Chapter 19-Mutations and variation Flashcards
What is a mutation?
A change in DNA base sequence caused by mutagens
What are the different types mutagens?
-Physical mutagens
-Chemical mutagens
-Biological agents
Give an example of a physical mutagen and what they do
Ionisation radiation such as X-rays
Give an example of a chemical mutagen and what they do
Deaminating agent
Give an example of a biological agent and what they do
-alkylating agents:
-base analogs
-viruses
What is a point mutation?
A mutation that only affects ONE nucleotide base
What are the three types of point mutations?
- Substitution
- Insertion
- Deletion
What is a substitution mutation?
A nucleotide base that has been substituted with another nucleotide base
What is a insertion mutation?
When an extra nucleotide is incorporated into the base sequence
What is a deletion mutation?
The removal of a nucleotide from a base sequence
What two types of point mutations result in a FRAME SHIFT MUTATION
Insertion and deletion
Why do insertion and deletionmutations result in a frameshift mutation?
Insertion/ Deletion of a base disrupts the triplet code reading of the codons in the mRNA, leading to the alteration in the amino acid sequence at protein translation
Why does substitution NOT cause frame shift mutation?
The genetic code is DEGENERATE- meaning that multiple codons can code for ONE particular amino acid.
What is a codon?
A sequence of three bases which codes for a particular amino acid
What are the three types of substitution mutations?
-Silent mutation
-Mis-sense mutation
-Nonsense mutation
