Mutations are changes or alterations in the DNA sequence that can disrupt genes and alter protein production. Mutations can occur during sexual or asexual reproduction and be inherited or non-inherited. Causes of mutation include heredity, carcinogens like chemicals and radiation, and chance mistakes during DNA replication. Major types of mutations include transposons that insert into chromosomes, crossover failures in meiosis, and single gene mutations like substitutions where nucleotides are replaced or deletions where nucleotides are removed. The results of mutations can include genetic variation and hereditary disorders or cancer depending on if they are inherited or non-inherited.

1. Mutation & Genetic Variation

2. 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

3. a. Mutation can involve the ENTIRE chromosome
or a SINGLE gene
b. May HELP, HARM, or have LITTLE to no effect on
future generations
o Changes may be SILENT or may cause
phenotypic changes

4. 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!

5. II. CAUSES OF MUTATION:
1. _HEREDITY
2. _CARCINOGENS: chemicals, radiation,
smoking, alcohol, etc.
3. _CHANCE: mistakes that happen during
replication but are rare

6. 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

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

8. 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 affected
ex: UCU and UCC both code for same amino acid
 If codon is a “stop” or different amino acid the
protein will be altered

10. Ex:
Normal: EAT THE CAT
Mutation: EAT THE BAT

11. b. DELETION:
 _ONE or MORE nucleotides may be DELETED
from the gene sequence
o More serious consequences than
substitutions
o The deletion of a single nucleotide cause
remaining nucleotide codons to be grouped
incorrectly

12. IV. RESULTS OF MUTATIONS
• CHANGES TO DNA CAN INCREASE CHANCES OF GENETIC
VARIATION THAT MAY OR MAY NOT BE HARMFUL
1. Hereditary disorders: inherited mutation
a. _SICKLE CELL ANEMIA
b. _PKU: phenylketonuria
c. _CYSTIC FIBROSIS
2. Cancer: non-inherited mutation