You are studying ear length in rabbits. There are two phenotypes, long and short
ID: 17685 • Letter: Y
Question
You are studying ear length in rabbits. There are two phenotypes, long and short ears, which are controlled by the E and e alleles, respectively. Long ears are dominant over short ears. You hypothesize that the trait is following simple Mendelian inheritance. To test this, you cross a true-breeding long eared rabbit with a true-breeding short eared rabbit to produce the F1 heterozygotes. You then cross the F1 offspring to produce the F2 rabbits. Examining 200 rabbits, you note that 130 rabbits have long ears and 70 have short ears. Does the data support your hypothesis? Support your answer with a chi-squared analysis.Explanation / Answer
phenotypes,
long and short ears, which are controlled by the E and e alleles, respectively.
Long ears are dominant over short ears.
true-breeding long eared rabbit with a true-breeding short eared rabbit to produce the F1 heterozygotes.
long eared rabbit EE X ee short eared
Ee--- long eared rabbit------------- F1 offspring
then cross the F1 offspring to produce the F2 rabbits.
Ee--- long eared rabbit x Ee--- long eared rabbit
E
e
E
Ee
long eared rabbit
Ee
long eared rabbit
e
Ee-
long eared rabbit
ee
short eared
phenotype ratio is -------------3:1
Ee- long eared rabbit---------3/4;
short eared-ee------------1/4
Examining 200 rabbits, you note that 130 rabbits have long ears and 70 have short ears.
GENOTYPE phenotype
OBSERVED
EXPECTED
O-E
(O-E)^2
(O-E)^2/E
EE
long eared rabbit
homozygotes
AND Ee
long eared rabbit
heterozygotes zygotes
130
150
-20
400
2.6
ee
short eared rabbit
homozygotes
70
50
20
400
2.6
TOTAL
200
200
5.2
CHI-SUARE VALUE= (O-E)^2/E
NULL hypothesis: THE OFFSPRING ARE ACCORDING TO HARDY WEINBERG LAW
ALTERNATIVE hypothesis: THE OFFSPRING ARE NOT ACCORODING TO HARDY WEINBERG LAW
CALCULATE VALUE IS MORE THAN TABLE TABLE AT 5% LEVEL OF SIGNIFICANCE , HENCE REJECT THE NULL hypothesis AND ACEPT
ALTERNATIVE hypothesis.
E
e
E
Ee
long eared rabbit
Ee
long eared rabbit
e
Ee-
long eared rabbit
ee
short eared
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