DNA (Gene) Mutations

What is a gene mutation?

Parts of DNA will have a base (or more) missing, added, or incorrectA mistake in the genetic codeWrong instructions wrong building materials

wrong structure.

How common are mutations?

Mutations occurs at a frequency of about 1 in every 1 billion base pairs

Everybody has about 6 mutations in each cell in their body!

If I have that many mutations, why don’t I look weird?

Mutations are not always seen. Every part of your DNA doesn’t make a protein or trait.Remember introns and exons?

Some genes are recessive and are therefore hidden, they can be passed to your kids but you don’t notice them.

The most common types of gene mutations are:

SubstitutionPoint mutations

Frame shift mutations (2 kinds)InsertionDeletion

DNA (Gene) Mutation

Normal DNA: CGA – TGC – ATC

Mutated DNA: CGA – TGC - TTC

What happened?

DNA (Gene) Mutation #1

Normal DNA: CGA – TGC – ATC

Mutated DNA: CGA – TGC - TTC

*Adenine was accidentally replaced with thymine

*What is this mutation called?

Substitution (point mutation)

Normal DNA: CGA – TGC – ATC

Amino acids: Ala -- Thr -- stop

Mutated DNA: CGA – TGC – TTC

Amino acids: Ala -- Thr -- Lys

What will happen to the amino acids? How many will be affected?

DNA (Gene) Mutation #2

Normal DNA: CGA – TGC – ATC

Mutated DNA: CGA – TAG – CAT - C

What happened?

DNA (Gene) Mutations

Normal DNA: CGA – TGC – ATC

Mutated DNA: CGA – TAG – CAT - C

*Adenine was inserted,causing the remaining DNA to shift to the right

*What is this mutation called?

Insertion

Normal DNA: CGA – TGC – ATC

Amino acids: Ala -- Thr -- stop

Mutated DNA: CGA – TAG – CAT – C

Amino acids: Ala -- Tyr -- Val -- …..

What will happen to the amino acids? How many will be affected?

DNA (Gene) Mutation #3

Normal DNA: CGA – TGC – ATC

Mutated DNA: CGA – TCA- TC

What happened?

DNA (Gene) Mutation

Normal DNA: CGA – TGC – ATC

Mutated DNA: CGA – TCA- TC

*Guanine was removed, causing the remaining DNA to shift to the left

*What is this mutation called?

Normal DNA: CGA – TGC – ATC

Amino acids: Ala -- Thr -- Stop

Mutated DNA: CGA – TCA- TC

Amino acids: Ala -- Ser --…….

Deletion

What will happen to the amino acids? How many will be affected?

• What causes mutations?Replication errorsTranscription errorsCell division errorsSpontaneous changesMutagens

•Mutagen? What’s that?•“Stuff” that causes mutations when a cell is exposed.

•Examples: UV light, Xrays, chemicals, etc.

What happens to someone with a mutation?That all depends…..

What kind of mutation it is.How many proteins are affected.Where in the polypeptide chain is the mutation.How many cells does it affect.

Mutations can be fatal, harmful, beneficial or nuetral.

• Which mutation would

organism?

have the least effect on an

•On intron sections of DNA•On unexpressed recessive traits.•Point mutations/substitutions

•Only affects 1 amino acid.

• Which mutation would

organism?

have the most effect on an

•Frame-shift mutations: •Deletions and insertions affect all amino acids after the mutation.

• When would a mutation

an organism?

have the most effect on

•During Meiosis•If gametes are produced with mutations, those mutations will be passed onto the offspring…….•Every cell of organism will contain mutation.

Repairing DNA

Enzymes proofread the DNA and replace incorrect nucleotides with correct nucleotides.

The greater the exposure to a mutagen such as UV light, the greater the chance that a mistake will not be corrected.