Mutations

What Are Mutations?

• Mutation: Changes in the nucleotide sequence of DNA

• Mutagen: A physical or chemical agent that changes DNA

• Mutation May occur in:1. somatic cells (body cells): will not be

passed to offspring2. gametes (eggs & sperm): can be

passed to offspring

Are Mutations Helpful or Harmful?

• Mutations happen regularly • Some mutations may improve an organism’s

survival (beneficial): It can be a source of genetic variability in a species

• Almost all mutations are neutral :They won’t affect the protein sequence

• Many mutations are repaired by enzymes• Chemicals & Radiation cause mutations:-e.g. Chemicals: Chlorine, Hydrogen peroxide

(H2O2), BenzeneRadiation: UV light, alpha ray, beta

ray gamma ray

Types of Mutations• There are 2 types of mutations:- Gene mutation: result from changes

in a single gene- Chromosome mutation: mutations

involve changes in whole chromosomes

Gene MutationThere are 2 types of gene mutations:1. Point mutations: Mutations that affect

one or more nucleotide- e.g. substitutions, insertions,

deletions2. Frameshift mutations: Mutations that

shift the reading frame of the genetic message

- e.g. Insertions, deletions

Point Mutation• Point Mutations – changes in one or

a few nucleotides– Substitution• THE FAT CAT ATE THE RAT• THE FAT HAT ATE THE RAT

– Insertion• THE FAT CAT ATE THE RAT• THE FAT CAT XLW ATE THE RAT

– Deletion• THE FAT CAT ATE THE RAT• THE FAT ATE THE RAT

Point Mutation Disease

• Sickle Cell Anemia is the result of one nucleotide substitution

• It Occurs in the hemoglobin (A protein in red blood cell) gene

Frameshift Mutation• Frameshift Mutations – shifts the

reading frame of the genetic message so that the protein may not be able to perform its function and it is often harmful– Insertion• THE FAT CAT ATE THE RAT• THE FAT HCA TAT ETH ERA T

– Deletion• THE FAT CAT ATE THE RAT• TEF ATC ATA TET GER AT

Chromosome Mutations• Chromosome mutations: Changes in

number and structure of entire chromosomes

• There are 5 types of chromosome mutations:

- Deletion- Duplication- Inversion- Translocation- Nondisjunction

Deletion and Duplication

• Deletion: Due to breakage, A piece of a chromosome is lost

• Duplication: Occurs when a gene sequence is repeated

Inversion• Inversion: Chromosome segment

breaks off and then flips around backwards and reattaches

Translocation• Translocation: Involves two

chromosomes that are not homologous, part of one chromosome is transferred to another chromosomes

Nondisjunction• Nondisjunction: Failure of

chromosomes to separate during meiosis, causes gamete to have too many or too few chromosomes