SBA — Single Best Answer · Review
Question 577
Genetics → General
Classification
Question
SSBAQuestion Header
Which pair belongs entirely in the autosomal recessive category?
Question Stem
A genetics teaching chart groups named disorders by their usual inheritance pattern. Two examples are required for its autosomal recessive category.
Options
A
Cystic fibrosis and neurofibromatosis
B
Wilson's disease and Christmas disease
C
Gaucher's disease and colour blindness
D
Cystic fibrosis and Wilson's disease
E
Neurofibromatosis and Christmas disease
Explanation
Cystic fibrosis and Wilson's disease both follow autosomal recessive inheritance. In contrast, neurofibromatosis follows an autosomal dominant pattern, while Christmas disease and the usual inherited colour blindness pattern are X-linked. The pair must therefore be selected by the pattern shared by both disorders, not by one correctly placed member.
Option Validity
A) Cystic fibrosis is autosomal recessive, but neurofibromatosis is autosomal dominant.
B) Wilson's disease is autosomal recessive, but Christmas disease is X-linked.
C) Gaucher's disease is autosomal recessive, but the colour blindness pattern considered here is X-linked.
E) Neurofibromatosis is autosomal dominant and Christmas disease is X-linked; neither supplies the requested autosomal recessive pair.
Further Reading
Saxena R. Textbook for MRCOG-1: Basic Sciences in Obstetrics and Gynaecology. 1st ed. Jaypee Brothers Medical Publishers; 2016. Chapter 8: Genetics — Principles of Inheritance; Autosomal Recessive Pattern of Inheritance; Table 8.1. Printed page 258.