annotated-bio%20genetics%20lab%20worksheet%20week%205

.pdf

School

University Of Chicago *

*We aren’t endorsed by this school

Course

20186

Subject

Biology

Date

Dec 6, 2023

Type

pdf

Pages

Uploaded by MagistrateFang12431

Week 5 – Fly Mapping Lab Autumn 2022 1 Mapping a Mutation Mapping the cw mutation by recombination As you’ll recall from week 3, the overall goal of this lab is to map a historic trait (crumpled wing) to its molecular location on the chromosome. Before the quarter started, our fly technicians set up crosses with females of our mutant ( w- cw- f-) and males of one of four lines (mapB, mapC, mapD, or mapE), which carried the dominant wild-type allele for each of the three phenotypes (red/white eyes, flat/crumpled wing, straight/forked bristles). These map lines are actually in a w- background with P-element insertions that contain a w+ in known locations on the X chromosome. Those insertions may be to the left or right of the cw gene. When observed as a whole set of class data, we will be able to further refine the chromosomal region of the cw gene. Next week we will look at the progeny of the Deficiency and Duplication complementation crosses, which will refine the chromosomal region further by showing whether or not the cw gene is in a specifically defined region. In week 3, we observed the offspring of this cross and determined that the genes were X-linked and set up crosses between the F1 generation females and males. (w- cw- f-)/(w+ cw+ f+) X ( w- cw- f-)/Y Today we are calculating the recombination frequency between these genes. In the week 3 worksheet, you determined the 8 possible genotypes for each cross. This week you will sort through the progeny of the F1 cross and determine the recombination frequency between alleles. You will then use that data to determine the relative distance and order on the chromosome. While phenotypic markers are very useful in mapping genes , there are a limited number of markers available, which in turn limits the ability to map a gene to a narrow region of a chromosome. One improvement on mapping, developed by researchers in the fly community, was to randomly insert the w+ gene throughout the fly genome. Hundreds of these w+ insertion lines are available from the fly stock center and their physical location is known (a physical location is the nucleotide position along a chromosome). This creates a high density of visible markers that can be used to map genes to a narrow region of a chromosome. You are using some of these “fine-mapping” strains (MapB, MapC, MapD, and MapE) to narrow down the region where the cw mutation is located. You will be able to narrow down the cw location to less than a 1 Mb region of the X chromosome.

Week 5 – Fly Mapping Lab Autumn 2022 2 Sorting procedure 1. After anesthetizing the flies and placing all of the progeny on your CO2 pad, separate into red and white eyed flies (remember, red is w+, white is w- ) . After doing this, if you have a large number of progeny, it may be advisable to move one group to an empty vial while you’re scoring (determining the genotype of) the other group so you have more space, but this isn’t necessary. 2. Separate the w+ group by the crumpled wing phenotype (flat is cw+, crumpled is cw-) 3. Separate the cw+ group by forked (straight bristled is f+, forked is f-) 4. Count and record the number of male and female flies that are w+ cw+ f+. 5. Count and record the number of male and female flies that are w+ cw+ f-. 6. Those flies can now be placed in the morgue. 7. Return to the pile that is w+ cw- and separate by forked. 8. Count and record the number of male and female flies that are w+ cw- f+. 9. Count and record the number of male and female flies that are w+ cw- f-. 10. These flies can go to the morgue. 11. Return to the white eyed flies and separate by cw . 12. Separate the w- cw+ group by forked. 13. Count and record the number of male and female flies that are w- cw+ f+. 14. Count and record the number of male and female flies that are w- cw+ f-. 15. These flies can go to the morgue. 16. Return to the w- cw- flies and separate by forked. 17. Count and record the number of male and female flies that are w- cw- f+ . 18. Count and record the number of male and female flies that are w- cw- f-. 19. These flies can go to the morgue. Sort by eye color Sort by wing shape All progeny It is not necessary to sort males from females red white flat crumpled straight forked straight forked straight forked straight forked flat crumpled Sort by bristle type w+ cw+ f+ 1 w+ cw+ f- 2 w+ cw- f+ 3 w+ cw- f- 4 w- cw+ f+ 5 w- cw+ f- 6 w- cw- f+ 7 w- cw- f- 8 Record counts of each class in Table 1

Week 5 – Fly Mapping Lab Autumn 2022 3 Fly Worksheet (10 points) – Use this paper copy to record your data while scoring flies and then copy the data onto the class spreadsheet. (1 pt) Map strain you used (B, C, D, or E) _____B________ Parental Cross : w – cw- f- / w- cw- f- X map Table 1 Row Genotype Recombinant? (Y/N) # of flies (males and females)** 1 w+ cw+ f+ N 25 2 w+ cw+ f- Y 4 3 w+ cw- f+ Y 5 4 w+ cw- f- Y 1 5 w- cw+ f+ Y 1 6 w- cw+ f- Y 1 7 w- cw- f+ Y 7 8 w- cw- f- N 23 ** If you are uncertain of a phenotype, please ask for help . Don’t just guess! The distance calculations will be based on class data; mis-scoring on your part will affect other students. Now that you have this data, record it in the class spreadsheet. The spreadsheet will add up the numbers you entered and calculate the total number of flies. Record this value for your data TOTAL # of flies (recombinant and parental) 67 (CLASS TOTAL: 2413) To calculate the recombination frequencies, we need to look at each pair of alleles separately. To calculate the number of recombinant flies for each gene pair, FIRST identify which classes represent a crossover event between the listed genes. To calculate the recombination frequency, divide the number in column 3 but the total number of flies scored. (3pts) Alleles Row #’s Total # of recombinant flies Recombination frequency (%) Class Total # Class RF (%) Recombination distance (cM) Class Recombo distance (cM) w and cw 2+7 11 16.4% 340 14.1% 16.4 cM 14.1 cM w and f 3+6 6 9.0% 121 5.0% 9 cM 5 cM f and cw 4+5 2 3.0% 104 4.3% 3 cM 4.3 cM

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version