20.1 gene mutation Flashcards
when do gene mutations arise?
dna replication
what is mutation?
change in quantity / structure of dna
what are the 6 types of mutation?
1- substitution
2- translocation
3- inversion
4- deletion
5- addition
6- duplication
what are the 2 ways that dna mutations are caused? explain.
1- spontaneous
- arise during dna replication without outside influence
2- mutagens
- higher mutation rates from exposure eg. high energy ionising radiation, NO2, tobacco smoke
what is substitution of bases?
1 nucleotide is substituted by another nucleotide with a different base
what are the 3 outcomes of substitution? explain.
1- formation of stop codon
- stops translation & significantly different final protein
2- different codon codes for another amino acid
- forms protein with different shapes & functionality which affects binding & active site
3- different codon codes for same amino acid
- no effect due to degenerate code
what is resulted from deletion of bases? explain how it affects the protein formed.
causes frameshift to the left as dna nucleotide is lost
- nucleotides are read in the wrong sets of 3 -> different amino acid sequence forms different polypeptide -> non-functional protein
what mutations causes a frameshift to the right? explain how.
addition
- extra nucleotide is added
duplication
- 1/more nucleotides are repeated
what occurs during translocation of nucleotides?
base pairs are relocated from 1 area to another, usually between 2 homologous chromosomes
what is resulted from a translocated polypeptide?
fusion protein - 2 unrelated gene sequences are transcribed together
what is inversion of nucleotides?
group of nucleotides get reinserted in the same position but in inverse order
what are the advantages for mutations?
produce genetic diversity for natural selection and speciation
what are the disadvantages of mutations?
- almost always harmful - disrupts normal cell activity
- derives are less suited to environment & less likely to survive
