Cellular Control Flashcards
What is a mutation?
A change in the base sequence of DNA
What are the 3 main types of mutation?
- Substitution
- Deletion
- Insertion
Of one or more nucleotides within a gene
What is a substitution mutation?
Where one (or more) bases is swapped for another
What is it called if only 1 nucleotide is affected?
A point mutation
What are the 3 types of point mutation?
- Silent
- Missense
- Nonsense
What are silent mutations?
When the altered base sequence still codes for the same amino acid
What are missense mutations?
When the substituted base does code for a different amino acid in the primary protein structure and as a result, the final protein cannot function properly
What are nonsense mutations?
When the base sequence is altered in such a way that the triplet code changes from an amino acid code to a “stop” codon. This will result in a shorter protein which won’t function properly
What is a deletion mutation?
Where one (or more) nucleotides are removed from the DNA sequence
What is an insertion mutation?
Where one (or more) nucleotides are added to the DNA sequence
What are the consequences of mutations?
- Primary protein structure is altered
- Will twist and fold differently, altering secondary and tertiary structures
- 3D shape and function altered
What is a point mutation?
When only 1 nucleotide is affected in the sequence
What types of mutation would you expect to have the greatest consequences?
Both insertion and deletion would alter the whole triplet code from the point of mutation onwards
= Frameshift
What makes a mutation neutral?
- If it occurs in the introns
- If it results in a silent mutation
- If the altered triplet code results in a different a.a in the sequence but it’s so chemically similar to the original that it makes no difference to final protein
- If it codes for a completely different a.a bit this a.a isn’t crucial for how the final protein works
- If it results in a different final protein but this doesn’t affect the survival chances of the organism
DON’T INCREASE/DECREASE CHANCES OF SURVIVAL
What makes a mutation beneficial?
- If it has advantageous effects on organisms and increases chances of survival
Give an example of a beneficial mutation
Humans in some parts of the world can digest lactose due to a mutation
What makes a mutation harmful?
- If it has a disadvantageous effect on an organism and reduces the chance of survival
Give an example of a harmful mutation
Cystic fibrosis
Give an example of how a mutation can be both beneficial and harmful
Eye colour
- Blue eyes beneficial in temperature regions of the world, but not in regions where there is high light intensity
- Have less pigmentation in iris so more light can get through to retina = better vision
- Brown eyes better in high light intensity or can cause cateracts
What is a frame shift mutation?
A mutation caused by the insertion or deletion of a base pair/pairs in DNA, resulting in the shift of nucleotides.
This alters the reading frame of the sequence and changes every successive codon from the point of mutation
What leads to a frame shift mutation?
Insertion and deletion
What are the 3 effects different mutations can have?
- Neutral
- Beneficial
- Harmful
What is a mutagen?
A chemical, physical, or biological agent that causes mutations
Give an example of a physical mutagen
Ionising radiations, such as x-rays
What do ionising radiations do?
Break one or both DNA strands
Give an example of a chemical mutagen
Deaminating agents
What do deaminating agents do?
Chemically alter bases in DNA
Give an example of a biological agent
Viruses