MCQs on Single-gene inheritance

Single gene-pair inheritance occurs when a trait is linked to one gene-pair that consists of two alleles. This is also referred to as Mendelian inheritance. An allele is one part of the gene-pair. One allele is inherited from the father, and one is inherited from the mother.

Question 1

Male to male transmission is a key feature of which pattern of inheritance?
Your answer:
c) X-linked dominant
Correct answer:
a) Autosomal dominant
A man does not transmit his X chromosome to his sons so that an X-linked disorder cannot be passed from father to son. Usually autosomal recessive disorders affect members of only one generation.
Page reference: 71 and 77

Question 2

Consanguinity shows a strong association with which pattern of inheritance?
Your answer:
b) Autosomal recessive
Consanguinity provides an opportunity for a rare recessive allele to ‘meet up with itself’.
Page reference: 74

Question 3

Which of the following disorders does not show X-linked inheritance?
Your answer:
b) Tay-Sachs disease
Tay-Sachs disease shows autosomal recessive inheritance.
Page reference: 78

Question 4

Which of the following would result in Angelman syndrome?
Your answer:
c) Deletion in the paternally derived chromosome 15
Correct answer:
b) Paternal UPD 15
Angelman syndrome is caused by loss of a functioning maternally derived chromosome 15. The other listed mechanisms will all cause the Prader-Willi syndrome.
Page reference: 86

Question 5

Leber’s hereditary optic atrophy is caused by a mutation in:
Your answer:
a) chromosome 12.
Correct answer:
d) mitochondrial DNA.
This condition shows mitochondrial inheritance as discussed in Box 4.3.
Page reference: 87

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