Problem Set 10, Fall 2015 Name: 8 points total 1. A Hfr strain possessing the markers his+ met+ tyr+ strs was mated with a F– strain possessing the markers his– met– tyr– strr. The time of entry for each marker is shown below. Donor Marker his+ met+ tyr+ Time (min) 21 12 46 a. Based on the results draw a map of the Hfr chromosome. Indicate the position of the F element, and the first marker to be transferred. b. On what type of plates were cells grown to determine the above information? 2. In three different interrupted mating experiments, you obtain the following data for the time of entry of the following genes: arg, met, leu, ser, gal, val, and phe. All of these experiments were conducted using Hfr strains (Hfr 1, Hfr 2, and Hfr3) derived from the same original strain of E. coli. Experiment 1 (Hfr 1) Met 10 min Val 25 min Leu 30 min Arg 40 min Ser 55 min Gal 60 min Experiment 2 (Hfr 2) Experiment 3 (Hfr 3) Gal 5 min Leu 5 min Ser 10 min Val 10 min Leu 35 min Met 25 min Val 40 min Phe 55 min Met 55 min Gal 75 min Phe 85 min Ser 80 min a. Determine the order of these genes on the bacterial chromosome and draw a single map showing the position of each of these genes on the bacterial chromosome. Based on the time intervals above, indicate the map distances between each gene, expressed in minutes. Also show the origin of transfer and direction of transfer for each Hfr. b. If the crosses were set up as described in class, what are the genotypes of the donor and recipient cells? 1 Problem Set 10, Fall 2015 8 points total Name: 3. In three different interrupted mating experiments, you obtain the data shown below for the time of entry. All experiments use Hfr strains derived from the same original parent strain. miy sow raj nub tod mic sha Hfr1 10 min 20 min 35 min 40 min 50 min 65 min 75 min Hfr2 sow 5 min miy 15 min chr 30 min sha 40 min mic 50 min tod 65 min nub 75 min Hfr3 5 min 20 min 30 min 35 min 50 min 60 min 75 min mic tod nub raj sow miy chr a. Show the genetic map for each of these genes on the circular chromosome. Indicate the location of each origin and the direction of transfer. Doesn’t need to be drawn to scale. b. What are the genotype of the donor and recipient strains? 4. The exotic tropical tree frog E. qinae normally has 13 pairs of chromsomes (i.e. 2n = 26). You find a number of unusual individuals with the chromosome content shown below. Please fill in the blanks for each of the variants in the table below: # chromosomes 25 ploidy of individual monoploid 28 tetraploid trisomic 2 Problem Set 10, Fall 2015 8 points total Name: 5. In an interrupted mating mapping experiment, you obtain the results shown in the graph below. The experiment was conducted as described in class. a. Show the genetic map for each of these genes on the circular chromosome. Indicate the location of the origin and the direction of transfer. Doesn’t need to be drawn to scale. b. What are the genotypes of the donor and recipient strains? donor: recipient: c. For each gene, the number of recombinants increases with time until they reach a maximum. Why does the number of recombinants for a given gene increase with time? d. Why does the number of recombinants reach a maximum? 6. Compare and contrast the three modes of bacterial DNA transfer. 3 Problem Set 10, Fall 2015 8 points total Name: 7. In a transduction mapping experiment, you get the following results. experiment 1 2 selected marker a+ b+ unselected markers 15% b+, 30% c+ 30% c+, 15% a+ a. Draw the relative position of a, b and c. b. a, b and c are enzymes required for the synthesis of A, B and C, respectively. An a mutant can’t grow without A in the media, etc. How are the above recombinants identified? 8. In studying a particular animal, you find that the fourth chromosome is unusual. The two copies of chromosome 4 are shown. The normal chromosome is shown on the top, and the unusual one is shown on the bottom. The position of seven genes is shown. a. What is the specific name of the chromosomal alteration that generated the abnormal chromosome? b. Show the two chromosomes synapsed in meiosis. Please include the genes. c. What effect will the rearrangement in the unusual chromosome have on recombination? Why? d. You find an individual homozygous for the abnormal chromosome (i.e. the bottom chromosome). Show it’s chromosomes synapsed in meiosis. Please include the genes. 4