The control of gene expression Flashcards
Define mutation.
A permanent, random change in the nucleotide sequence of DNA.
Mutations can be caused by errors during what process?
DNA replication.
What are mutagens?
Agents that are capable of increasing the rate of genetic mutation.
What is a substitution mutation?
Where one or more bases are swapped with another.
What is a deletion mutation?
Where one or more bases are removed from the sequence, causing a frame shift.
What is an addition mutation?
Where one or more bases are added to the sequence, causing a frame shift.
What is a duplication mutation?
Where one or more bases are repeated, causing a frame shift.
What is an inversion mutation?
Where a sequence of bases is reversed, not causing a frame shift.
What is a translocation mutation?
Where a sequence of bases is moved from one location in the genome to another. This could be movement within the same chromosome or movement to a different chromosome.
The order of DNA bases in a gene determines…
…the sequence of amino acids in a particular polypeptide. If a mutation occurs in a gene, the sequence of amino acids in the polypeptide that it codes for could be changed.
What effect would a mutation have on the functionality of an enzyme if that mutation affects its final 3D shape?
If the shape of the active site of the enzyme is altered, there’s the possibility that the substrate may no longer be complementary in shape to the active site and so an enzyme-substrate complex won’t be able to form. If the substrate can no longer bind to the enzyme, the enzyme won’t be able to catalyse the reaction.
What are hereditary mutations?
A gamete containing a mutation for a genetic disorder or a type of cancer is fertilised, so the mutation is present in the new foetus.
Beneficial hereditary mutations allow for…
…Evolution.
Why can the genetic code be described as degenerate?
There are more possible base triplet combinations (64) than there are amino acids (20), therefore some amino acids are coded for by more than 1 base triplet.
What the degeneracy of the genetic code mean for mutations and their effect?
Not all mutations will always result in a change in the amino acid sequence of the polypeptide. A substitution could give a codon that codes for the same amino acid.
What is a silent mutation?
Where a mutation has no effect on the amino acid sequence and therefore doesn’t change the polypeptide.
Which types of mutation almost always change the sequence of amino acids of a polypeptide?
Addition, deletion and duplication mutations. These mutations change the number of bases in the sequence.
What is the term for the base triplets that follow on from the point of mutation?
Downstream.
Name some mutagenic agents.
Ultraviolet radiation X-ray radiation Gamma radiation Alpha radiation Beta radiation
How can mutagens act as a base?
Chemicals called base analogs can substitute for a base during DNA replication, changing the base sequence in the new DNA.
An example is 5-bromouracil. This is a base analog that can substitute for thymine and pair with guanine (instead of adenine), causing a substitution mutations in the new DNA.
How can mutagens act as a base?
Some chemicals can delete or alter bases.
For example, alkylating agents can add an alkyl group to guanine, which changes the structure so that it pairs with thymine instead of cytosine.
How can mutagens change the structure of DNA?
Some types of radiation can change the structure of DNA, which causes problems during DNA replication.
For example, UV radiation can cause adjacent thymine bases to pair up together.
