Mutation: Any change or error in DNA
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Transcript of Mutation: Any change or error in DNA
Mutation:Any change or error in DNA
• If mutations occur in reproductive cells, the altered gene will become part of the genetic makeup of the offspring.
• If mutations occur in somatic cells (body cells), the mutation will not be passed on.
• However, problems may arise for the individual.
Mutagen: any agent that causes a change in DNA
• Radiation such as ultraviolet light, X rays, or radioactivity
• Chemicals including asbestos, cyanide, formaldehyde, tobacco
I. Point Mutation
• A change in a single base pair in DNA
mutatedbase
A. Substitution: one base is changed to another
Substitution mutation
GGTCACCTCACGCCA
↓
CCAGUGGAGUGCGGU
↓
Pro-Arg-Glu-Cys-Gly
Substitutions will only affect a single codonTheir effects may not be serious unless they affect an amino acid that is essential for the structure and function of the finished protein molecule (e.g. sickle cell anemia)
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
Substitution mutation causing sickle cell anemia
B. Inversion: two bases switch position
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
Inversion mutation
GGTCCTCTCACGCCA
↓
CCAGGAGAGUGCGGU
↓
Pro-Gly-Glu-Cys-Gly
Inversion mutations, also, only affect a small part of the gene
C. Deletion: one base is deleted
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
Deletion mutation
GGTC/CCTCACGCCA
↓
CCAGGGAGUGCGGU
↓
Pro-Gly-Ser-Ala-
A frame shift mutation, because it shifts the reading of codons by one base
D. Insertion: one base is added
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
Insertion mutation
GGTCTGCCTCACGCCA
↓
CCAGACGGAGUGCGGU
↓
Pro-Asp-Gly-Val-Arg
A frame shift mutation, because it shifts the reading of codons by one base
Question:
Which type of mutation would have a greater effect on the sequence of amino acids in a protein, a substitution mutation or a deletion mutation? Explain
II. Chromosomal Mutations• Occur during mitosis or meiosis; parts of
chromosomes break off and are lost or rejoin incorrectly.
• Pictures p. 321
A. Deletion: Part of a chromosome is left out
B. Insertion: part of a chromatid breaks off and attaches to its sister chromatid.
(this can also be called a duplication)
C. Inversion: part of a chromosome breaks off and is reinserted backwards
D. Translocation: part of one chromosome breaks off and is added to a different chromosome