Page 46 - CB1.3 Genetic Varation sciPAD

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46 CB 1.3 GENETIC VARIATION
TRACKING GENES
Hints for answering
these questions
3. A rare genetic condition causes some cats to be born without the ability to produce
hair. Normal hair is produced by a dominant allele (H), while hairlessness is caused by
the recessive allele (h).
A haired cat A hairless cat
(a) Describe what is meant by the terms ‘dominant’ and ‘recessive’.




(b) After a cross between two cats it was found that half (50%) of the offspring had
normal hair and half (50%) of the offspring were hairless.
Describe the genotype and phenotype of the parents. In your answer you must:
•
define the terms ‘phenotype’ and ‘genotype’.
•
use a Punnett square to support your answer.








Parent 1: Genotype Phenotype
Parent 2: Genotype Phenotype
Use two separate
sentences to
define the terms
ensuring you use
the word ‘allele’ in
your answers.
Define ‘genotype’
ensuring you use the
word ‘alleles’.
Define ‘phenotype’
ensuring you use the
phenotypes given
in the question as
examples.
You will need
to deduce the
genotypes of the
parents. Try various
genotypes in
Punnett squares on
some scrap paper
to see which cross
would result in 50%
normal, 50% hairless.
Once you have
your answer, write
it neatly in the
Punnett square
provided.
State the parents’
genotype and
phenotype. Be
careful you don’t
mix them up.
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