Question

25. In dogs, you discover that one gene influences ear shape. One allele (allele D) is associated with droopy ears and is dominant to a second allele (allele d) which is associated with upright (pointy) ears.   Describe the simplest and cleanest method for determining if this gene is sex-linked. EXPLAIN your answer. (5)

26. After you answer the question above, you discover a third allele for ear shape gene in dogs. This allele (t) produces stunted (or stubby) ears and is recessive to the other two alleles. What is the easiest method for determining whether or not this allele is sex-linked? Remember that you want to save time and money. (2)

27. Mongers have a diploid number of 12. The following genes are located on the same chromosome:

Chromosome number 1: genes A and B

Chromosome number 2: genes D, E and F

Chromosome number 3: genes G and H

Chromosome number 4: genes P and Q

Chromosome number 5: genes R and S

Chromosome number 6: gene T

A. You cross a monger that is AA-BB-DD-EE-FF-GG-HH-PP-QQ-RR-SS-TT to one that is aa-bb-dd-ee-ff-gg-hh-pp-qq-rr-ss-tt.

Consider the F1 offspring: AaBbDdEeFfGgHhPpQqRrSsTt

Draw what a cell would look like during metaphase I of meiosis. Draw ONLY ONE of the possible arrangements of chromosomes and label the chromosomes.

B. If no cross over of genetic material occurs, how many genetically different gametes can be produced by this individual?

C. If cross over does occur, how many genetically different gametes can be produced by this individual?

D. You have an individual Monger that is AABbDDEeFfGgHhppQQRrSStt........ If no cross over of genetic material occurs, how many genetically different gametes can be produced by this individual?

E.If cross over does occur, how many genetically different gametes can be produced by this individual?

Answer 1

25. A) If the ear shaped gene is sexlinked then it will be located on X chromosome. now if we cross one pointy ear female with a droopy male and the male offspring obtained from it has pointy ear then the gene is located on x chromosome. if the gene is not sex linked then we get both droopy and pointy male.

B) In this case multiple allele, so if cross a pointy female with a stubby male and the male produced from this cross has droopy ear then the gene is sexlinked.