Chapter 16, Problem 28PDQ

Summary Introduction

To review:

The following:

(a) Neutral Polymorphism.

(b) The significance of the table in the context of examining a family or population for BRCA1 that predispose an individual to cancer.

(c) PM2 polymorphism results in a neutral missense mutation or a silent mutation.

(d) PM3 polymorphism results in a neutral missense mutation or a silent mutation.

Introduction:

Polymorphism occurs when locus of a gene is occupied by two or more alleles within a population. Types of polymorphisms are protein/enzyme polymorphisms and DNA (deoxyribonucleic acid) polymorphisms. DNA polymorphism is further segregated into neutral polymorphisms like Single nucleotide polymorphisms (SNPs), tandem repeat polymorphisms, structural polymorphisms (like deletions and inversions), and sequence polymorphisms. The table below shows the neutral polymorphisms in BRCA 1 gene:

Neutral Polymorphisms in BRCA1

Name	Codon Location	Base in codon+	Frequency in Control Chromosomes $\ast$
						A	G	T	C
PM3	1619	1	116	52	0	0
PM7	1190	2	109	53	0	0
PM1	317	2	152	10	0	0
PM6	878	2	0	0	100	55
PM2	1443	3	0	0	58	115

$\ast$ The number of chromosomes having the particular base at the indicated polymorphic site (A, G, T or C) is shown. + Position (1, 2, or 3) of the codon.