GENETIC DIVERSITY Flashcards
What is substitution?
Nucleotide based is replaced with another
What are the three types of gene mutation?
- Substitution
- Insertion
- Deletion
What is insertion?
- An extra nucleotide base is inserted into the sequence causing ‘frameshift’
- All the subsequent bases are shifted down 1 place relative to the twin DNA strand
What is deletion?
- The absence of a nucleotide, causing ‘frameshift’
* All the subsequent bases are shifted back 1 place relative to the twin DNA strand
What are the three categories of mutation effects?
- Neutral
- Harmful
- Beneficial
What are some neutral effects?
• May occur in phenotypically insignificant strand of DNA
• May not result in change of polypeptide primary sequence (because DNA is
degenerate)
• May result in a change of polypeptide primary sequence that does not affect
secondary/tertiary/quaternary structure of protein therefore protein function
unaffected
• May results in a change of polypeptide secondary/tertiary/quaternary structure but
where active site of protein remains the same therefore function still unaffected
What are some harmful mutation effects?
Result in change in final protein shape where protein and active site is deformed and
therefore cannot fulfil function
What are some beneficial mutation effects
• May result in change in final protein shape where the protein performs its function
better than it would have without the mutation
• This is the basis of natural selection and evolution
• The individual is better suited to survival and will pass on the mutation to its
offspring
What is a mutation?
Change in base sequence of chromosomes
When can mutations occur?
During DNA replication
Why do not all base substitutions cause a change?
• Due to the
degenerate nature of the genetic code, not all base substitutions
cause a change in the sequence of encoded amino acids.
What can increase rate of gene mutation?
Mutagenic agents
What can mutations effect?
Mutations can affect 1 nucleotide base, or more than one adjacent base
What is a point mutation?
Where only 1 base is affected
What are the three types of mutation?
- Silent Mutation
- Missense Mutation
- Nonsense Mutation
What is a silent mutation?
No change in amino acid sequence of polypeptide
What is a missense mutation?
○ The mutation changes the code for 1 amino acid
○ 1 amino acid in the sequence is changes
What is a nonsense mutation?
○ The mutation changes the code turning the triplet into a stop codon
○ Instructs the end of polypeptide synthesis
○ The polypeptide is shorter than it would normally be
What is chromosomal non disjunction?
One pair of chromosomes fails to separate, so gamete and zygote have an extra chromosome
How can mutations in the number of chromosomes happen?
Can occur spontaneously through chromosome non dis-junction during meiosis
