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.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Huntington's disease is caused by a dominant allele.
Step 2
People with Huntington's disease can have the genotype Hh or __________.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
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.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The Punnett square for heterozygous parents (Hh) is as follows:
| H | h |
-------------------
H | HH | Hh |
-------------------
h | Hh | hh |
This shows that the potential offspring genotypes are HH (homozygous dominant), Hh (heterozygous), and hh (homozygous recessive).
Step 4
State the probability that a child of two parents, heterozygous for Huntington's disease, will have the disease.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The probability that a child of two parents, heterozygous for Huntington's disease (Hh), will have the disease is 75% or 3:1.
