Biol 415: Lecture 8 (9/22/15)

Front 1

Explain why this is considered additive alleles

Back 1

When the heterozygous is in the middle then it's additive and there is no dominance.

Front 2

Explain why this is considered D allele dominant

Back 2

The heteozygous phenotype follows the dominant allele it has nothing to do with fitness

Front 3

Explain what is happening in the image.

Back 3

The recessive allele (yellow line) is being selected against by the dominant allele (red line). This kind of graph is common when dominant allele is advantageous. The way the yellow line is progressing makes sense because initially when the recessive allele is common, evolution is fast and as the recessive allele becomes rare, evolution slows.

Front 4

Explain why when recessive allele is rare, evolution is slow

Back 4

Most recessive alleles are hidden in heterozygotes and therefore immune from selection

Front 5

Describe what is happening in the photo

Back 5

This is describing recessive alelle advantage. The slow increase is due to the fact that the majority of recessive alleles were heterozygous. Eventually the homozygous dominant allele becomes over taken by the recessive homozygous allele.

Front 6

What eventually happens with a beneficial recessive allele in a population?

Back 6

In the event that the benefiical recessive allele is being selected for then the recessive allele will become fixed in the population and becomes the dominant allele.

Front 7

In the event that a recessive allele is deleterious what hapenes to the allele when the recessive allele becomes rare.

Back 7

Most recessive alleles are in the heterozygous state and are masked from selection. This is the reason why the rate of its disappearance is slow.

Front 8

In the event that a dominant allele is deleterious what hapenes to the allele when the recessive allele becomes rare.

Back 8

Dominant alleles that is disfavored by selection is removed quickly from the population

Front 9

Explain the image

Back 9

Because the heterozygous is advantageous this shows Overdominance and neither allele is dominant.

Front 10

Explain the image

Back 10

Because the heterozygous is disadvantageous this shows Underdominance and neither allele is dominant.

Front 11

Explain this image

Back 11

This shows heterozygous advantage specifically Overdominance.

Front 12

Sickle cell disease is an example of

Back 12

Overdominance. Heterozygote superiority maintains genetic diversity at the human locus for hemoglobin. AA individuals are free of disease. Recessive allele (s) causes sickle-cell disease in homozygous individuals (ss). Heterozygous individuals (AS) are resistant to malaria. However, this is only overdominant in certain environments such as environments that are prevalant in malaria.

Front 13

What is the parasite that causes malaria?

Back 13

Plasmodium

Front 14

Where is the frequency of sickle-cell allele (s) highest?

Back 14

The frequency is highest where the malarial parasite is common

Front 15

Explain this image

Back 15

This image shows a homozygous advantage underdominance. There are two possible outcomes depending on initial allele frequency and fitness of homozygotes, one allele evolves to fixation (1.0) while the other allele is lost (0.0)

Front 16

Explain this image

Back 16

This image shows the heterozygous advantage equilibrium (overdominance)

Front 17

Explain this image

Back 17

This image shows the homozygous advantage equilibrium (underdominance)

Front 18

Why does this graph show two equilibriums?

Back 18

The two equilibriums are representative of the two homozygotes

Front 19

A mechanism promoting balanced polymorphism. A phenotype has higher fitness when it is rare, and lower fitness when it is common.

Back 19

Frequency dependant selection

Front 20

Bumblebees have been attracted to purple flowers lately when they have been rare. Eventually, due to the high pollenation of bees, the number of purple flowers increased. Now bumblebees have been attracted to yellow flowers when they have been rare. This is an example of

Back 20

Frequency dependent selection

Front 21

Differential reproduction is caused by differences among individuals in what traits?

Back 21

1. Mortality

2. Fertility (offspring)

3. Fecundity (gametes)

4. Mating success

5. Viability of Offspring

Front 22

T/F: Natural selection can be enforced on every part of the life cycle

Back 22

True

Front 23

What is the target of natural selection?

Back 23

Fitness

Front 24

The measure of the individual's ability to survive and reproduce

Back 24

Fitness

Front 25

How is the size of a population constrained?

Back 25

The carrying capacity of the environment

Front 26

An individual's evolutionary success is determined not by ______________ but by its ___________________ in comparison to the other genotypes in the population

Back 26

Absolute fitness; relative fitness

Front 27

The fitness of an individual relative to the population mean

Back 27

Relative fitnes

Front 28

Contributing 100 offspring sounds good unless an average individual in the population contributes 200 this is an example of

Back 28

Relative fitness

Front 29

What is the formula to find relative fitness?

Back 29

Absolute fitness/average fitness

Front 30

What are the two outcomes of Natural Selection?

Back 30

1. Stasis: Maintain the allele frequency in a population

2. Change: Changing allele frequency

Front 31

T/F: Fitness is only dependent on the genes

Back 31

False. Fitness is dependent on the gene and on the environment. (Ex. Sickle cell's ability to be beneficial or deleterious is dependent on where you live)

Front 32

The actual vaibiliy or reproductive success of genotypes

Back 32

Absolute Fitnesses

Front 33

The fitness of a genotype relative to the population's Average Absolute Fitness

Back 33

Relative Fitness

Front 34

How much will natural selection change q, the frequency of the sickle cell allele in the population if W>1?

Back 34

The genotype will increase in frequency

Front 35

How much will natural selection change q, the frequency of the sickle cell allele in the population if W<1?

Back 35

The genotype will decrease in frequency

Front 36

Based on the relative fitness what can you determine about the "S" allele?

Back 36

The "S" allele appears to be a recessive deleterious allele given that the Wss is less than 1 indicating a decrease in frequency.

Front 37

Based on the relative fitness what can you determine abou tthe "S" allele?

Back 37

The "S" allele appears to confer a heterozygous advantage indicating overdominance. This also indicates that the heterozygous allele will increase in the next generation

Front 38

What is true about s and t when they are negative using the following equation:

P=t/(s+t)

Back 38

There is overdominance and a stable equilibrium exists

Front 39

Genotype fitness for the hemoglobin gene in West Africa is

{WSS, WSs, Wss}={0.6, 1.0, 0.1}

Equilibrium frequency of an allele when there is heterozygote advantage, is determined by the selection coefficients of the homozygotes.

P=t/(s+t)

How will the allele frequency change in the long term?

A. Allele S will increase until it is fixed in the population

B. Allele S will converge around 0.69

C. Allele S will converge around 0.31

D. Allele S will decrease until it is removed from the population

Back 39

WSS = 1+s ; WSs = 1 ; Wss = 1+t

S=-0.4 ; t=-0.9

p=t/(s+t)

p=-0.9/(-0.4-0.9)

p=0.7

B. Allele S converge around 0.69

Front 40

Match the scenario below with the correct type of selection that likely acts on the population.

A. Dominant allele advantage

B. Recessive allele advantage

C. Heterozygote advantage

D. Homozygote advantage

E. Frequency dependent

a pocket mouse species inhabits an island covered with two kinds of habitats, the dark basaltic rocks and light sand dunes. The mice color is determined by a locus with alleles D and d. The DD mice are dark and blend well on the dark rock. The dd mice are light and blend well on the sand dunes. Dd mice are intermediate and don't blend well on either surface.

Back 40

D. Homozygote advantage