Gene Pools

Question 1

What is a Gene Pool?

Answer 1

A gene pool is a sum of all the alleles in a given population at a particular place at a particular time

Question 2

What is an Allele?

Answer 2

Alternate forms of a gene

Question 3

What is Gene Flow?

Answer 3

The transfer of alleles from one population to another through migration i.e. Europeans into Australia

Question 4

What is a species?

Answer 4

A group of individuals that share many characteristics and can interbreed under normal conditions to produce an offspring

Question 5

What are the sources of variation within gene pools?

Answer 5

• Random Genetic Drift
• Founders effect
• Migration
• Barriers to Gene Flow
• Genetic Disease
• Natural selection
• Speciation

Question 6

What is Random Genetic Drift?

Answer 6

• Refers to an allele that is rare in a large population becoming by chance become more frequent in a small population
• Is totally random, occurs purely by chance alone
• Is non directional (has no selection pressure)
  e. g. Dunkers, Bentinck Island

Question 7

What is Dunkers?

Answer 7

• Live in Pennsylvania, came from the Hesse community in Germany in the 18th century
• Their Religion does not allow them to marry outside their group and this became an isolated breeding population within the total population of the United States
• Study’s measured ABO blood types, attached or free ear lobes etc, and found Dunkers varied in allele frequency from the present day Hesse and also from the surrounding American population
• Thus Random Genetic Drift was responsible for variation, as the size of Dunkers population allowed certain alleles to become more common purely by chance

Question 8

What is the Founders Effect?

Answer 8

• Similar to Random Genetic Drift
• Occurs when a very small group moves away from homeland to a new area and establishes a community which expands and grows
• This small group is not representative of the whole population
• The group is relatively isolated which leads to a loss of genetic variation even leading to evolution of a new species
  E.g. Pingelup, Pitcairn Island

Question 9

What is Pingelup in relation to the Founders Effect?

Answer 9

• A Typhoon hit the island of Pingelup in Micronesia and killed all but 20 people, the 20 people formed the founding population of current inhabitants
• One person who carried the heterozygous allele for Achromatopsia (total colour blindness) passed this one and it became more frequent purely by chance
• In Pingelup there is a 5% of occurrence of Achromatopsia and 30% are carriers
• The Founders Effect was due to a small group relatively isolated with little immigration, gene pool is different to the original population, this founder population is unrepresentative of the original population

Question 10

What is Migration?

Answer 10

• Migration can be described as gene flow from one population to another
• Therefore if immigrants to a country bring alleles that are not already in the population, the frequencies for the alleles of that gene will be altered
  e. g. China, Europeans into Australia

Question 11

What are Barriers to Gene Flow?

Answer 11

• Populations are often kept apart by barriers that inhibit the amount of interbreeding between them
• No two environments are exactly the same, the environmental pressures on one side of the population will be different from the pressure on the other resulting in slightly different characteristics being favoured in one population compared to the other
• Isolation results in the development of a seperate gene pool
• Two examples: geographical and sociocultural

Question 12

What are examples of Barriers to Gene Flow?

Answer 12

1. Geographical Barriers
   - Oceans, large lakes, mountain rangers, desserts, ice sheets
   - e.g. Australians were isolated for many years due to ocean barriers
2. Sociocultural Barriers
   - Religion, language
   - e.g. Basque people, Pyrenees between France and Spain, developed their own language that was different to French and Spanish, they isolated themselves in terms of sociocultural barrier

Question 13

What are Genetic Diseases?

Answer 13

• Genetic diseases result in changes to the allele frequencies in a gene pool
• Usually an allele that causes death seem to disappear but some stay i.e. Tay Sachs Disease (TSD) and Sickle Cell Anaemia

Question 14

What is Natural Selection?

Answer 14

• Natural Selection is a process where a species become adapted to the environment, certain alleles can become preferred and can become a survival advantage
• It is the favouring of one set of alleles at the expense of others
• There are 6 principles of Natural Selection

Question 15

What are the 6 Principles of Natural Selection?

Answer 15

1. Variation - there is variation of characteristics within species
2. Birth Rate - there is a higher number of offspring than there are that can possibly survive to maturity
3. Struggle for Existence - there is high birth rate within a species with limited resources which lead to a species competing to survive
4. Survival of the Fittest - individuals with characteristics best suited to their environment have a greater chance of surviving and reproducing
5. Favourable Characteristics - are passed onto the next generation
6. Allele Frequencies - the proportion of alleles that produce favourable characteristics increase in the gene pool

Question 16

What are Examples of Natural Selection

Answer 16

• Sickle Cell Anaemia

- Eskimo & African Body Stature

Question 17

What is Speciation?

Answer 17

• Speciation is the formation of new and distinct species in the course of evolution
• Reproductive isolation may lead to the development of seperate gene pools
• No two environments are exactly the same, so it is expected that different alleles would be favoured in one environment more than another due to selective pressures
• Over many generations the populations will become less alike as they develops characteristics better suited to them
• In some situations some may become so different that even if the barriers to reproduce were removed, interbreeding would not be possible which leads to two separate species (speciation)