15.4 Changes in Chromosome # & structure.notebook

1

February 16, 2017

15.4 Changes in chromosome # & structureA. Changes in the # of chromsomes

1. Polyploidy a. 3 or more sets of chromosomes in an organismb. caused by nondisjunction (Meiosis I & II)c. not common in animals, can cause speciation in plants

i. plants: Diploid egg of one species joins with diploid pollen of another species

2. Aneuploidy a. +/- than the normal # of chromosomes.

i. monosomy (2n-1) & trisomy (2n+1) ii. Caused by nondisjunction

http://glencoe.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::550::400::/sites/dl/free/0078695104/383925/Chapter11_NGS_VisualizingNondisjunction_10_10_06.swf::Visualizing%20Nondisjunction

15.4 Changes in Chromosome # & structure.notebook

2

February 16, 2017

3. Changes in sex Chromosome #a. inheriting too many X's or Y'sb. due to non-disjunction of sex chromosomesc. examples

i. Turner syndrome (XO) = femaleii. Klinefelter (XXY) = male

- Presence of Y determines maleness- SRY gene on short arm of Y chromosome

15.4 Changes in Chromosome # & structure.notebook

3

February 16, 2017

B. Changes in Chromosome Structure

15.4 Changes in Chromosome # & structure.notebook

4

February 16, 2017

Tan = euchromatic (active) portion of the non-recombining region of the Y

Black = heterochromatic (inactive) portion of the SRY

Gray = centromere

Red =pseudoautosomal (homologous regions between X & Y chromosomes) regions.

Genes on the right of the map have active X-chromosome homologues. Genes on left of the map lack known X homologues.

Genes in red are widely expressed housekeeping genes. Carry out basic cell functions

Genes in black are expressed in the testis only.

With the exception of the SRY gene, all the testis-specific Y genes are multicopy.

SRY gene:- sex determining region.-turns on production of testosterone- if it's turned on = male, if not = female

SRY gene on the Y chromosome