Genetics L311 Final Exam

name:______student ID:______Genetics L311 final exam December 19, 2014

Directions: Please read each question carefully. Answer questions as concisely as possible. Excessively long answers, particularly if they include any inaccuracies, may result in deduction of points. You may use the back of the pages as work sheets, but please write your answer in the space allotted. However, you must show all your work. Clearly define your genetic symbols. We will not make guesses as to what a particular symbol is intended to mean. Also, don’t assume that strains are true-breeding unless this is stated in the question. Finally, show all your work. Good luck.

(30 points possible)

total (of 200 points possible) name:______student ID:______1. Short answers (2 pts each, for total of 30 pts) A. Activation of a cell death program involves activation of cellular proteases called .

B. The mammalian gene found on the Y chromosome that specifies male development is called .

C. Traits determined by the interactions of many genes, often in combination with environmental factors, are said to be .

D. One of the hallmarks of cancer, , is the spread of cancerous cells to new sites.

E. The genes specify the development of alternating segments during Drosophila development. (I’m looking for the class of genes, not examples of members of this class.)

F. is a DNA element that can excise itself from a chromosome and move to a new position without changing the number of elements within the genome.

G. A cell or individual that deviates from a whole multiple of the haploid or monoploid chromosome complement (eg. having one extra chromosome or missing one chromosome) is said to be .

H. (H2) provides an estimate of the genetic contribution to a trait.

I. A distinct breeding group within a larger interbreeding group of individuals is referred to as a(n) .

J. The tendency of two genes located on the same chromosome to co-segregate is called .

K. The failure of chromosomes to separate during mitosis or meiosis is .

L. A plant or animal with four sets of chromosomes, regardless of their origin, is said to be .

Please provide a brief definition of each of the following: M. oncogene:

N. gene pool:

O. reciprocal translocation: 2. A recent study of autosomal dominant polycystic kidney disease in the Seychelles Islands estimates the frequency of the disease at 0.0006. Assume that this population meets Hardy-Weinberg criteria. name:______student ID:______A. What are the frequencies of the mutant and wild type alleles (6 points)?

B. What is the frequency of homozygous mutant individuals in this population (7 points)?

C. In order for Hardy-Weinberg to apply, several criteria must be met. List any three of these criteria (6 points).

3. In beetles there are three mutants, q, r, s where each mutant is recessive to its wildtype allele. A cross between a heterozygous female for all three loci and a homozygous mutant male yielded the following results:

+ r + 431 + + + 47 q + + 5 q + s 420 q r s 52 + + s 22 q r + 17 + r s 6

A. What is the order of the genes on the chromosome (4 points)?

B. What is the map distance between the three linked genes (9 points)? q-r: r-s: s-q:

Assume for the rest of the problem (warning this does not necessarily represent the correct answer for a and b) that the order and distance are the following: r 15mu q 30mu s

C. What is the probability of obtaining a phenotypic + q + offspring from a cross between a heterozygous (r q s/+ + +) flies and r q s homozygous recessive flies (4 points)? 4. Below is a signaling pathway that regulates wing development in Drosophila, among many other things. For the purposes of this question we will ignore any other functions of this signaling pathway. name:______student ID:______wnt frz gsk3 cat tcf wing

What phenotypes do you expect mutations in the following to produce? Note: All mutations are loss-of- function unless otherwise indicated (gf = gain of function, assume this produces the equivalent of continuously active protein, 8 points).

wnt (gf)

wnt (gf); tcf

5. A. We looked at the genetic pathway that determines gender in C. elegans. The pathways is shown below. What phenotype would we expect to see result from the following mutations (8 points)?

if X:A=0.5 if X:A=1.0 loss of xol-1 loss of fem-2 loss of tra-2 loss of tra-2 and loss of fem-2

B. Most developmental pathways are conserved from simpler to more complex animals. An exception to this general rule is provided by sex determination. Please list three ways in which sex determination is not conserved between C. elegans, Drosophila and mammals (6 points).

6. Progression through the cell cycle is tightly regulated. In particular, we looked at how the cell regulates entry into S phase. A. Please illustrate the steps involved in a cell’s decision to enter S phase. Include the relevant proteins. You may use a diagram if you wish (6 points). name:______student ID:______

B. Cells use several different checkpoints to verify that essential steps are completed before proceeding to the next event during the cell cycle. Please show how the cell arrests in the cell cycle prior to entry into S phase if DNA damage is detected. Include the relevant proteins (6 points).

C. Using the pathway discussed in lecture, first determine whether the following mutations would increase or decrease the probability of cancer, or have no effect. Please briefly state your rationale (12 points).

Mutation Probability Rationale

Loss of Rb

Loss of Ras

Loss of Bcl2

Loss of Rb plus overexpression of Bcl2

7. The rare deepwater jellyfish K. hunterae is a diploid with two pairs of chromosomes, one long and one short. Mutations in the lng gene cause animals to develop extremely long tentacles, mutations in blu cause them to lose their normal blue spots and mutations in bky cause them to develop enlarged beaks. A particular individual, named Fred, is heterozygous for lng and blu, which are on the long chromosome, and homozygous mutant for bky. You demonstrate that the lng and blu mutant alleles are in the cis configuration. bky is not linked to lng or blu. name:______student ID:______A. Diagram all of the possible gametes that can result from meiotic division of Fred’s cells, including gametes that would be formed. Include genes. Assume a single cross over between lng and blu (5 pts).

C. You find an unusual K. hunterae individual who is triploid. Please diagram this individual’s chromosomes in the most likely arrangement in metaphase of meiosis I. You need not include genes. Please draw a circle around one set of homologues and a box around a single pair of sister chromatids (6 points).

8. When traveling in a cave near Bloomington, you came across a species of bat, C. smithae. Two recessive mutations are known, one causing glow-in-the-dark wings (g) and the other causing hairy feet (h). When trying to create a monster bat for a reality TV show, you cross heterozygous parents, both with the mutations in trans, hoping to produce bats with hairy feet and glowing wings. Since the mutations are only 4 mu apart you assume no double crossovers. What percentage of offspring will have glowing wings and hairy feet (8 points)?

9. You have cloned the soc gene from mouse, a gene that you hypothesize promotes social behavior. A. What would be the best test of your hypothesis? Please include the steps involved and a diagram of the vector used in the experimental procedure (8 points). name:______student ID:______

B. To further understand the function of soc, you wish to determine where in animals the gene is expressed. What method would you use to obtain this information? Please include a diagram of the vector that you would use but you do not need to include the steps involved (6 points).

10. In C. elegans, cell-cell signaling specifies vulval cell fates, causing the Pn.p cells to adopt primary, secondary or tertiary fates. Give the predicted affect of the following mutations in each of the cell fates listed (i.e. increase, decrease or no change for each cell type, 3 pts each, 15 pts total):

primary tertiary rationale

A. loss of lin-3/EGF

B. gain-of-function mpk-1 (kinase downstream of Ras)

C. gain of mpk-1 plus loss of EGF

D. loss of transcription factor (lin-1 or lin-31)

E. gain of mpk-1 plus loss of transcription factor

11. While exploring the outer regions of the galaxy, Captain Kirk and his crew discover a unique creature called a Tribble. Tribbles are fuzzy, round, purring creatures that can reproduce very quickly and make great pets. So merchants at the nearby Starbase are very interested in tribble genetics. Specifically, they want to know about the genetics of the three most common colors: black, white and tan. A purebred black tribble is bred to a purebred white tribble. F1s are crossed to give the F2s shown below: 453 Black name:______student ID:______301 Tan 49 White

A. Please give the genotypes of the F2s shown above (8 points).

B. White tribbles from the F2 generation are crossed to black tribbles from the F2 generation. What is the probability of getting tan tribbles from this cross (6 points)?

C. A few tribbles are found to have unusually short fur. Short-furred males are crossed to wild-type females producing the F1s shown below. Short-furred F1 males are then crossed to short-furred female F1s to produce the F2s shown below.

F1s: F2s ½ long furred 2/3 short furred ½ short furred 1/3 long furred

How do you explain these results (6 points)?

12. Imagine that you are counseling a couple who have just had a child born with Down syndrome, which typically results from trisomy 21. The couple’s first child was also affected by Down syndrome. When you examined the child’s karyotype you find 46 chromosomes. A. How might you explain this result (5 points)?

B. The couple wish to have another child. Which of the following provides the best estimate of the probability that the couple’s next pregnancy will be affected by Down syndrome (3 points)? i. the couple’s next pregnancy is certain to be affected by Down syndrome (probability = 1) ii. the couple’s next pregnancy is certain not to be affected by Down syndrome (probability = 0) iii. the probability is the same as for the general population, which is ~1/25,000 iv. the probability is higher than the general population risk, and may be as high as 1/3 v. based on Mendelian principles, the probability is exactly 1/2

13. Kennedy disease is a disorder that causes muscle cramps and progressive weakness. The following is a human pedigree of a family affected with this disorder. Kennedy disease is extremely rare in the population. name:______student ID:______

A. What is the most likely mode of inheritance of this disorder (2 points)?

B. What are the genotypes of the following individuals in the pedigree (6 points)?

I-1: II-2: III-2:

C. What is the probability that individual IV-1 will be affected (2 points)?

D. What is the probability that III-7 carries the mutation that produces Kennedy disease (2 points).