6.4 Cell Division: Karyotypes and Mutations Chapter 12 Section 1
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?