Mutations
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Mutations. Defined : one nucleotide is substituted for another Often repaired by spellchecker enzyme May lead to amino acid change See animation May not lead to any change (Silent Mutation) Ex: DNA “CCC” is mutated into “CC G ” Same amino acid is created (glycine). Gene: Point Mutations.

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Gene point mutations

Defined: one nucleotide is substituted for another

Often repaired by spellchecker enzyme

May lead to amino acid change

See animation

May not lead to any change (Silent Mutation)

Ex: DNA “CCC” is mutated into “CCG”

Same amino acid is created (glycine)

Gene: Point Mutations

T

A

C

A

G

T

G

G

T

C

A

A

A

DNA

U

G

U

C

A

C

A

C

A

G

U

U

U

mRNA

cysteine

glutamine

histidine

glutamine

phenylalanine

Amino acids


Gene frame shift mutation
Gene: Frame Shift Mutation

C

A

C

A

G

T

T

G

T

C

A

A

A

DNA

  • Defined: insertion/deletion of a nucleotide

  • Entire sequence of DNA/RNA after the mutation is shifted (see animation)

  • Much more serious to the structure/function of the final protein

    • mRNA sequence may have an early “stop codon”

    • mRNA sequence may have a late “stop codon”

G

U

G

U

C

A

A

C

A

G

U

U

U

mRNA

cysteine

glutamine

glutamine

phenylalanine

Amino acids

histidine

serine

leucine


Gene frame shift mutation1
Gene: Frame Shift Mutation

C

A

C

A

G

T

G

G

T

C

A

A

A

DNA

U

G

U

C

A

C

C

A

G

U

U

U

G

mRNA

histidine

glutamine

phenylalanine

cysteine

Amino acids

glutamine

proline

valine


Chromosome mutations
Chromosome Mutations

  • Translocation: Chromosome segments combine with nonhomologous chromosome

  • Many genes wind up on entirely different chromosomes

  • Gene cut apart

    • ½ on chr #5, ½ on chr #8



Impact on offspring
Impact on Offspring

  • Somatic cell mutations

    • Affect only the individual

    • Not passed on to future generations

    • Ex: Muscle cell mutation

  • Germ cell mutations

    • Germ cells = the diploid cells that undergo meiosis to make sperm & egg

    • May be passed to future generations


Mutation causes
Mutation Causes

  • Mutagen: agents in the environment that can change DNA

    • Speed up replication process

    • Break apart nucleotides

  • Ex: UV sunlight breaks hydrogen bond between thymine (T) and adenine (A)


  • Review
    Review

    • How are proteins affected if the DNA code is mutated?

      Example: ATTCGAGG is mutated to ATTCGTGG

    • What is the difference between point mutations, frame shift mutations, and translocation mutations?

    • When are mutations passed on to future generations?

    • What are germ cells?

    • What is a mutagen and how do they cause problems?


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