Week 22: Hardy-Weinberg

Question 1

Question on page 5

Question 2

Question on page 7

Question 3

Population:

Answer 3

a group of individuals of the same species living in the same (arbitrarily defined) area.

Members of a population are more likely to breed with each other than with members of another population

Question 4

Gene pool:

Answer 4

all the alleles of all the genes in all individuals of a
population

Question 5

Fixed allele:

Answer 5

when all individuals in a population are homozygous for one allele. No other alleles for that locus exist in the population.

Question 6

Question on page 11

Question 7

The frequency of a phenotype (i.e., a trait) =

Answer 7

Number of individuals with the phenotype / total number of all individuals

Question 8

Question on page 13

Question 9

Question on page 15

Question 10

The frequency of an allele in a population =

Equation:

page 17 for visuals*

Answer 10

its proportion in a population

number of copies of allele / total number of all copies of all alleles for that gene

Question 11

Question on page 18

Question 12

If a population’s expected frequencies match its observed frequencies, and this does not change, then the population is at ______________

Answer 12

equilibrium

Question 13

The Hardy-Weinberg assumes what is not occuring

Answer 13

1. Natural selection
2. Genetic drift
3. Gene flow
4. Non-random mating
5. Mutation

Question 14

The Hardy Weinberg equation:

Answer 14

Let p = frequency (proportion) of the dominant allele

Let q = frequency (proportion) of the recessive allele

p + q = 1

therefore

p^2 + 2pq + q^2 = 1

Question 15

Question on page 23

Question 16

The Rule of Multiplication

Explanation on page 25

Question 17

There are TWO WAYS an individual could inherit one dominant and one recessive allele:

Answer 17

1. A sperm carrying a dominant allele (frequency = p) could fertilize an ovum carrying a recessive allele (frequency = q); odds = p*q (Aa)
2. A sperm carrying a recessive allele (frequency = q) could fertilize an ovum carrying a dominant allele (frequency = p); odds = q*p (aA) = Aa

Question 18

The Rule of Addition:

Answer 18

The probability of an event that can occur in two or more different ways is equal to the sum of the individual probabilities of each way

Odds of being a heterozygote are therefore
(p * q) + (q * p) = 2pq

Question 19

The HW equation only applies to populations that are ……

Answer 19

NOT evolving

Question 20

Question on page 32

Question 21

Question on page 34

Answer 21

c) 0.04

q^2= aa

0.2 x 0.2 = 0.04

Question 22

Question on page 36

Answer 22

e) 96%

p^2 + 2pq = AA

(0.8)^2 + 2(0.8)(0.2) = 0.96

0.96 x 100 = 96%

Question 23

Causes of evolution:

Answer 23

1. Natural selection
2. Genetic drift
3. Gene flow
4. Non-random mating
5. Mutation

Question 24

why does the Hardy weinberg equation no longer predict genotype frequencies accurately when natural selection acts against a trait

Answer 24

When natural selection acts against a particular trait, it disrupts the balance described by the Hardy-Weinberg equilibrium. Natural selection favors certain alleles over others, leading to changes in allele frequencies within the population.

If a trait is under negative selection (disadvantageous), individuals with the corresponding genotype will have reduced fitness and are less likely to survive and reproduce. As a result, the frequency of that genotype will decrease over time, disrupting the equilibrium predicted by the Hardy-Weinberg equation.

Question 25

Review slide 43-46

Question 26

Huntington’s disease

Answer 26

A disorder of the nervous system.

Question 27

Huntington’s disease - when do symptoms begin to appear? When do they become fatal?

Answer 27

Symptoms usually begin to appear between the ages of 35 and 45

Fatal within 15-20 years of the onset of symptoms.

Question 28

Huntington’s disease associated with dominant or recessive allele

Answer 28

Huntington’s disease associated with dominant allele

Question 29

Practice question page 56 - 58

Review lab 6 quiz and Quiz 6 on eclass for practice

Question 30

Which is true of populations that are in Hardy-Weinberg equilibrium?

Question 2 Select one:

a.
Natural selection is occurring.

b.
The populations must be very small.

c.
Mating is random.

d.
Organisms are constantly migrating.

e.
All of the above are true.

Answer 30

c. Mating is random

Question 31

Why is the concept of Hardy-Weinberg Equilibrium useful in evolution?

a.
When predicted genotypic frequencies match observed genotypic frequencies, we can accurately predict which genotypes are advantageous.

b.
When predicted genotypic frequencies match observed genotypic frequencies, we can assume that evolution is occurring at a steady rate.

c.
When predicted genotypic frequencies match observed genotypic frequencies, we can assume that the population is not evolving.

d.
When predicted genotypic frequencies match observed genotypic frequencies, we can accurately determine which alleles were under selection in the past.

e.
When predicted genotypic frequencies match observed genotypic frequencies, we can say that evolution is definitely occurring.

Answer 31

c.
When predicted genotypic frequencies match observed genotypic frequencies, we can assume that the population is not evolving.

Question 32

Natural Selection acts on:

Select one:

a.
Genotypes

b.
Phenotypes

c.
Individuals

d.
Both A and C

e.
Both B and C

Answer 32

e.
Both B and C

Question 33

Frogs are particularly vulnerable to an invasive pathogen called chytridiomycosis (chytrid fungus). When chytrid fungus is introduced to new populations, the disease can kill nearly all the individuals. However, those few individuals who escape the disease have some degree of resistance to the fungus.

True or False: this scenario represents a beneficial bottleneck event, leading to higher reproduction and fitness for those individuals that survive the bottleneck.

Select one:
True
False

Answer 33

True