• What was your favorite thing about winter break?
• What is a karyotype?
• What is the purpose of a karyotype?
Chapter 12 Section 1
• 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
• 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
Male
Female
• 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)
• loss of a piece of chromosome
• Cri du chat
• Wolf-Hirschhorn syndrome
• 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: 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)