Gene mutation 9.1 Flashcards
What is a gene mutation?
A change in the quantity or base sequence of DNA in an organism
Which mutations are inheritable?
Mutations that occur in the formation of gametes
What are the types of gene mutations that occur in DNA replication?
Substitution and deletion
What happens in a substitution mutation?
One base in a DNA triplet is replaced with another, which changes 1 triplet code in a polypeptide
How does a substitution mutation effect the overall protein produced?
If the amino acid replaced is involved in forming bonds then the tertiary structure will change
If the protein is an enzyme the active site may no longer fit a specific substrate
Why might some substitution mutations not change the polypeptide produced?
DNA is degenerative. The altered triplet may code for the same amino acid as the original one
What happens in a deletion mutation?
1 nucleotide base is lost/deleted from the DNA sequence, causing a left frame shift and changing all further triplet codes
What happens in an insertion mutation?
1 nucleotide base is added to the DNA sequence, causing a right frame shift and changing all further triplets
What are the 2 types chromosome mutation
- changes in whole sets of chromosomes
2. non-disjunction (change in the number of individual chromosomes)
Give an example of a mutation due to a change in a whole set of chromosomes
Polyploidy
where plants have 3 or more sets of chromosomes rather than the usual 2
What is non-disjunction
A chromosome mutation that occurs when individual homologous pairs fail to separate during meiosis, resulting in a gamete having one more or one fewer chromosome.
Give an example of a disease caused by non-disjunction chromosome mutation
Down’s syndrome (extra chromosome 21)
