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 21st 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