Lesson #4 Population Genetics, X2 AGRO 315 Genetics

Lesson #4 Population Genetics, X2 AGRO 315 Genetics

Questions due Monday, February 6th, 2012

1. Monarch Butterflies live an eventful life because of their life cycle and long annual migrations.

a. What is a population of monarchs?

b. When in their life cycle are monarchs intermating?

c. Use the monarch butterfly migration map to propose how many populations of monarch butterflies are found in North America. Describe the populations below.

d. An entomologist develops a small radio transmitter that can be attached to an adult monarch and does not impede their ability to fly from the Northern USA to Mexico….and back North in the spring. How could they use these radio transmitters to determine if the Monarchs that spend the winter in Mexico are one population or several populations?

e. Assume that an entomologist captures some monarchs that do not have white sections in their wings. Their wing edges are all black. They decide to do a Family genetics study to understand the genetic control of this wing spot color trait

Black X White → F1 are all Gray

Based on this result, they proposed that BB is black, WW is white and BW is gray

The entomologist hires an undergraduate as a summer employee and they capture, phenotype and release 1000 monarchs from three populations. They also generate 100 offspring from crossing their gray veined F1s above.

Population Black spots Gray spots White spots

Nebraska / 9 / 180 / 811
California / 90 / 423 / 487
Florida / 100 / 0 / 900
F2 from their F1 / 19 / 53 / 28

e. The diagrams below were drawn to show how the B and W alleles from the male and female gene pool come together to form offspring. The sizes of the boxes reflect the frequency of the B and W allele in the gene pool.

Determine which diagram represents each population or the family.

Nebraska Population: _____ California Population: _____ F2 family ____

f. Label one of the diagrams above to shown how it represents the Hardy-Weinburg formula that is used to predict genotypes given the assumption of a population in Hardy-Weinburg equilibrium. (p2 + 2pq + q2 )

Population Black spots Gray spots White spots

Nebraska / 9 / 180 / 811
California / 90 / 423 / 487
Florida / 100 / 0 / 900
F2 from their F1 / 19 / 53 / 27

g. Perform an X2 test for goodness of fit to determine if the data above for the F2 family supports the hypothesis that BB is black, WW is white and BW is Gray

h. Perform an X2 test for goodness of fit to determine if the data above for EITHER the Nebraska or the California population supports the hypothesis that random mating is occurring with respect to this wing spot color trait.

Frequency of the B allele ______Freq. of W ______

i. Propose a mating system in the Florida population that is consistent with the wing spot trait data. Justify your choice.

j. Biologists interested in monarch butterfly populations perform experiments that reveal more about factors in the environment that can impact monarch populations. Match the hypothesis with the slide # from the Monarch Life slide show on the Blackboard site.

Hypothesis #1: Monarch adults with the genotype of high fat storage have a selective advantage in the population.
Hypothesis #2: Monarch larvae are sensitive to the Bt protein toxin in the pollen of Bt corn plants.
Hypothesis #3: Monarch sensitive to loud noises along highways have a selective advantage in the population.
Hypothesis #4: Monarch larvae are sensitive to a minimum dose of the Bt protein toxin.
Hypothesis #5: Monarch larvae do not encounter the minimum dose of the Bt protein toxin in nature.

k. Rank these alleles based on which is most likely to increase in frequency in a Monarch population (1 is the most, 4 the least)? Justify your choices and use the term ‘selection pressure’ in your justification.

_____ the allele of a gene encoding a gut protein in the larvae that breaks down the Bt protein in the ‘Mexican overwintering pop.’

_____ the allele of a gene encoding a gut protein in the larvae that breaks down the Bt protein in the ‘California overwintering pop.

_____ the allele of a gene encoding a nerve protein that makes the butterfly fly away from highway noise

____ the allele of a gene encoding an enzyme that makes lipids that are stored in the adult butterfly.

l. Chose the terms migration, drift and mutation for these blanks below.

______A. A hard western wind blows in the spring and many Monarchs in California are blown into Kansas.

______B. A hurricane wipes out 50% of the smallest monarch population in Florida.

______C. A random mistake in replicating a monarch larvae’s gene encoding a digestive protein is passed on and the larvae that inherit this new trait do not get sick from the Bt protein.

2. Refer to the ABO blood group population table.

1. What is the frequency of the O allele in the Aborigine population?

b. What alleles are present in the Blackfoot population? __O __A __B

c. The best explanation for the ABO type distribution observed among the Sudanese population is that in Sudan there is what type of mating system?

____ random mating ____ positive assortive mating ___ inbreeding

The pedigree below shows the inheritance of the A,B,O blood groups in a human family.

D. Assume that ‘J’ marries a man who is a member of the Navajo population. The husband does not know their blood type. This population is randomly mating with respect to the ABO type. What is the probability that the first child of ‘J’ and her husband will be type O?

3. We have collected the following data on tongue rolling phenotypes.

36 rollers 4 nonrollers

Assume that tongue rolling people are RR or Rr and non rollers are rr.

a. What mating system do you hypothesize for the Nebraska population with respect to the tongue rolling trait.

_____ random mating ____ positive assortive mating

b. Given your mating system choice,

calculate the frequency of the R and r allele.

_____ R ____r

4. A population of Nebraskans is sampled and scored for their ear lobe phenotype on March 7, 2011. The following data are collected.

FF Floppy ear lobed 10

AF Intermediate ear lobed 24

AA Attached ear lobed 6

A allele frequency ______F allele frequency

Determine if this population is randomly mating with respect to this ear lobe trait.

Ear type / observed / expected / Dev. / Dev. 2/Exp / X2

4. Read the article “Running Blind” in PASSeL and sent to your inboxes.

Researchers have determined that the form of blindness seen in the Chloride Springs herd is recessive. Explain why they are so concerned about the extinction of this herd with only a small percentage (~5-15%) of the horses suffering from cataracts.

Describe the mating system for these horses (random mating, positive assortive mating, negative assortive mating, inbreeding?).

A trait like blindness is an evolutionary detriment to a horse, making them more susceptible to predators and injury. Explain why the blind horses of this herd do not die before reaching reproductive age. (Multiple reasons are given in the article and are acceptable.)

Explain why only removing or gelding the blind horses from the herd is not enough to eradicate the trait?

The article mentions that two dwarf horses were also found in the Chloride Springs herd. If this is also a simple recessive trait (ie only linked to one gene), and the herd is randomly mating amongst themselves (assume Hardy Weinberg equilibrium), what is the frequency of the dwarf allele, little ‘d?’ Assume 90 horses in the herd. What would you expect the frequency of heterozygous horses to be (for the dwarf allele)?