DNA Mutations and Repair Flashcards
What is MUTATION?
Permanent change to the nucleotide sequence in DNA
How do mutations arise?
- Mistakes made during DNA REPLICATION
- DNA damage from environmental agents
- Spontaneous hydrolytic reactions
What happens during deamination?
Cytosine is changed to Uracil
How does UV radiation cause mutations in DNA?
By forming THYMINE DIMERS where carbons 5 and 6 in each amino acid become linked
How do intercalating agents cause mutations?
By inserting between two adjacent base pairs in a molecule.
Leads to incorporation of additional base on opposite strand.
Give an example of a spontaneous hydrolytic reaction and how it causes mutations
Depurination.
Results in the deletion of a base.
does NOT break the phosphodiester bond
What are the types of mutation?
- Point mutations - single base pair change
- Insertions - extra base pairs inserted into DNA
- Deletions - base pair deleted from DNA
What are the THREE types of point mutations?
- Missense
- Nonsense
- Silent
What is a MISSENSE mutation?
A change in an encoded amino acid causing a change in the DNA sequence
What is a NONSENSE mutation?
A change in a coding region that creates a stop codon
What is a SILENT mutation?
A change in a coding region that does not affect the encoded amino acid
How do INSERTIONS and DELETIONS cause mutations?
By altering the codon and changing the reading frame, resulting in a FRAMESHIFT MUTATION
What is the NUCLEOTIDE EXCISION REPAIR pathway?
DNA repair pathway
What disease is caused by a missing nucleotide excision repair pathway?
Xeroderma pigmentosum
What kind of mutation is sickle cell anemia?
Point mutation
