Genetics Study Material

Running head: GENETICS
1
Genetics
Name of the student
Name of university

GENETICS 2
Genetics
Part A
a) Data set for a cross between two breeding Drosophila strains that differ in traits
Wild type, female 1586
Wild type, males 807
Ruby eyes, males 770
Curved wings, females 517
Ruby eyes, curved wings, males 251
Curved wings, males 265
b) Genetic symbols
Wild type- recessive +/+
Ruby eyes- X-linked Female X+ X+, X+ XW; Male X+ Y
Curved wings- dominant- CC, Cc
c) Genetic hypothesis
The allele for curved wings is dominant while and the allele for ruby eyes is x linked and
dominant
Curved wings are dominant. This means that the gene will be expressed in both homozygous
state and heterozygous state.
P – CC(male) x Cc (female)
F1- CC, Cc, CC, Cc
F2- CC, Cc, Cc, cc
The F1 generation will all have curved wings. However, they will different genotypes. Some are
heterozygous while others are homozygous. The genotypic ration will be 1:1. The F2 generation
will have a larger propablty of having curved wings as compared to the probability of not having
curved wings. The phenotypic ration will be 3:1 and the genotypic ratio will be 1:2:1

GENETICS 3
Ruby eyes are sex linked genes. They are found of the X chromosomes. Females have two X
chromosomes while males have one X chromosome. The gene is dominant. It is expressed even
in homozygous state.
P- X+ X+ (female), XW Y (male)
F1- X+ XW, X+ Y, X+ XW , X+ Y
F2- X+ X+, X+ Y, X+ XW, XW Y
The F1 generation will consist of all offspring with red eyes. This is because they all posses an X
chromosomes. The genotypic ration for the F1 generation is 2:2. The females have the same
genotype while the males have the same genotype. The F2 generation will consist of females
with ruby eyes, one male with ruby eyes and one male with white eyes. The two female have the
same phenotype but different genotype. The genotypic ratio for F2 generation is 1:1:1:1
d) Breeding table to analyse the set hypothesis
X+ X X+ Y X+ XW XW Y
X+ X+, 1586 807 770 517
X+ Y 770 770 517
X+ XW 1586 517 251 265
XW Y 517 251 265
F1 generation phenotypic ratio = 1
Genotypic ration = 2:2
F2 generation phenotypic ratio = 3:1
Genotypic ration = 1:1:1:1
e) Chi square
The chi square helps to analyze the result got form the practical and the theoretical results. These
variation between is very useful in understanding genetics. The variation occurs as a result of
mutation in the sequences, evolution of genes and death of some organisms.
X2 = ∑ (O-E)2
E
= (770-251)2
251
= 1073.151394422311