Genetic Drift and Gene Flow

Question 1

Gene flow

Answer 1

Process by which populations of a species exchange alleles (individuals)
- introduces new variation into a population
- but decreases the difference between populations

Question 2

Gene flow is greater when populations are…

Answer 2

Closer to each other and then decreases with increasing distance

Question 3

What primarily impacts patterns of genetic differentiation among ethnolinguistic groups?

Answer 3

Geography

Question 4

Genetic drift

Answer 4

A random change in allele frequency
- can occur as a result of sampling error

Question 5

Sampling error

Answer 5

When a sample differs from the population it was drawn from

Question 6

Sampling error can compound over trials…

Answer 6

leading to fixation

Question 7

Fixation

Answer 7

The frequency of an allele is driven to one or zero
- drift operating alone will ALWAYS lead to fixation (given enough time)

Question 8

The effect of genetic drift depends on what?

Answer 8

Population size
- fixation/loss occurs more often in small populations
- rate of genetic drift faster in smaller populations

Question 9

Cranial shape differs among human populations and some of this shape difference is due to natural selection, but the majority appears to be due to what?

Answer 9

Shared population history
- shaped by the evolutionary force of genetic drift, with some contribution of gene flow

Question 10

Founder’s effect (drift)

Answer 10

New population formed by a small number of “founding” individuals
- founder population unlikely to accurately represent genetic variation in original population

Because founding population was small…
- drift quickly increases the frequency of rare variants

Question 11

Endogamy: a human behavior that affects gene flow
How culture affects biology

Answer 11

• reproduction (marriage) with other individuals within the group
• affects gene flow
• Amish populations will look genetically similar to each other not to nearby populations
• will also have the result of increasing the frequency of homozygotes

Question 12

Why does endogamy increasing the frequency of homozygous important?

Answer 12

Ellis-Van Creveld syndrome is an autosomal recessive disorder that is typically very rare, but occurs more commonly in Amish populations since they like to reproduce with their kind

Question 13

Why is it important to understand the forces of evolution?

Answer 13

Helps scientists and medical professionals understand the causes of disease and special challenges facing specific populations
- also helps us understand patterns of diversity

Question 14

Bottleneck (drift)

Answer 14

Former population is huge and variable
Bottleneck severely reduces population size and genetic diversity
New population grows but with less genetic diversity than former population since not all variation survived