Lecture 33

Question 1

Measuring variation in a population

Answer 1

• Visible differences in phenotype
• Chromosome differences (eg. length of long arm of Y)
• immunological markers (eg. blood groups)
• protein gel electrophoresis (eg. esterases in Dros)
• SSLPs (simple sequence length polymorphisms) or VNTR (variable number of tandem repeats)
• STR or (short tandem repeats)
• Single nucleotide polymorphisms (SNP)

Question 2

Molecular level variation

Answer 2

Minisatellites (15-100b eg. tandem repeat of 18 bases) VNTR
Microstatellites (short tandem repeats 2-9 bases
Single nucleotide polymorphisms (1 base) - can be detected by DNA sequencing, restriction cutting sites
(Varies between people so can be used to find variations in people)

Question 3

Multilocus probe

Single locus probe

Answer 3

Multilocus probe is found in more than one location (minisatellites)
Single is

Question 4

Used to…

Answer 4

parentage, crime, victim indent, animal indent, conservation biology

Question 5

To calculate allele frequency when heterozygote can be recognised

Answer 5

homo x2 + hetero x1

over (total) x2

Question 6

When complete dominance and heterozygote same pheno as homozygote

Answer 6

assume hardy-weinberg equilibrium which is that genotypes are in proportions if p=f(A) allele q=f(a) allele. p^2=f(AA), 2pq=f(Aa), q^2=f(aa)

Question 7

The Hardy-Weinberg Equilibrium

Answer 7

p^2+2pq+q^2 = 1

Question 8

Assumption of H-W Equil

Answer 8

1) Random mating
2) no migration (no gene flow)
3) no selection acting (everyone equally likely to have same amount of babies
4) no mutation
5) infinite population size

Question 9

When not HW

Answer 9

and trait is autosomal, is can be restored in one generation of random mating NOT so for an x-linked trait

Question 10

Selection not controlled for

Answer 10

May sig. alter allele frequencies or hold them constant
Relative fitness (w) - 0 if condition is lethal or no offspring produced
1 for genotype leaving most offspring
Selection coefficient is s
relative fitness = 1 - s if s=1 all dead (as selection increases fitness decreases)

Question 11

Selection can be changed by the envirionment

Answer 11

climate, pollution, predators, disease, insecticide

Question 12

Stabilizing selection

Answer 12

selection against the extremes in the phenotype

Question 13

Disruptive selection

Answer 13

selection against the intermediate phenotypes

Question 14

Directional selection

Answer 14

selection for one phenotype from the end of the phenotypic range

Question 15

Mutation

Answer 15

• very little effect to allele frequencies on its own
• source of all new alleles
• w/ selection can be significant

Question 16

Migration (gene flow)

Answer 16

may be significant depending on m and difference between x and p (&p = m(x-p)

Question 17

Non-random mating

Answer 17

• inbreeding, consanguinity, self-fertilisation –> mating between related indiv. (genetic relationship, alters genotypic ratios by increasing homozygosity)
• Assortative mating (AM)
• -> select individuals like themselves (positive AM)
• -> select indivduals unlike themselves (negative AM, increase heterozygosity)

Question 18

Population size

Answer 18

may be significant

• random changes in allele frequencies due to sampling error
• occurs in all populations but effect pronounced in small populations

Question 19

Founder effect

Answer 19

small group from a larger population settle in a new location

Question 20

Bottleneck

Answer 20

population goes through a severe reduction and only a few members survive to produce next generations

Question 21

Speciation

Answer 21

separation of gene pools

• Allopatric (physical barrier separates gene pools)
• Sympatric (separation of gene pools occurs in the same area)

Question 22

Reproductive Isolation

Answer 22

Prezygotic mechanisms: prevent fertilisaiton and zygote formation
1) habitat - geographic or ecological isolation
2) seasonal or temporal
3) ethological/behavioural (courtship)
4) mechanical
5) physiological (gametes make it to female but do not survive)
Post-zygotic mechanisms
1) hybrid inviability or breakdown
2) Developmental hybrid sterility
3) F^2 breakdown