weinberg principle

Answer 6

model to predict genotype frequencies under ‘random’ mating in an ‘ideal’ population
With two alleles (A and B) the frequencies of genotypes AA, Ab and B B are p^2, 2pq and q^2
A population that is under hardy-weinberg equilibrium if there isn’t a significant difference between the genotype numbers observed than expected

Question 7

Non random mating?

Answer 7

assortative mating - (positive assortative mating) similar individuals mate more often than expected under random mating (reduction of heterozygotes)
disassortative mating - (negative assortative mating) dissimilar individuals mate more often than expected under random mating (increases heterozygotes)

Question 8

mutation (u)

Answer 8

• origin of new genetic variants (alleles)
• spontaneous heritable changes in genes
• weak force for changing allele frequencies
• generally increases diversity
• types: point mutations, insertions/deletions (indels), translocations, inversions
• mutation rate per locus (gene) = 1 x 10^-5
• mutations are often lost due to drift later

Question 9

migration

Answer 9

• movement of individuals with their alleles between (sub) populations
• new alleles in population because introduced from a different one
• generally increases diversity
• Migration of a few individuals per generation between populations prevents accumulation of high levels of differentiation between populations

Question 10

random genetic drift

Answer 10

• the random undirected changes in allele frequencies that occur by chance in all populations but particularly in small ones (eg. bottlenecks, small founder populations, endangered species)
• chance process
• generally lowers diversity
• fixation of alleles within populations (loss of rare allele)
• causes random differentiation between populations
• reduces variation within a population but increases variation between populations

Question 11

natural selection

Answer 11

driving force for adaptive evolution
differential survival and reproduction of individuals due to differences in phenotype.
1. in all organisms more offspring than can survive and reproduce
2. organisms differ in their ability to survive and reproduce, some of these differences due to the genotype
–> survival of the fittest
It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations.

Question 12

selection?

Answer 12

• balancing selection - heterozygote superiority
  maintains diversity in the population
• directional selection - leads to much lower frequency of allele that causes the low fitness in the genotype
• may lead to fixation or loss of an allele
• selection increases frequency of advantageous allele

Question 13

effective population size (Ne)

Answer 13

the size of the genetically ideal population which has the same rate of loss of heterozygosity as an actual , non-ideal, wild population

Question 14

metapopulation

Answer 14

collection of interacting populations (sub- pops) of the same species

• populations of many species occupy patches of high quality habitat and only use the in between land for movement
• no of isolated populations (lack of resources)
• low levels of variation within sub-pops
• as a whole either have same or higher variation than one large pop

Question 15

genomic conflict

Answer 15

genes that affect the same trait, but different pressures

- selfish cytoplasmic gene

Question 16

meiotic drivers

Answer 16

gene that distorts meiosis to produce gametes containing themselves over half the time (intragenomic)

• selfish drive elements gain trainsmission advantages through diverse genetic mechanisms
• wide range of consequences; extinction - changes in mating system
• can be natural / synthetic
• (t haplotype in mice)

Question 17

selfish cytoplasmic gene

Answer 17

gene located in an organelle, plasmid or intracellular parasite (endosymbiont) that modifies reproduction to cause its own increase at the expense of the cell / organism (intergenomic)

Question 18

Heteroplasmy

Answer 18

presence of more than one mitochondrial (or chloroplast) genome variant in an individual

Question 19

genotypic fitness

Answer 19

• usually expressed as relative fitness, w = 1 - S
• S = selection coefficient
• compared to a genotype with no selection (neutral)

Question 20

micro-satellite?

Answer 20

• a micro-satellite marker is a repetitive DNA sequence
• satellite DNA = tandemly repeated
• micro-satellites are highly polymorphic because the mutate more frequently
• short tandem repeats (microsatellites) evolve very fast
• mutations occur because polymerase makes mistakes during replication

Question 21

monomorphic?

Answer 21

1 allele is fixed in the population

Question 22

polymorphic?

Answer 22

both alleles are still present in the population

Question 23

Bottlenecks?

Answer 23

The population size is reduced dramatically by:
- regular events (seasonal variability in resources) - results in death of many in resource poor times
- irregular random events (storms / disease outbursts)
- sustained pressure (habitat destruction / human hunting)
EXAMPLE: Northern elephant seals have reduced genetic variation most likely due to being hunted. Hunting reduced their population size to as few as 20 individuals at the end if the 19th century

Question 24

Founder effect?

Answer 24

a new population is founded by a few individuals: 2 consequences:
1. loss of variation - an allele may be lost so the population may be genetically monomorphic
2. diversification by drift - in small pops, frequencies of alleles may drift from the parental population –> high frequencies of otherwise rare alleles
EXAMPLE: Amish population in Pennsylvania:
- closed pop origin from a small number of german immigrants (200)
- carry unusual concentrations of rare disorders (Ellis-van Creveld syndrome - causes dwarfism, polydactyly etc.)
- 50% have a hole in their heart
- traces back to Samuel King and wife came to area 1744 and mutated gene passed on to offspring

Question 25

Genetic variation - why is it important?

Answer 25

loss of genetic variation leads to:

• inbreeding depression - recessive lethals become homozygous
• inability to adapt to a changing environment / new diseases
• there is a high impact of low diversity on reproduction –> sperm abnormalities
• we can recover genetic variation using PCR

Question 26

Effective population size?

Answer 26

Ne (diploid) = 4 NmNf / (Nm + Nf)

• size of the ideal pop with same genetic variation as the real pop
• Ne is affected by the mating structure of the population (eg. harems)
• sex ratio will be skewed in dominance systems, Ne decreases rapidly as breeding ratio becomes biased to 1 sex

Question 27

Sociality and effective population size?

Answer 27

• eusociality = colonial animals (ants / bees)
• Ne of a eusocial insect with 1 queen and many drones is low compared with solitary insects
• hives are like small families
• eusocial insects are expected to have a smaller Ne than N

Question 28

Haplodiploidy?

Answer 28

• sex determining mechanism by which males develop from unfertilised eggs (males = haploid and produced by parthenogenesis)
• females are produced by fusion of eggs and sperm
• haplodiploidy means a lower Ne than in diploid species
• Ne = 9Nf x Nm / (2Nf + 4Nm)
• haplodiploid species have less genetic variation due to lower Ne
• eusocial haplodiploid insects also have lower genetic diversity than solitary insects
• there is a strong impact of mating systems on total genetic diversity

Question 29

multivariate analysis?

Answer 29

• principle component analysis (PCA)
• its hard to interpret multivariate data
• doesn’t test hypothesis but is ‘data exploration
• allows us to visualise and understand patterns in the data
• it calculates a reduced set of dummy variables that explains the variance in the data set
• it gives coefficients that allow you to calculate these dummy variables
• PCA is a technique that finds underlying variables (principle components) that best differentiate your data points
• its a regression with n variables, so n regression lines, so n dimensional
• you only count the factors that are above 1 eigen value

Question 30

evolutionary arms race?

Answer 30

• describes competition where each party evolves to stay alive
• RICHARD DAWKINS - “ arms race … a colourful way of talking about co-evolution, particularly between enemies. adaptations on one side call for adaptations on the other, and so on, escalating all the time” “the apparatus we see improves but the efficacy doesn’t as the other side gets better at the same time”
• Red Queen Hypothesis
• examples of arms races; sexual selection, parent-offspring conflict, predator-prey
• 2 principles:
  1. the one running for its life will have the upper hand than the one chasing its dinner
  2. evolutionary specialists do not win as they need to give up opportunities when specialising on others

Question 31

QTL mapping?

Answer 31

• the meeting of quantitative + traditional genetics
• Quantitative Trait Loci = genes that together determine a complex character
• generally 3-6 major genes and many minor
• Linkage Disequilibrium (LD) = association of a marker (genotype) and a phenotype
• genes / markers close together on a chromosome will be co-inherited more often together
• helps us see heritabilities in humans, determine medical issues, and in forensics
• QTLs are mapped by identifying which molecular markers correlate with an observed trait

Question 32

Asexual reproduction?

advantages and disadvantages

Answer 32

• efficient
• produces offspring identical to parent
• single celled orgs = division into daughter cells
• multicellular = bud of single cells
  advantage = production of many offspring and no mate required
  disadvantage = little genetic variation in pop only gained through mutation / migration
• risk of extinction due to disease

Question 33

sexual reproduction?

advantages and disadvantages

Answer 33

• produces genetically diverse offspring
• 2 haploid gametes fuse to form zygote
• sex didn’t evolve because of reproduction
• sex os complex, ineffective yet common
  advantage =
• recombination accelerates rate of evolution
• cleanse lineages of mutational damage
• recombination eliminates mutations at once (purge)
• creates genetic combinations that flourish when common ones suffer
  disadvantage =
• two-fold reproductive disadvantage (anisogomy - males = waste)
• allowing meiotic drivers and selfish cytoplasmic genes
• recombination destroys favourable gene combinations
• finding a mate = costly
• STD infections

Question 34

synthetic drivers?

Answer 34

• useful in disease transmitting insects
• CRISP - Cas9: biotechnological method to alter very specific DNA sequences - generates drivers / male killers
  example: gene to control malaria:
• release of insects carrying synthetic GM dominant lethal
• adding the gene drive would make the system self sustaining for a longer time

Question 35

uniparental vs biparental inheritance?

Answer 35

mt and cp = uni-parentally inherited
- resolves conflict among organelles but creates conflict between sexes
- causes male sterility - nuclear restorer (Rf) genes evolve in response (arms race)
nuclear chromosomes = bi-parentally

Question 36

gynodioecious ?

Answer 36

co-occurence of hermaphrodites and females (male steriles) in a pop