Dynamics of Human Populations Flashcards
Gene flow vs genetic drift
Gene flow is the transmission of genes across populations, while genetic drift is the changing of allele frequencies in small groups, which allows alleles to vanish, this is the key difference.
Gene flow increases genetic diversity.
Genetic drift decreases genetic diversity.
Genetic drift: in a small population allele frequency tends to drift, while in a large population alles are stable.
Which one of hte following population phenomena decreases a genetic isolate’s genetic diversity?
A. Genetic drift
B. Gene flow
C. Mutation
D. Population admixture
E. Random mating
A. Genetic drift
For an autosomal dominant disorder with a stable incidence and a fitness of 0.6, what is proportion of new cases due to new spontaneous mutation?
40%
The observed heterozygous frequency being higher than expected from Hardy-Weinberg calculation supports which one of the following?
A. Assortive mating
B. Balanced polymorphism
C. Founder effect
D. Recurrent mutations
E. The Malaria Hypothesis
B. Balanced polymorphism
A sobering example of balanced polymorphism comes from the study of
sickle cell disease (SCD). SCD is an autosomal recessive disorder that is
associated with significant morbidity and mortality, and markedly reduced fitness. In sub-Saharan Africa, where malaria is endemic, individuals homozygous for wild-type hemoglobin have a high susceptibility to the infection, whereas heterozygotes (Aa) have greater resistance to the infection. This heterozygote advantage gives a positive selective force for the sickle allele that is balanced against the negative selective force exerted on homozygous wild-type and sickle cell disease individuals. Over generations, a very delicate balance is attained that yields a high but stable frequency for sickle cell disease in many part of Sub-Saharan Africa. This concept of balanced polymorphism has been used to explain the high and stable frequencies of other autosomal recessive disorders when it was found that affected populations were not in HWE, and have much higher heterozygote frequencies than is expected.
A small number of individuals from one population migrate into another population and reproduce there. This phenomenon is called…
gene flow
The high incidence of Tay-Sachsdisease among Cajuns is an example of….
Founder effect
Which one of hte following events does not increase genetic diversity in a population?
A. Gene flow
B. Genetic drift
C. Mutations
D. Population admixture
B. Genetic drift
In the year 2500, 10 males and 10 females are randomly selected to start a new human colony on Mars. After 20 generations, it is found that the percentage of homozygotes at a large number of loci among the colonists is much higher than the percentage of homozygotes among the original founders. This is most likely due to
A. genetic drift
B. inbreeding (except incest)
C. monozygoticc twinning
D. natural selection
E. spontaneous new mutations
A. genetic drift
