mutations and variation Flashcards
What are the three ways the nucleotide sequence is changed?
substitution, insertion and deletion
What does the insertion or deletion of a nucleotide cause?
frameshift mutation
How can a mutation have no effect?
degenerate nature of genetic code so same amino acid is coded for even though nucleotides have been substituted
What causes an increased likelihood of mutations?
mutagens
How do X-rays increase chance of mutation?
break DNA strands and during repair mutations can occur
How do chemical mutagens cause mutation?
deaminating agents chemically alter bases in DNA
What are the types of mutation?
silent mutations, nonsense mutations and missense mutations
What is a silent mutation?
no change to proteins or activity of any synthesised proteins
What is a nonsense mutation?
a codon becomes a stop codon rather than coding for an amino acid. This results in a shortened protein
What is a missense mutation?
the codon now codes for a different amino acid
What is an example of a beneficial mutation?
the ability to drink milk and process the lactose which helps prevent osteoporosis
What are the types of chromosome mutation that can occur?
Deletion - section of chromosome breaks off and is lost
Duplication - sections of chromosome are duplicated
Translocation - section of one chromosome breaks off and joins another non homologous chromosome
Inversion - section of chromosome breaks off, is reversed and then joins back on
What is a frameshift mutation?
where every successive codon from the point of mutation is changed due to an insertion or deletion of a nucleotide
