Mutations Flashcards
(25 cards)
What is a gene mutation?
A change in the base sequence of DNA. This can arise spontaneously during DNA replication.
When are mutations more likely to occur?
During DNA replication - during interphase of the cell cycle - S phase.
When do mutations occur?
Spontaneously.
What is a mutagenic agent?
A factor that increases the rate of genetic mutation.
What can mutations cause?
A different amino acid sequence in the polypeptide.
What happens if the amino acid sequence changes?
When the protein is modified into its tertiary structure, it’ll form hydrogen bonds, ionic bonds and disulfide bridges in different places and will fold differently. This results in a different 3D shape and thus a non-functioning protein.
What is something serious that mutations can cause?
Cancer
What are the two types of mutagenic agents?
High energy and ionising radiation
Carcinogens
What are 5 examples of high energy and ionising radiation?
Beta particles
Alpha particles
X-rays
Gamma Rays
Ultraviolet light
Why is ultraviolet light still considered radiation if it is not ionising?
It is still high enough to cause damage and disrupt the structure of DNA.
What are 3 examples of carcinogens?
Peroxides
Mustard Gas
Tobacco Smoke
What are carcinogens?
Chemicals that can alter the structure of DNA and interfere with transcription.
What are the 6 types of gene mutations?
Addition
Deletion
Substitution
Inversion
Duplication
Translocation
What is an addition mutation?
One extra DNA nucleotide being added to the sequence.
Describe the effect of an addition mutation.
All subsequent codons are altered. This is known as a frame shift. All the altered codons can code for different amino acids and result in a very different sequence of amino acids and thus resulting in a non functioning protein.
What is a deletion mutation?
The deletion of a nucleotide in a sequence.
Describe the impact of a deletion mutation.
One nucleotide is removed from the DNA sequence. Causes a frame shift to the left. Changes sequence of amino acids in primary structure of polypeptide. Changes position of the H bonds, ionic bonds and disulfide bridges in tertiary structure of protein. Changes tertiary structure.
What is a substitution mutation?
One nucleotide has been substituted for a different nucleotide.
Explain the possible effects of a substitution mutation.
DNA base is replaced by a different base. This changes one triplet so changes one mRNA codon. So one amino acid in polypeptide changes - tertiary structure may change if position of the bonds change. OR amino acid doesn’t change due to the degenerate nature of the genetic code.
What is inversion mutation?
A section of nucleotides detach and rejoins inverted.
Describe the impact of an inversion mutation.
Different amino acids are coded for in this region.
What is a translocation mutation?
A section of bases on one chromosome detaches and attaches to a different chromosome.
Describe the impact of translocation mutation.
Can cause significant impacts on gene expression and thus resulting in a different phenotype.
What is a duplication mutation?
A section of DNA bases are duplicated within the DNA sequence.
