Mutations

What is a Mutation?

Any change in the DNA sequence of bases,  which leads to a change in the mRNA created in transcription and the protein created in translation to possibly change the traits expressed

Internal Factors

• DNA is not accurately copied in replication. 

• Naturally Occuring (not always repaired by Polymerase)

• Strand breaks during cell division accidentally (repaired incorrectly)

External Factors

DNA is damaged by factors that cause the DNA to break (ex: carcinogens)

What do Gene Level (small-scale) mutations do? ? ? ? ? ? ? ? ? ?

affect DNA at the molecular level by changing the normal sequence of nucleotide base pairs. 

When do small scale mutations occur?

Occurs during the process of DNA replication

What are some examples of Gene-level mutations?

Substitutions, Deletions, Insertions

What do Chromosomal (large-scale) mutations do?

affect entire portions of the chromosome. Entire genes or sets of genes are altered rather than only single nucleotides of the DNA.

Mutations involving multiple chromosomes are likely to occur in

mitosis / meiosis (gametes)

Movement of chromosomes causes

breaks

Substitutions/point mutations occur when

nucleotide is replaced with a different nucleotide in the DNA sequence.

3 categories of subsitutions

1. Silent = no change in amino acid

2. Missense = changes an amino acid to another amino acid.

3. Nonsense = changes an amino acid to a STOP codon, resulting in premature termination of translation.

Insertions are the addition

of a nucleotide to the DNA sequence.

Deletions are the removal of a nucleotide

from the DNA sequence.

What do insertions and deletions result from?

Usually results from a “slipping” or “wrinkling” of DNA during replication.

The removal or addition of even a single nucleotide to a gene

 alters every codon after the mutation, changes reading frame

What is the chromosomal mutation “deletion”?

The loss of one or more gene(s) from the parent chromosome

What is the chromosomal mutation “Duplication”?

The addition of one or more gene(s) that are already present in the chromosome 

What is the chromosomal mutation “Inversion”?

The complete reversal of one or more gene(s) within a chromosome;  the genes are present, but the order is backwards from the parent chromosome

What is the chromosomal mutation “Translocation”?

Chromosomes swap one or more gene(s) with another chromosome