Page 33 - CB1.3 Genetic Varation sciPAD

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CB 1.3 GENETIC VARIATION
TRACKING GENES
Predicting Rat Fur Colour
From the previous exercise, recall that the colour of a rat’s coat is controlled by a gene. There are
two forms of this gene: the allele for black fur colour (B) is dominant over the allele for white fur
colour (b).
1. (a) Complete the Punnett square to show the possible results of a cross between a
homozygous dominant black male and a heterozygous black female.
(b) What is the probability (%) that an offspring will be:
(i) black? (ii) white?
2. (a) Complete the Punnett square to show the possible results of a cross between a
heterozygous black male and a heterozygous black female.
Black male
Alleles =
Black female
Alleles =
(b) What is the probability (expressed as a fraction) that an offspring will be:
(i) black? (ii) white?
(c) What is the probability (expressed as a fraction) that an offspring will be:
(i) homozygous dominant?
(ii) homozygous recessive?
(iii) heterozygous?
Black male
Alleles =
Black female
Alleles =
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