Running Head: GENETICS LAB REPORT

GENETICS LAB REPORT 2

Genetics Lab Practical ReportNameSubjectInstitutionDate

Part 1Using the lab animation, fill in the following data table to help you generate your hypothesis, outcomes, and analysis:Punnett SquareF1 P P

p Pp Pp p Pp Pp

All purple flowers 4 Pp.

F2 P p P PP Pp p Pp pp 3 Pp : 1 pp ratioPart 2Purpose To determine that the dominant allele is on the X chromosome when a red eye fruit fly female is cross with a white eye fruit fly male, and that it can be passed to successive generation.IntroductionThe X and Y chromosomes determine the sex of the fly. Similar to human, Drosophila fruit fly female have a genotype of XX and the male Drosophila have a genotype of XY. Male produces two types of sperm, one has an X chromosome and the other has a Y chromosome. The union of an egg with a sperm bearing an X chromosome produces XX female zygote and the union of egg with a Y chromosome produces XY male zygote. The fly expresses two different eye color. The alleles for both the red and white eye color are present on the X chromosome. The Y chromosome has no allele. Therefore, female have two alleles for this gene and males would have only one allele.HypothesisIf we cross the red eye female fly with a white eye male fly, all the F1 progeny would have red eyes, and the F2 generation would have 3 red eye fly to 1 white eye fly. This mean that the genes for red eye and white eye is located on the X chromosomes.MethodsTwo alleles are represent as W (red) and w (white). If we designate the X chromosomes as XW to indicate red eye and Xw to indicate white eye.

If we cross: P XWXW (Red female) X Xw Y (white male) Gametes XW Xw Y

F1 XW Xw (Red female) X XW Y (Red male)

Gametes 1/2 XW Xw 1/2 XW Y

F2 1/4 XWXW 1/4 Xw XW 1/4 XW Y 1/4 Xw Y Red female Red female Red male white male

ResultsThe genetic results are completely consistent with the known meiotic behavior of the X and Y chromosome. The experiment strongly supports the hypothesis that the dominant genes for red eye is located on the X chromosomes. In addition, it also support the notion that both red and white eye genes are located on the X chromosomes.

Discussion Since the female red eye fly has the genotype of XWXW and the white eye male has the genotype of XwY. When we crossed them, the gametes for both parents would carry independently assort randomly into of red female offsprings with the genotype XWXw and the other half of red male offspring with genotype XW Y. All the F1 progenies would have red eye color and half of the population are female and half are male. Because of independent assortment for the gametes in the F1 generations, the F2 generation would have 3 times as many red eye fly compared to 1 white eye fly. The ratio of red eye to white eye is 3:1. The number of female is equal to the number of male. This result supported the chromosome theory of heredity, which stated that genes and chromosome are in pair and alleles as well as pair of homologous chromosomes both segregate equally into gametes. Different genes behave independently as do different chromosome pairs. The parallel behavior of genes and chromosomes have led to the suggestion that genes are located on chromosomes. (1)

ReferenceAudesirk, T., Audesirk, G., & Byers, B. E. (2008). Biology: Life on Earth with physiology. Upper Saddle River, NJ: Prentice HallGriffiths et al. An introduction to Genetic Analysis. 5th Edition.