Download Karyotypes and Mutations

• When does crossing over occur? When does
independent assortment occur?
• Describe the cells that result at the end of
meiosis
• TAKE OUT YOUR MEIOSIS vs MITOSIS AND
MITOSIS FOLD TO BE STAMPED
Chapter 12 Section 1
• All of an organism’s DNA can be packaged into
chromosomes
• Humans - 23 pairs or 46 total chromosomes
• 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 (#5)
•Wolf-Hirschhorn syndrome (#4)
• 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)