Mutations

Mutations

• Change / alteration to the DNA of an organism• They may be good, bad or have no effect• A plant that can better tolerate the cold (GOOD)• A change that causes some syndrome or illness (BAD)• A change that we never see or notice (NONE)

• A driving force behind evolution• A plant that can better tolerate the cold (GOOD)

Causes of mutations

• Naturally occurring (they just happen) 2/3 of all cancers

• Mutagen – something in the environment that causes a change

• Examples: radiation (x-rays), pollution and toxic chemicals (Love Canal), smoking, diet, etc….

Types of mutations

• Genetic – causes a change in the gene• May only effect one gene• Change in the base (A,T, C, G)

• Chromosomal – causes a change in a chromosome or segments of a chromosome

Genetic mutations

• 1.Deletions: remove a base from the sequence • ATCCGACAG (codons are in groups of 3)• ATCGACAG

• 2.Insertions: a base is added to the sequence• ATCCGACAG• ATTCCGACAG

• These are both called frameshift mutations they cause a change in how the sequence is read

Types of genetic mutations

• 3. Substitutions: a base is changed (one is substituted for another)

• AGGCAA• AGCCAA• A substitution may not cause any change in

the amino acid

Examples of genetic mutations

• Color blindness – x chromosome (sex linked)• Hemophilia – x chromosome (sex linked)

(free bleeding)• Sickle cell – chromosome 11 (causes a change

in the shape of red blood cells)

Chromosomal mutations

• Deletions – chromosome is deleted• Duplication – chromosome is duplicated• Inversion – chromosome is inverted• Translocation – piece of a chromosome is

moved to another chromosome (not homologous)

• Non-disjunction – chromosomes don’t separate properly

Examples of chromosomal mutations

• Downs syndrome – trisomy 21 (3 copies of the 21 chromosome total of 47 chromosomes)

• Turner’s syndrome – x or piece of the x chromosome is missing (45 chromosomes)

• Klinefelter’s syndrome – xxy (47 chromosomes an extra x chromosome)