Download - Mutation notes
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Mutation & Genetic Variation
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I. MUTATION & GENETIC VARIATION
1. Mutation: a CHANGE or alteration of the DNA sequence that can cause a disruption of a gene and in turn alter the production of a protein
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a. Mutation can involve the ENTIRE chromosome or a SINGLE gene
b. May HELP, HARM, or have LITTLE to no effect on future generationso Changes may be SILENT or may cause
phenotypic changes
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c. Can occur during SEXUAL and ASEXUAL reproduction
• _INHERITED mutation: occur in gametes and can be passed down to offspring cells– Happens during meiosis
• _NONINHERITED mutation: occur in somatic cells which can alter the future new cells– Happens during mitosis!
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II. CAUSES OF MUTATION:
1. _HEREDITY
2. _CARCINOGENS: chemicals, radiation, smoking, alcohol, etc.
3. _CHANCE: mistakes that happen during replication but are rare
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III. MAJOR EXAMPLES THAT CAUSE MUTATIONS:
1. _JUMPING GENES: a TRANSPOSON or segment of DNA that can insert itself into different positions along a chromosome
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2. _CROSSING OVER fails: incomplete separation of chromosomes leads to more or less chromosomes in new progeny (happens in meiosis)
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3. SINGLE GENE MUTATIONS
a. SUBSTITUTION: ONE or MORE nucleotides are REPLACED by a different nucleotide in the gene sequence ex: AGA copied as AGG Results in a NEW CODON (mRNA) If codon is the same as the original, the
protein will not be affectedex: UCU and UCC both code for same
amino acid
If codon is a “stop” or different amino acid the protein will be altered
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Ex:
Normal: EAT THE CATMutation: EAT THE BAT
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b. DELETION: _ONE or MORE nucleotides may be DELETED
from the gene sequenceoMore serious consequences than
substitutionsoThe deletion of a single nucleotide cause
remaining nucleotide codons to be grouped incorrectly
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IV. RESULTS OF MUTATIONS• CHANGES TO DNA CAN INCREASE CHANCES OF GENETIC
VARIATION THAT MAY OR MAY NOT BE HARMFUL
1. Hereditary disorders: inherited mutationa. _SICKLE CELL ANEMIAb. _PKU: phenylketonuriac. _CYSTIC FIBROSIS
2. Cancer: non-inherited mutation