QuestionSBA
QuestionChoice
Huntington's disease is inherited in an autosomal dominant manner. This means that only one allele is required for someone to have the disease.

However, this question is asking how you can inherit a gene and not 'express' the gene. In other words not develop Huntington's disease.
10005875
e
Autosomal Dominant
QuestionChoice
Only one allele is required for the expression of the gene and development of a disease, examples include sickle cell anaemia and cystic fibrosis.

Huntington's disease is autosomal dominant and is more likely to show incomplete penetrance which is what this question is describing.
10005873
c
Autosomal Recessive
QuestionChoice
The mitochondrial DNA is only inherited from the mother. Therefore if the mother is affected by a condition 100% of the offspring will be affected. If the father is affected by the condition, no offspring will be affected.
10005874
d
Mitochondrial inheritance
QuestionChoice
This is where a patient can have the mutation but be asymptomatic for their entire life.

This is mostly associated with autosomal dominant conditions where even though they inherit the gene, the disease may not develop.

Another example is the inheritance of a BRCA mutation. This is a dominant inheritance but not all people will develop cancer.
10005871
a
Incomplete Penetrance
QuestionChoice
This is seen in trinucleotide repeat expansion disorders. Examples of these could be Huntington's disease and fragile x syndrome.

This refers to the disease severity and duration worsening with each generation. This is due to the expansion of the region of triplet base repeats.

Even though this can happen with Huntington's disease, this doctor is describing the possibility of offspring not expressing the gene at all. This is called incomplete penetrance.
10005872
b
Anticipation
Concept
Chapter
2693
4454
Penetrance
Topic
156
Medical Genetics
13721
A family is currently being counselled on their family history of Huntington's disease.

They are told that even if the gene is inherited doesn't mean they will go on to have the disease.

Which of the following describes this genetic phenomenon?
a