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Question 574

Genetics → General

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Type SSBA

UUID bfc86bba-589a-4ccb-b3b3-5b20e70048de

Classification

Speciality

Obstetrics and Gynaecology

Group

Basic

Title

Genetics

Topic

General

Subtopic 1

Principles of Inheritance

Subtopic 2

Autosomal Recessive Inheritance

Subtopic 3

Inherited Gene Copies

Question Type

SBA

Question

SSBA

Question Header

Question Stem

A child is being assessed for a condition that follows autosomal recessive inheritance. A mutated copy of the relevant gene has been identified in the child's DNA and traced to the mother. Several RNA transcripts from that same maternal gene copy are also detected. The child's paternally inherited copy has not yet been characterised. An observer incorrectly treats the multiple transcripts as evidence that the child has inherited two mutated gene copies.

Options

A The child's paternally inherited copy of the same gene is also mutated

B The child's maternally inherited copy produces additional RNA transcripts

C The father has a mutated copy of the gene, without establishing which copy the child inherited

D The mother has two mutated copies of the gene, without characterising the child's paternal copy

E The mother has a mutation in her mitochondrial DNA

Explanation

Autosomal recessive inheritance requires the child to inherit two mutated gene copies, one from each parent. Multiple RNA transcripts can be copies made from the same DNA sequence; their number does not establish a second inherited gene copy. The unresolved requirement is therefore a mutated paternal copy in the child, rather than further evidence concerning the already identified maternal copy or a parent's genotype alone.

Option Validity

B) Additional transcription from the same maternal DNA copy does not show that a mutated copy was inherited from the father.

C) A mutated paternal gene copy must be shown to have been inherited by the child; its presence in the father alone leaves that requirement unresolved.

D) More information about the mother's gene copies does not establish the state of the child's paternally inherited copy.

E) Mitochondrial DNA is maternally inherited and does not establish the required mutated paternal copy of the autosomal gene.

Source & metrics

Authored Difficulty

5.00

Evaluation Score

—

Destination

Site

Source

Saxena - MRCOG-1 Basic Sciences - Genetics

Source Section

Chapter 8 — Genetics; Principles of Inheritance; Transcription; Mitochondrial DNA

Source Locator

Printed pages 255–256 and 258

Updated

2026-10-06 01:57:35

Difficulty Factor

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