Q1. Fill in

In 2016, The American Sheep Industry Associationreleased data showing that the nation's 88,000 sheep producersgenerated a total economic impact of $5.8 billion. Some of theissues that impact the profitability of sheep include their coatcolor, how quickly they gain weight, and whether they are resistantto infection caused by parasitic worms called nematodes. In the UKlast year, approximately 100 million dollars were spent on reducingand curing worm infections in sheep. Ateam of researchers led my Riggio and Matika are working onunderstanding the genetics of sheep in order to increaseprofitability. While sheep have hundreds of thousands of genes ontheir total of 54 chromosomes (n=27), the researchers are focusingon 3 genes. The NR gene is correlatedwith nematode resistance and is located on chromosome 14. Onlyindividuals with two recessive copies show resistance to nematodeinfection. The GTH gene is correlatedwith growth rate and overall bodyweight. The researchers would liketo have sheep grow quickly so they are ready for market sooner.Individuals with GG or Gg grow the fastest and reach market weightsooner than individuals with gg. Finally,there are two genes involved in coat color. They are both onchromosome 3, meaning they are linked. The first determines if theindividual is Black (BB or Bb) or brown (bb). The second determineif there are white spots on the coat. The spotting gene shows nospotting with the NN genotype, spotting only on the head with theSN genotype, and spotting covering a majority of the body with theSS genotype.

Q1 Fill in the table below to help you keep track of thegenes.  

Chromosome #          PossibleAlleles            PossibleGenotypes                Resulting Phenotyp

3                                      B orb                            BBor Bb or bb Black, black, brown

Coat Color S or N   

13

GrowthRate                 G or g

14

Nematode Resistance      R orr

Q2. In order to confirm that the NR gene controlsresistance to infection from nematodes, the researchers want toperform a study to test their idea that individuals with thegenotype “rr” have a lower risk of getting infected by nematodesthan individuals with RR or Rr genotypes.

a. What is the null hypothesis for thestudy?

b. What is the alternative hypothesis for thestudy?

The methods used in the study are explained below:

The genotype of 300 baby sheep were determined prior to thestudy and approximately the same number of genotype RR, Rr and rrwere used. They were raised in the same pastures and fed similarfood. Fecal samples were collected from the rectum of the babysheep at approximately 16, 20 and 24 weeks of age. Fecal egg countsof nematodes were measured on four replicates of each fecal sampleand the average of the four replicates at each time point was usedfor analyses.

Q3. Draw a figure that would show support for thealternative hypothesis. Make sure to clearly label your axes,values (tick marks), and include an appropriate figure legend belowthe figure.

Q4. One of the sheep in the study is Dolly. She is brownwith spotting on her head. She is heterozygous for the growth rategene and shows resistance for nematode infection.

a. What is the genotype of Dolly?

b. Draw one of Dolly’s cells during metaphase ofmitosis. Show chromosomes 3, 13, and 14. Label all the alleles.Label sister chromatids once in your model. Label homologous pairsonce in your model.

c. Describe what the products of mitosis would be forDolly.

d. Describe one reason why Dolly would need to performmitosis.

A new Spartan sheep farm is starting to increasetheir flock and they are going to breed two sheep to produce avariety of colors and high resistance to nematodeinfection.

A female named Sally with the genotype: Bb NN rr GG witha male, Buster, with the genotype bb SN rr Gg

Q5. Draw a puffy stick chromosome model showing forchromosomes 3, 13, and 14 for Buster before DNA replication.Clearly show the locus for the genes and label the particularalleles.

Q6

a. Are there homologous pairs in this model? State Yesor No and explain you know.

b. Are there identical sister chromatids in this model?State Yes or No and explain.

Q7. Draw puffy stick chromosome models showing thehomologous pairs for chromosomes 3, 13, and 14 Buster duringmetaphase of Meiosis I. Represent the two possible alignments ofthe chromosomes, due to independent assortment in A) and B).Clearly label all alleles for all genes. Also, label the sisterchromatids and homologous chromosomes in at least 1 instance inyour drawings if they are present.

Q8. Draw puffy stick chromosome models showing thehomologous pairs for chromosomes 3, 13, and 14 Buster duringmetaphase of Meiosis II for alignment A above AND then the finalproducts.   Clearly show the locus for the genes andlabel the particular alleles.

Meiosis II, Alignment A:

Final Products of Meiosis II for Buster in AlignmentA:

Q9. For Q7 and Q8, Write haploid or diploid next to eachmodel. Then below explain how you know the difference:

Q10. In the space below, draw the Punnett square for thecross between Sally and Buster

Sally with the genotype: Bb NN rr GG            Buster, with the genotype bb SN rr Gg

Q11. What would be the expected percentage or fractionof the offspring that would be brown with spotting on the head, beresistant to nemotodes and be heterozygous dominant for growthrate?

Q12. If you had 5 generations in a row of sheep thateither had no spotting or had spotting only on the head and then ababy sheep appeared with spotting all over the body, what is onepossible explanation? Explain your thinking.

Q13. If these scientists wanted to put the “n” alleleinto goats to help fight nematode infection, would they be doinggene editing or creating a genetically modified organism?Explain?

Only need questions 5-13 if you can understandit