1. Mutations

2. Mutations mutation – a change in DNA sequence of bases
mutagen – agents that cause mutation, such as:
1) radiation
2) chemicals
3) viruses
4) natural causes (errors in replication)

3. Types of Mutations
I. Gene mutations – involve a single nucleotide or many nucleotides within one gene
1. frameshift mutations – loss or addition of
nucleotides that disrupts codon
2. point mutations – change in only one
nucleotide (substitution)

4. Types of Mutations II. Chromosomal mutations – involve entire
chromosomes or large pieces of chromosomes
A. Chromosome mutations involving pieces of
chromosomes:
1. deletion – a piece of a chromosome breaks off and is lost *most are lethal, killing the organism
2. duplication – part of a chromosome breaks off and is incorporated into its homologous chromosome

5. Types of Mutations 3. translocation – a chromosome part breaks
off and attaches to a different, non homologous chromosome
4. inversion – part of a chromosome breaks off,
turns around, & reattaches in the reverse
order

6. Types of Mutations Chromosome mutations involving whole chromosomes:
1. monosomy – missing one chromosome in
a pair
ex: XO (Turner Syndrome)
2. trisomy – having one extra chromosome
in a pair
ex: XXY (Klinefelter Syndrome) or XYY (Jacob Syndrome)
*all monosomies, trisomies are a result of nondisjunction

7. nondisjunction – failure of chromatid pairs to separate in anaphase
other monosomies/trisomies include:
Patau Syndrome (Trisomy 13)
Down Syndrome (Trisomy 21)
Edward Syndrome (Trisomy 18)
*Cri-du-chat – missing short arm of
chromosome #5 (deletion)

8. Karyotype
karyotype – procedure done to detect chromosome abnormalities
Steps: 1) tissue sample is taken
2) cells are grown in a flask for a few days
3) chemical is added to halt cell division
in metaphase
4) chromosomes are photographed and
enlarged
5) chromosomes are cut out & paired up
by size, shape, & centromere location
from largest to smallest