Section 4:Genetic diversity Flashcards
What are the two types of mutation?
Gene mutation:A change in the sequence in bases in DNA
Chromosome mutation:A change in the number or sturcture of chromosomes
What are mutagenic agents and give four examples
Mutagenic agent is something which can increase the rate of mutation, this can be chemical or physical
Example:UV light, nitrous acid, gamma rays and viruses
What are the different types of gene mutation?
- Substitution of base
- Deletion of base
- Addition of a base
Why might the amino acid produced not change
What happens when a substitution mutation occurs?
Substitution mutations result in a change of one base, this could change the result of the amino acid
The amino acid may not change as the genetic code is degenerate
What disease is a result of a base substitution mutation?
Sickle cell disease (anaemia)
The substitution of one base causes an amino acid change =resulting in a slightly different version of the protein chain in haemoglobin being produced~leads to a sickle shaped haemoglobin produced
Is the amino acid produced always changed
What happens when a deletion mutation occurs?
A deletion of a base results in a frameshift which changes a series of amino acids
Deleting a base can lead to codons no longer being read properly as bases are read as triplets ,therefore the subsiquent bases will be shifted foward by one base
What disease is a result of a base deletion mutation?
Cystic Fibrosis
Deletion of one triplet coding for the the 508th amino acid in the gene causes a faulty protein to be produced
This leads to thick mucus that clogs around the lungs
Three points
Describe how a base deletion affects the amino acid sequence
- Frameshift mutation~due to the non-overlapping nature of the genetic code
- Nucleotide base is removed every reading frame from the point of the mutation is shifted
- This means that every amino acid downstream will be shifted
Give an example
What is meant by non-disjunction?
Homolgous pairs don’t seperate during meiosis
An example of this is downs syndrome~an extra chromosome 21
What is caused by a base insertion?
The reading frame is shifted which changes the sequnce of amino acids produced
What are gametes?
Reproductive sex cells that fuses with another gamete during fertilisation
What is an allele?
One number of alternative forms of a gene
What are homologous chromosomes?
One maternal chromosome and one paternal chromosome
Why is meiosis needed?
It is necessary to halve the number of chromosomes going into the cell
