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?
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