name:______
student ID:______
Genetics L311 exam 3
November 21, 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.
page 2______(20 points possible)
page 3______(30 points possible)
page 4______(20 points possible)
page 5______(18 points possible)
page 6______(12 points possible)
total______(of 100 points possible)
1. Short answers (2 points each, 20 points total)
A.An organisms with four sets of chromosomes, all derived from the same species, is said to be .
B.A cell or individual with some deviation from a whole multiple of the haploid or monoploid chromosome complement (eg. having one extra chromosome or missing one chromosome) is said to be .
C.Usually sterile, are the rare products of defective chromosome segregation in which the individual has only one copy of each of the chromosomes.
D.The , major sites of ATP synthesis, are small cytoplasmic organelles that include their own genomes.
E.The ability of some phage to transfer only a specific portion of a bacterial chromosome between bacteria is called .
F.The general approach of moving from a cloned gene to identifying a mutation in that gene is called .
G.Expression of as few as four genes in differentiated cells can cause them to de-differentiate, producing cells.
Please provide concise definitions of the following terms:
H.nucleoid:
I.prophage:
J.restriction endonuclease:
2. You have decided that you really want to get into the movie business and furthermore that your first movie will be about sharing your life with 3 genetic clones of yourself. To make it authentic you decide that you should first generate those three clones of yourself.
A. Please describe briefly how you will go about cloning yourself (8 points).
B. At present cloning is fraught with difficulty. Please give two ways in which your attempt to clone yourself might go awry (I’m not looking for reasons why your clone might be different from yourself but rather potential problems with the process itself (4 points).
3.After being marooned on an uninhabited island, you discover an interesting species of beetle. You observe two different strains: one with blue wings and another with red wings. You decide to cross true-breeding blue-winged females with true-breeding red-winged males. The resulting progeny are all blue-winged. You then cross the F1’s, which results in all blue-winged F2’s.
A. What modes of inheritance are consistent with these results (6 points)?
B. After lighting a signal flare, you decide you still have time to cross the F2’s together before being rescued. You find that the resulting progeny are a mix of blue-winged and red-winged. Which of the modes of inheritance that you listed above best explains this new result (6 points)?
C. What is the phenotypic ratio observed in the F3 generation (4 points)?
D. After being picked up by the Coast Guard, you head straight to the lab and clone the gene responsible for the beetle’s wing color. You then sequence the DNA. The following autoradiogram shows the sequence of a small region of the gene. What is the sequence of this region? Be sure to indicate the 5’ and 3’ ends (2 points).
4.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 (4 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 (2 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
5.You have identified mutations in a gene, asm, that produces short hair in the rare Himalayan Yeti. To understand its function, you decide to clone the gene. Interestingly, your good friend Seymour Myths, a scientist at the Research Institute of the Himalayas has shown that the asm gene is tightly linked to the ylw gene.
A. Please name the method you would use to clone asm (you do not need to provide the steps involved, 3 points).
B. You are so intrigued by Yeti genetics that you purify a protein called Fng that seems to regulate tooth development. You use the purified protein to immunize rabbits, produce a high affinity antibody that specifically recognizes Fng. Please briefly outline how you would clone the fng gene (i.e. the gene that encodes FNG). You do not need to give all the steps, just enough information to know the method you will use to find the clone (3 points).
C. Your research indicates that a mouse homolog to the yeti asm gene functions similarly. To further study asm function, you decide to mutate the mouse asm homolog. Assume that you have cloned the mouse asm gene, please describe how you would generate homozygous mouse asm mutants. Include a picture of the vector that you would use (8 points).
6.You are studying the genetics of the rare and ugly hairless llama when you notice that in some individuals the 10th chromosome is quite unusual. The normal chromosome is shown on the top and the unusual one is shown below.
A. Give the specific name of the chromosomal alteration that caused the strange chromosome (2 points).
B. Show the 2 chromosomes synapsed in meiosis (in a heterozygous individual). Include the genes (6 points).
C. Please show the products of meiosis in which a single crossing-over event has occurred between W and the centromere (4 points).
7. Strains heterozygous for each of five Drosophila mutations, a – e, and for each of five different deletions, 1 – 5 are generated. The table below shows whether such strains displayed wild type (+) or mutant (-) phenotypes. The figure illustrates the region deleted in each deletion strain (region deleted indicated by a bar) as determined by cytological examination of polytene chromosomes.
Assign each recessive mutation to the relevant region of the chromosome (6 points).
8.In two different interrupted mating experiments, you obtain the data shown below for the time of entry. All experiments were conducted using Hfr strains (Hfr1 and Hfr2) derived from the same original strain of E. coli.
Hfr1 Hfr2
jes6 minkev8 min
kat13 minpol13 min
pol14 minkat14 min
kev19 minjes21min
sha35 min mel65 min
mel50 minsha80 min
A. Draw a genetic map showing the location of and distances between each gene on the bacterial chromosome. Please include the Hfrs (8 points).
B. Two of the genes map very near one another (within a minute). Time of entry mapping does not provide a very accurate position for genes that are close to one another. Briefly describe how you could more accurately determine the relative positions of these two genes, including the steps involved. Assume the genes are required to synthesize a compound of the same name (eg. the kat gene would be required to synthesize Kat, polmakes Pol, etc., 4 points).
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