Mutations Hollywood’s images of mutation

MutationsEctrodactyly

Progeria

Hypertrichosis

Severe Combined Immunodeficiency Disorder (SCID)

Sickle Cell Anemia

Heterochromia iridium

What is a mutation? @A mutation is any change in a cell’s

DNA@ A mutation can occur in an individual

gene - results in a single changed protein - bacterial resistance to antibiotics is

an example of a beneficial gene mutation

What is a mutation continued

A mutation can occur in a chromosome - a chromosome contains many genes - chromosomal mutations affect many proteins Examples: Down Syndrome Edward’s Syndrome Cri-du-Chat

What Causes Mutations? Can be caused by mutagens- a physical or

chemical cause of mutation. Examples: UV light, radiation, drugs, and benzene.

Mutagens are often also carcinogens – anything that causes cancer

Can be natural, random events. - mutations occur in 1/100,000 DNA

replications Mutations do not have to be bad (evolution)

Gene Mutations1. Point Mutations

2. Frameshift Mutations

Point Mutations Substitution @A single nucleotide is altered@. Can

change one amino acid in a protein Milk – Mile GGACAATCA GGACCATCA proline -valine-serine proline-glycine-serine

Frameshift Mutations @A nucleotide is either inserted or

deleted from a gene.@ -all of the triplets from the point of

mutation onward will be changed

Frameshift Mutations Insertion An insertion occurs when a nucleotide is

added to a gene Example: A nucleotide is inserted

The fat cat ate the rat The faa tca tat eth era t -the extra nucleotide shifts all of the

triplets that follow

Frameshift Mutations Deletions A deletion occurs when a nucleotide is

removed from a gene.

Example: A nucleotide is removedThe fat cat ate the rat

Thf atc ata tet her at

Insertion GGACAATCA GCGACAATCA proline -valine-serine arginine-cysteine-stop

Deletion GGACAATCA GGAAATCA proline -valine-serine proline-leucine

Chromosomal Mutations

Chromosomal Mutations Chromosomal mutations involve changes in

the number or structure of chromosomes.

Chromosomal Mutations Deletion involves the loss of all or part

of a chromosome.

Chromosomal Mutations Duplication produces an extra copy of

all or part of a chromosome.

Chromosomal Mutations Inversion reverses the direction of

parts of a chromosome.

Chromosomal Mutations Translocation occurs when part of one

chromosome breaks off and attaches to another.

Harmful and Helpful Mutations

The effects of mutations on genes vary widely. Some have little or no effect; and some produce beneficial variations. Some negatively disrupt gene function.

@However, without mutations, organisms cannot evolve@

Mutations are the source of genetic variability in a species.

Harmful Effects Some of the most harmful mutations

are those that dramatically change protein structure or gene activity causing genetic disorders.

Some cancers, for example, are the product of mutations that cause the uncontrolled growth of cells.

http://www.pbs.org/wgbh/nova/cancer/grow_flash.html

Harmful Effects Sickle cell disease is a

disorder associated with changes in the shape of red blood cells. Normal red blood cells are round. Sickle cells appear long and pointed.

@Sickle cell disease is caused by a point mutation in one of the polypeptides found in hemoglobin@. (the blood’s principal oxygen-carrying protein)

Beneficial Effects Mutations often produce proteins with new or altered functions that can be useful to organisms in different or changing environments.

For example, mutations have helped many insects resist chemical pesticides.

Beneficial Effects Plant and animal breeders often make

use of “good” mutations.

The condition in which an organism has extra sets of chromosomes is called polyploidy.