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Experiment 5
Locating Genes on Chromosomes
James Chung
Due: August 14, 2007
Biol 340 — Summer
Purpose:
The purpose of this experiment is to determine on which specific linkage group an assigned recessive mutation is located (Jefferson, 2004). This example will familiarize us with crossing over and the genotype of our experimental subject — drosophila.
Materials and Methods:
During week four of lab, each group should have made a P1 cross and examined the resulting progenies. However, the lab flies died before the class could perform the experiment, so it we decided to use fly lab.
In fly lab a female expressing vestigial wings was crossed with a male expressing curly wings, plum eyes, stubby bristles and dichaete wings. Each of the male mutations is lethal when homozygous and male drosophila DNA does not cross over during meiosis.
In flylab, the parentals were crossed and then the F1 was examined for the appearance of recessive traits, which would reveal sex linkage. Afterwards, the student made several test crosses to check for linkage. Each testcross was done excluding males that would carry genotypes that would be affected by epistasis. If the crosses were affected by epistasis the resulting ratios and progeny counts would be affected. Once the testcrosses were completed, each student mapped out the genes loci.
Results:
Flylab Lab Notes for james chung
Results of Cross #1
Parents
(Female: VG) x (Male: SB;ST;CY;D)
Offspring
Phenotype Number Proportion Ratio
Female: SB;ST 1253 0.1249 1.029
Male: SB;ST 1279 0.1275 1.050
Female: SB;CY 1242 0.1238 1.020
Male: SB;CY 1243 0.1239 1.021
Female: ST;D 1218 0.1214 1.000
Male: ST;D 1261 0.1257 1.035
Female: CY;D 1291 0.1287 1.060
Male: CY;D 1247 0.1243 1.024
Total 10034
F1
Results of Cross #1
Ignoring Sex
Parents
(Female: VG) x (Male: SB;ST;CY;D)
Offspring
Phenotype Number Proportion Ratio
SB;ST 2532 0.2523 1.021
SB;CY 2485 0.2477 1.002
ST;D 2479 0.2471 1.000
CY;D 2538 0.2529 1.024
Total 10034
F1 ignoring sex
Results of Cross #2
Parents
(Female: VG) x (Male: SB;ST)
Offspring
Phenotype Number Proportion Ratio
Female: ST 1249 0.1261 1.070
Male: ST 1292 0.1304 1.107
Female: SB;ST 1167 0.1178 1.000
Male: SB;ST 1224 0.1236 1.049
Female: VG 1229 0.1241 1.053
Male: VG 1252 0.1264 1.073
Female: SB;VG 1214 0.1226 1.040
Male: SB;VG 1278 0.1290 1.095
Total