Exercise #3 Genetics Name___

Lesson #3 Epistasis, Quantitative traits, X2 AGRO 315 Genetics Questions due Monday, January 30, 2012

A B C D E

brown bb E_ black B_ E_ yellow __ ee 1. Dog Breeders have determined that two gene pairs work together to control coat color as shown above.

#2 Black and Yellow lab families can be true breeding.

Crossing Yellow X Black

Black X Yellow

F1 all Black F2

9/16 3/16 4/16 Black Brown Yellow

Genotype of a. What genotypes of yellow labs are true breeding for yellow?

b. What genotype of black labs are true breeding for black? c. What would be the genotype of Black labs that would produce a 9:3:4 ratio of Black to Brown to Yellow in their offspring? d. Is the ‘B’ allele is dominant to the ‘b’ allele , or does it show a lack of dominance? The VetGen company sells genotype information on specific dogs to the dog owners. (link in lesson #3) http://www.vetgen.com/color.html e. How many different Labrador genotypes with respect to these coat color genes should they be able to identify with their tests? f. The function of the genes Vet Gen tests for are described below. #3

Test #1: A gene encodes a protein Test #2. A gene encodes a protein That allows pigment to get deposited That is an enzyme that converts In the hair fibers. Brown pigment to Black pigment

What gene is this?____ What gene is this?____ Use symbol B,b,E or e Use symbol B,b,E or e

Test one tests for ____ B allele vs. b allele ___ E vs. e g. The pedigree below shows the inheritance of coat colors in a family of Labrador dogs. Which of the dogs above would you pay to have tested by VetGen? Would you test both the E,e and B,b genes or just one of the pairs (if so, which one)

A B C D E

brown bb E_ black B_ E_ yellow __ ee h. You notice dog I has a black nose so it must be what genotype?______i. Predict the change that J will be Yellow coated and have a Black nose.

2. Classify the following traits as Quantitative or Qualitative. Justify your choice. See the link in the Quantitative trait folder for more information to help you chose.

Discussion board question, worth 6 points of total score.

Organism Trait Quant vs. Qual Justify

Humans IQ

Dogs Hip Health

Corn Grain Yield

Horses Coat color

Humans Eye color

Soybean Leaf color 3. UNL Animal Science professors use mice to study important traits in livestock. One important trait is the genetic control of energy balance. Assume the true breeding mouse lines represent a high energy line and a low energy line. Energy is measured by putting the mouse in a special cage at night and then measuring the total amount of heat the mouse gives off during the night. High energy mice give off more heat.

Assume the a line of mice have a high energy and low energy line of mice are crossed. Line A High energy Line B low energy eeHHIIjjQQRRtt X eehhiiJJqqrrtt

The E,e,H,h I,i, J,j,Q ,q, R,r and T,t genes control energy. The uppercase genes all add the same amount to energy level while the lower case genes do not add to energy level.

A. What is the expected genotype of the F1 mice made from crossing these two parents?

B. How many kinds of gametes can the F1s make with respect to these genes?

C. You mate F1 males with F1 females, how many genotypes are expected in the F2 ?

D. Assume the mouse heat measuring box is set up to read 100 heat output units for mice that are the genotype eehhiijjqqrrtt and 240 units for EEHHIIJJQQRRTT mice. Each additive gene adds how many heat units to baseline metabolism?

E. What would be the energy level of line A?______

Line B?______The F1s ?:______F. How many different energy level phenotypes are expected in the F2s assuming the mice are fed the same diet, the same amount of this food, have equivalent health, are never showed scary pictures of cats or old “Mighty Mouse” reruns and essentially live the same dull life in the mouse lab?

G. List six genotypes of F2s that would be different than the F1 but have the same energy level.

H. Draw a graph showing the distribution of energy levels of the F2s expected given they are all subjected the same environment.

I . What would be the expected frequency of F2 progeny that have a energy level of 100 units? J. Explain why F2 mice with an energy level of 150 are more common than F2 mice with an energy level of either 100 or 200

K. Variation among the F1 mice is from 145 to 155 heat units. The variation is due to.

___ environment ____ genetics ____ genetics and environment

L. Explain why variation among F2s is larger than the variation in this trait in the F1.

M. Assume Dr. Merlyn Nielsen does a selection experiment with four groups of mice. Match the description of each group with the letter from the graph. 250 A 220 B 200 C t

a 180 e H 160

140 D 120

100 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Generations of Selection ____Energy level heritability of this mouse groups is .05, top 20% of mice selected each generation.

___ Energy level heritability of this mouse groups is .75, top 20% of mice selected each generation.

___ Energy level heritability of this mouse groups is .45, top 20% of mice selected each generation.

____ Energy level heritability of this mouse groups is .75, top 2% of mice selected each generation. However, the level of variation among the selected mice is greatly reduced after early generations of selection. 4. Assume that in the future, Dr. Nielson’s research leads to the discovery of these metabolism genes and the same genes found in mice are also found in pigs. Dr. Rodger Johnson in the animal science department decides to use this information to improve meat traits in pigs. In this case, high metabolism is desired because they are the leaner pigs. He currently has a lean herd of pigs and wants to make leaner pigs. He has the choice of crossing his pigs to the two boars below.

Sows leanness genotype Boar’s leanness genotype

eeHHIIJJQQRRtt X Finnish Landrace eehiijjQQRRTT Krskopolje eeHHIIJJQQRRtt

A. Which boar when mated with your sows would produce offspring with the leanest genotype:

_____ Finnish Landrace ____ Krskopolie ____ Both the same

B. Assume that the pigs produced from these matings are the start of your new herd and you will intermate the pigs to produce more pigs to test for leanness. Which founding boar should be used if you hope to select offspring from your new herd with improved leanness:

_____ Finnish Landrace ____ Krskopolie ____ Both the same

C. The herd expected to have the highest broad sense heritability for leanness would be the one founded by crossing your sows with …(hint: environment will influence this trait)

_____ Finnish Landrace ____ Krskopolie ____ Both the same 5. Use the data set below to test the hypothesis that these two traits are controlled by single independently assorting gene pairs with complete dominance.

Show your work including the P value and your conclusion.