It is thought that in lab mice, hyperactive behaviour is caused by a single rece

Question

It is thought that in lab mice, hyperactive behaviour is caused by a single recessive allele of a single gene. In order to test this, crossings between heterozygous parents were conducted. Among 75 offspring, about how many individuals would you expect to be hyperactive if this prediction is true? After matings produced 75 offspring, 27 of them were observed to have hyperactive behavior; the other 48 offspring were behaviorally normal. Use a x^2 test (with 1 degree of freedom) to determine if these observed results match the expected results. Do the data suggest that hyperactivity is controlled by a single allele of a single gene.

Explanation / Answer

8. Consider normal allele is Domiant R and Hyperactive is Recessive r.

Heterozygous       Rr   *    Rr

            RR Rr      Rr       rr

RR and Rr are Normal.   only rr becomes hyperactive.

It gives 3: 1 ratio.   So out of 75 offspring 1/4 * 75 = 19 offspring becomes hyperactive.

9.

DF of 95% = 3.84

Cisquare value 4.77 > Table value 3.84 = Reject the H0

H0 - Hyperactive is not control by single allele of single gene.

So, this shows Hyperactive is control by single allele of single gene.

Observed Expected O-E (O-E)2 (O-E)2 / E Normal 48 3/4*75 = 57 -9 81 1.41 Hperactive 27 1/4 * 75 = 19 8 64 3.36 4.77

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