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
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