Topic 4

Question 1

What is a gene?

Answer 1

The combination of two alleles

Question 2

What is an allele?

Answer 2

Variation of a gene on chromosomes. Mom has blue eye allele and dad has brown eye allele

Question 3

What is genetic variation?

Answer 3

The diversity of alleles in a population. Allele varieties=genetic variation

Question 4

What is phenotype variation?

Answer 4

Variety in the visible expression of “types”. Is caused by genotype and environment

Question 5

Where and how does natural selection operate?

Answer 5

Natural selction operates at the phenotype. It operates with the use of environment and genotype

Question 6

What is statistical variation?

Answer 6

Measures the difference from an average value. So like is a graph line really thin or thicker?

Question 7

What is evolution?

Answer 7

Change in the frequencies of alleles in a population between generations

Question 8

What are the five factors that can change allele frequency?

Answer 8

Natural Selection, Sexual selection, mutations, gene flow and genetic drift

Question 9

What is sexual selection?

Answer 9

It is non random mating and is due to preferred phenotypes. It may decrease genetic variation

Question 10

What is non-random mating?

Answer 10

Increase or decrease in the probability that a specific individual will mate

Question 11

What are mutations?

Answer 11

A change in an individuals DNA that can be cause by an error in DNA replication or by structural damage to DNA. It is random, meaning it is unaffected by environment and can be good, bad or neutral

Question 12

What is Gene Flow?

Answer 12

The transfer of alleles between populations. It increases the variation within a population but decreases the variation between populations

Question 13

What is genetic drift?

Answer 13

Changes in allele frequency due to chance (regardless of Natural Selection). Allele frequencies “drift” from one generation to the next. The impact of drift is greater on smaller generations. Rare alleles are more likely to be lost due to drift. Examples are founder effect and bottleneck effect

Question 14

What is the founder effect?

Answer 14

A new population is established by a few colonizers. There is a small fraction of genetic variation compared to the ancestral populations and change in allele frequency

Question 15

What is the bottleneck effect?

Answer 15

Only a few individuals survive something (natural disaster, etc.) and so these few are the only ones that produce the next generation. Therefore the gene frequency in the next generation is different then previous generation

Question 16

What are the mehanisms of Natural Selection?

Answer 16

Directional Selection, Disruptive Selection and Stabilizing selection

Question 17

What is directional selection?

Answer 17

An extreme phenotype is favored because it has highest fitness. Frequency distribution of alleles shifts which can cause the lose of allelic variations and the loss of genetic variation. Loss of genetic variety but same phenotypic variation

Question 18

Does statistical variation change in direction selection?

Answer 18

Directional selection is a directional shift in the mean of the population. Statistical variation doesn’t change. As in the curve of a graph doesn’t change it just shifts

Question 19

What is Disruptive Variation?

Answer 19

Two extremes are favored and results in polymorphism. It maintains genetic variation but changes phenotypic variation. So two types of dark butterfly are favored and the light butterfly begins to die off. Creates graphs with 2 extremes. There is a disadvantage to be the average phenotype

Question 20

What is polymorphism?

Answer 20

2 or more divergent phenotypes

Question 21

What is stabilizing selection?

Answer 21

The intermediate or common phenotypes are favored, there is selection against extremes which eliminates harmful mutations. The mean of the population stays the same (variation decreases) and there is little or no evolutionary change (maintains genetic variation). Graph becomes thinner

Question 22

How do you maintain Genetic variation despite natural selection?

Answer 22

Mutation, Recombination, Fertilization, Independent assortment, disruptive selection, gene flow, negative frequency dependent selection and heterozygote advantage

Question 23

What is negative frequency dependent selection?

Answer 23

The rare genotype has the advantage

Question 24

What is heterozygote advantage?

Answer 24

Heterozygotes have the advantage over homozygotes. Think sickle cell anemia

Question 25

Why cant Natural Selection craft perfect organisms?

Answer 25

Selection can only act on existing variations, evolution is limited by historical restraints, adaptions are often compromises and chance, natural selection and environment interact