6.4 Cell Division: Karyotypes and MutationsChapter 12 Section 1

Chromosome Review• All of an organism’s DNA can be packaged

into chromosomes• Humans - 23 pairs or 46 total chromosomes

• Each pair of chromosomes contain genes with 2 alleles (1 from each parent)

• Chromosome Numbers• 1-22 autosomes• Sex chromosomes “#23”• XX – Female• XY - Male

Karyotypes

• A karyotype is a picture of all chromosomes in a cell, for one organism

• Karyotypes can show:• changes in chromosomes• deletion of part or loss of a chromosome• extra chromosomes

Identifying Gender by Karyotype

Male Female

Mutation• A change in a genetic trait• 1) chromosomal • 2) gene mutation

• Germ cell (gametes) or somatic cell (body)• Germ cell mutations can be inherited and somatic cell

mutations result in cancers

• Can be lethal (even before birth)

Chromosomal Mutations

Deletion• loss of a piece of chromosome• Cri du chat • Wolf-Hirschhorn syndrome

Inversion & Translocation• Inversion: chromosome breaks off and reattaches

in reverse• Translocation: piece breaks off and attaches to

another

• * No problems in an individual since all genes are intact but there are problems with crossing over during meiosis

Nondisjunction• Nondisjunction: failure of a chromosome to

separate from its homologous chromosome• Trisomy - one too many chromosomes (2n=47)• EX Down Syndrome, Kleinfelter’s Syndrome (XXY)

• Monosomy - only one of a homologous pair (2n=45)• EX. Turner Syndrome (X)

Can you find what is wrong?