8.7 – mutations. key concept mutations are changes in dna that may or may not affect phenotype....

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8.7 – 8.7 – Mutations Mutations

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Page 1: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

8.7 – Mutations8.7 – Mutations

Page 2: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Key ConceptMutations are changes in DNA that may or may

not affect phenotype.

mutatedbase

Page 3: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

What Are Mutations?What Are Mutations?

Changes in the nucleotide sequence of DNA

May occur in somatic cells (aren’t passed to offspring)

May occur in gametes (eggs & sperm) and be passed to offspring

Page 4: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Are Mutations Helpful or Harmful?

Mutations happen regularly

Almost all mutations are neutral

Chemicals & UV radiation cause mutationsMutagens are anything in the environment that can cause mutations

Many mutations are repaired by enzymes

Page 5: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Are Mutations Helpful or Harmful?

Some types of skin cancers and leukemia result from somatic mutations

Some mutations may improve an organism’s survival (beneficial)

Page 6: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Types of Mutations

Page 7: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Chromosome Mutations

May Involve:Changing the structure of a chromosome

Loss or gain of part of the chromosome

Page 8: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Chromosome Mutations

Five types exist:DeletionInversionTranslocationNondisjunctionDuplication

Page 9: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Deletion

Due to breakage

A piece of a chromosome is lost

Page 10: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Inversion

Chromosome segment breaks off

Segment flips around backwards

Segment reattaches

Page 11: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Duplication

Occurs when a gene sequence is repeated

Page 12: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

TranslocationInvolves two chromosomes that aren‘t homologous

Part of one chromosome is transferred to another chromosome

Page 13: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base
Page 14: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Nondisjunction

Failure of chromosomes to separate during meiosis

Causes gamete to have too many or too few chromosomes

Page 15: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

NondisjunctionCan cause “Trisomy” (three copies of

the same chromosome in an egg or sperm)Trisomy 21 (Down syndrome)

Page 16: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Chromosome Mutation Animation

Page 17: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base
Page 18: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Gene MutationsChange in the nucleotide sequence of a gene

May only involve a single nucleotide

May be due to copying errors, chemicals, viruses, etc.

Page 19: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Types of Gene Mutations

Include:Point MutationsSubstitutionsInsertionsDeletionsInversionsFrameshift

Similar to the chromosomal versions of these mutations

Page 20: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Point Mutation

Change of a single nucleotide

Includes the deletion, insertion, or substitution of ONE nucleotide in a gene

Page 21: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Point Mutation

Sickle Cell disease is the result of one nucleotide substitution

Occurs in the hemoglobin gene

Page 22: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Nonsense MutationType of point mutation

Results in a premature stop codon and usually a nonfunctional protein

Page 23: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Frameshift Mutation

Inserting or deleting one or more nucleotides

Changes the “reading frame” like changing a sentence

Proteins built incorrectly

Page 24: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Frameshift Mutation

Original:The fat cat ate the wee rat.

Frame Shift (“a” added): The fat caa tat eth ewe era t.

Page 25: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Amino Acid Sequence Changed

Page 26: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Gene Mutation Animation

Page 27: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Silent Mutations

Some mutations have no effect and are called “silent”Example:GUC changed to

GUGBoth code for the

amino acidvaline

This would not affect the proteinbeing made in any way

Page 28: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Mutations may or may not affect phenotype.Chromosomal mutations tend to have a big

effect.

Some gene mutations change phenotype by:causing a premature stop codon.causing a change in protein shape or the active

site.causing a change in gene regulation.

Page 29: 8.7 – Mutations. Key Concept  Mutations are changes in DNA that may or may not affect phenotype. mutated base

Some gene mutations do not affect phenotype.

A mutation may be silent because….

– It occurs in a non-coding region.

– It may not affect protein folding or the active site.