Huntington's disease is a genetic disorder - Edexcel - GCSE Biology - Question 4 - 2015 - Paper 1
Question 4
Huntington's disease is a genetic disorder.
The genetic diagram shows the inheritance of this disorder.
(a) (i) Use words or letters from the box to complete the f... show full transcript
Worked Solution & Example Answer:Huntington's disease is a genetic disorder - Edexcel - GCSE Biology - Question 4 - 2015 - Paper 1
Step 1
Huntington's disease is caused by a __________ allele.
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Answer
Huntington's disease is caused by a dominant allele.
Step 2
People with Huntington's disease can have the genotype Hh or __________.
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Answer
People with Huntington's disease can have the genotype Hh or HH.
Step 3
Complete the Punnett square to show the potential offspring of two parents heterozygous for Huntington's disease.
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Answer
The completed Punnett square is as follows:
H H
---------
H | HH | HH |
---------
h | Hh | Hh |
---------
This shows the potential genotypes of offspring being 50% HH and 50% Hh.
Step 4
State the probability that a child of two parents, heterozygous for Huntington's disease, will have the disorder.
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Answer
The probability that a child of two parents, heterozygous for Huntington's disease, will have the disorder is 75% or expressed as a fraction, rac{3}{4}.
