Microevolution

Question 1

What makes evolution possible?

Answer 1

genetic variation

Question 2

Which processes produce variation in gene pools?

Answer 2

mutation and sexual recombination

Question 3

What is the difference between synonymous and nonsynonymous mutations?

Answer 3

Synonymous mutations don’t change the encoded amino acid, while nonsynonymous mutations changes the nucleotides that change amino acids.

Question 4

How strong is mutations as an evolutionary force?

Answer 4

Point mutation rates are generally low, making mutation a WEAK evolutionary force

Question 5

Are mutations only harmful?

Answer 5

Chromosomal mutations that delete, disrupt, or rearrange many loci are typically harmful, but when genes are left intact they may be neutral or benefitial

Question 6

What are some variation in the rates of mutation?

Answer 6

Sex- sperm has 5x mutations than female eggs
Generation time- single-celled organisms and viruses have many more generations per unit of time than larger ones
Environment- can increase the mutation rate
Stress- high stress leads to adaptive mutations

Question 6

What are some characteristics of mutations?

Answer 6

Common on a per gamete basis, but rare per gene
Many mutations with phenotypic effects are deleterious (bad) and recessive (hidden)

Question 7

What are two principal ways to not have random mating?

Answer 7

Assortative mating- like genotypes mate with each other, or avoid each other
Inbreeding- mating among individuals than are more closely related than those drawn by change from the population

Question 8

What does positive assortative mating do?

Answer 8

Decreases heterozygosity for the gene(s) affecting the trait
Heterozygotes decrease if similar genotypes are pairing, but only for the loci affecting the trait

Question 9

What does negative assortative mating do?

Answer 9

Increases heterozygosity for the gene(s) affecting the trait
Heterozygotes increase if dissimilar genotypes are pairing

Question 10

How does inbreeding change genotype frequencies?

Answer 10

Increases the proportion of homozygotes and reduces the proportion of heterozygotes across the entire genome.

Question 11

What is selfing?

Answer 11

Most extreme type of inbreeding, has effects like positive assortative mating, but across the whole genome

Question 12

What are the evolutionary consequences of non-random mating?

Answer 12

• Inbreeding results in genome-wide loss of heterozygosity (loss of diversity)
• Inbreeding and assortative mating only affect genotype frequencies (not allele ones) so their effects may be temporary
• Inbreeding reduces fitness by generating offspring homozygous for deleterious alleles (inbreeding depression)

Question 13

What did Sewall Wright contribute?

Answer 13

One of the scientists that contributed to the Modern Synthesis
Inbreeding
Genetic drift

Question 14

What is genetic drift?

Answer 14

*one of the basic mechanisms of evolution
*the evolutionary equivalent of a sampling error in the production of offspring of genotypes from the parental gene pool that results in random changes in allele frequencies
*eventually can lead to a species to be fixated or extinct

Question 15

What is the effect of genetic drift on smaller populations?

Answer 15

The impact of genetic drift is stronger on smaller populations
Leaves the smaller populations to be less genetically diverse

Question 16

What are long terms patterns of genetic drift that are sensitive to periods of small population time?

Answer 16

Population bottleneck: when a population goes through a period of unusually small population size
Founder effect: when a population goes through this period of unusually small population size at a time when it arrives to a new, uncolonized area

Question 17

Founder Effect

Answer 17

When a new colony is started by a few members of the original population, the small population size of the colony means that it may have a reduced genetic variation from the original population

Question 18

Population Bottlenecks

Answer 18

events in which a population’s size is greatly reduced (the asteroids killing a lot of dinosaurs).
Leads to genetic drift having a major effect on the population because allele frequencies in the population are likely to change just by random chance

Question 19

What is gene flow?

Answer 19

the transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes, can also change allele frequencies
ex: Duffy antigen that had alleles be popular in three different regions

Question 20

How is there chance in allele frequency due to gene flow?

Answer 20

Within a population, it can introduce alleles, increasing its genetic variation
Make distant populations genetically similar to one another, hence reducing the chance of divergence