Gene Pools and Changes in Allele Frequencies

Question 1

Define population.

Answer 1

A group of organisms of the same species living together.

Question 2

Define species.

Answer 2

A group of organisms that share similar characteristics and are able to interbreed to produce fertile offspring.

Question 3

Define geneticists.

Answer 3

Specialise in the study of inheritance and consider the characteristics that make up a population.

Question 4

Define gene pool.

Answer 4

The grouping of genotypes within the population and is the sum of all alleles.

Question 5

Define allele.

Answer 5

AN alternative form of a gene.

Question 6

Define allele frequency.

Answer 6

How often a particular allele occurs.

Question 7

What are the 5 methods variation in a population can be caused?

Answer 7

1. Random Assortment.
2. Crossing over.
3. Non-disjunction.
4. Random fertilisation.
5. Mutations.

Question 8

What is Random genetic drift?

Answer 8

Is a non-directional variation in allele frequency that occurs in small populations due to chance events. An allele that is rare in a large population can become frequent in a small population.

Question 9

What is the Bottleneck effect?

Answer 9

Occurs when a population is sharply reduced
.

Question 10

What is the Founder effect?

Answer 10

Occurs when small groups move away from its homeland.

Question 11

What can the founder effect cause?

Answer 11

1. A different allele frequency from the original population.
2. Decreased genetic variation.

Question 12

Describe an example of the Founder effect.

Answer 12

The incidence of Tay-Sachs disease in Ashkenazi Jews. Approximately 1 in 27 Ashkenazi Jews carry the altered allele compared to 1 in 3000 in non-Ashkenazi Jews. This group descended from a small group of individuals from central or eastern Europe. The group was isolated both geographically and through the custom of endogamy. This created the founder effect.

Question 13

Describe an example of the Bottleneck effect.

Answer 13

The bottleneck effect occurred when the typhoon reduced the population of Pingelap to 20 people. The survivors formed the founding population for current inhabitants. Among the survivors, a person was heterozygous for the recessive allele achromatopsia. The incidence of colour blindness on Pingelap is 5% compared to the rest of the world which is 0.0033%.

Question 14

How is random genetic drift different to natural seletion?

Answer 14

1. Occurs due to chance events.
2. There are no selection pressures that influence changes in allele frequency.
3. More likely to occur in smaller populations.