Mutation & Genetic Variation

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

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

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!

II. CAUSES OF MUTATION:

1. _HEREDITY

2. _CARCINOGENS: chemicals, radiation, smoking, alcohol, etc.

3. _CHANCE: mistakes that happen during replication but are rare

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

2. _CROSSING OVER fails: incomplete separation of chromosomes leads to more or less chromosomes in new progeny (happens in meiosis)

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

Ex:

Normal: EAT THE CATMutation: EAT THE BAT

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

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