Mutations Mutations Hollywoods images of mutation Mutations Actual

Mutations

Mutations • Hollywood’s images of mutation

Mutations • Actual Mutations in fruit flies

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 - cystic fibrosis a mutation in the protein that makes a type of ion channels in cell membrane - 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)

Critical Thinking • Will all mutations have a dramatic impact on an individual? How do you know? Which types of mutations do you think will have the greatest impact on an organism?

Gene Mutations

Kinds of Mutations • Substitutions usually affect no more than a single amino acid. • Also known as point mutations

Kinds of Mutations The effects of insertions or deletions are more dramatic. The addition or deletion of a nucleotide causes a shift in the grouping of codons. Changes like these are called frameshift mutations.

Kinds of Mutations • In an insertion, an extra base is inserted into a base sequence.

Kinds of Mutations • In a deletion, the loss of a single base is deleted and the reading frame is shifted.

Knowledge Check • What is a point mutation? Example? • What is a frameshift mutation? Example?

Chromosomal Mutations • Chromosomal mutations involve changes in the number or structure of chromosomes. • Chromosomal mutations include deletions, duplications, inversions, and translocations.

Chromosomal Mutations • Deletions involve the loss of all or part of a chromosome.

Chromosomal Mutations • Duplications produce extra copies of parts of a chromosome.

Chromosomal Mutations • Inversions reverse the direction of parts of chromosomes.

Chromosomal Mutations • Translocations occurs when part of one chromosome breaks off and attaches to another.

Critical Thinking • If Down Syndrome is characterized by having 3 copies of the 21 st chromosomes, would it be explained by a gene or chromosomal mutation? Which specific type of gene or chromosomal mutation? Why?

Significance of Mutations • Many mutations have little or no effect on gene expression. • Some mutations are the cause of genetic disorders. – Cancer – Down Syndrome