Introduction to Genetic Analysis 504

Introduction to - 44200_15_p481-520 1:07 PM Page 503 15.2 Changes in chromosome structure 503 = euchromatin = heterochromatin Normal chromosomes w1

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
binism), the homozygous deletion also will be viable. In- tragenic deletions can be distinguished from mutations caused by single nucleotide changes because genes with such deletions never revert to wild-type. For most of this section, we shall be dealing with multigenic deletions, in which several to many genes are missing. These have more severe consequences than do intragenic deletions. If such a deletion is made homozy- gous by inbreeding (that is, if both homologs have the same deletion), the combination is always lethal. This fact suggests that all regions of the chromosomes are essential for normal viability and that complete elimination of any segment from the genome is deleterious. Even an individ- ual organism heterozygous for a multigenic deletion— that is, having one normal homolog and one that carries the deletion—may not survive. Principally, this lethal outcome is due to disruption of normal gene balance. Al- ternatively, the deletion may “uncover” deleterious reces- sive alleles, allowing the single copies to be expressed.
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

Ask a homework question - tutors are online