MUTATIONS Mutations can occur in DNA replication Protein Synthesis

MUTATIONS

Mutations can occur in•DNA replication•Protein Synthesis

Replication Error

• Nondisjunction: chromosomes fail to properly separate during anaphase

Whole chromosome mutations: May be diagnosed by a karyotype. Examples: Down’s syndrome (trisomy), Turner’s syndrome (X0), Klinefelter’s syndrome (XXY)

Mutations can affect a single base, several bases, or an entire chromosome.Example: translocation

Mutations can occur during replication or protein synthesis.

Mistakes could occur in either step

TRANSCRIPTION TRANSLATION

Occurs inside the nucleus when the DNA strands separate

Occurs in the cytoplasm at a ribosome

mRNA is made using the DNA template, then it leaves the nucleus via a nuclear pore

mRNA lined up at ribosome has “codon” (three base sequence) that the tRNA matches with an “anticodon”.

An

erro

r in

bas

e se

quen

ce in

DN

A o

r m

RN

A w

ould

res

ult i

n th

e w

rong

am

ino

acid

.

Frameshift Mutations:reading errors cause insertions or deletions

8

Making ProteinsMaking Proteins

DNADNA: TAC CGA TCG TGA ACT

mRNAmRNA: AUG GCU AGC ACU UGA

ProteinProtein: Met-Ala-Ser-Thr-Stop

TranscriptionTranscription

TranslationTranslation

9

Effect of Mutation Effect of Mutation on Proteinon Protein

DNADNA: TAC CGA TCG TGA ACT

mRNAmRNA: AUG GCU AGC ACU UGA

ProteinProtein: Met-Ala-Ser-Thr-Stop

TranscriptionTranscription

TranslationTranslation

C

G

Gly

Point mutation: a single base is incorrect.

Which amino acid would be delivered?

Would every single

base change

result in a different

amino acid?

Internal Mutations: a change in nucleotide sequence

• Occur during replication• Usually fatal to the cell, but vital for increasing genetic variety• Mutagen = agent that causes mutations (UV rays, chemicals, asbestos, cigarette smoke, etc.)

Types of Internal Mutations• Changes in nucleotide sequence• Are usually fatal to the cell, but vital for increasing

genetic variety• Types: