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Mutations

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Hollywoods images of mutation

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Mutations Actual Mutations in fruit flies

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What is a mutation? A mutation is any change in a cells 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

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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 Edwards Syndrome Cri-du-Chat

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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)

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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?

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Gene Mutations

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

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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.

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

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

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

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

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

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

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Chromosomal Mutations Inversions reverse the direction of parts of chromosomes.

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

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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?

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