9.1 gene mutation Flashcards
mutation
change to quantity or base sequence of dna of an organism
inherited mutation
occurs during formation of gametes
produces distinct differences between individuals
gene mutation
change to one or more nucleotide bases or change in sequence of bases in DNA
2 types of gene mutation
base substitution
base deletion
base substitution
nucleotide in DNA molecule is replaced by another nucleotide with different base
bad consequence of base substitution
DNA triplet codes for different amino acid(replaces original)
polypeptide produced differs in single amino acid
may not form same bonds that determine tertiary structure of final protein
protein is different shape and can’t function properly(e.g. active site no longer fits substrate)
no consequence of base substitution
DNA triplet still codes for same amino acid
- degenerate code
no change in polypeptide produced so mutation has no effect
base deletion
nucleotide is lost from normal DNA sequence
consequence of base deletion
sequence of bases in DNA is read in triplets
1 deleted nucleotide causes all triplets in sequence to be read differently as has shifted to left by one base
codes for completely different sequence of amino acids
polypeptide is unlikely to function correctly
chromosome mutation
changes in structure or number of whole chromosomes
2 types of chromosome mutation
1- changes in whole sets of chromosomes
2- changes in number of individual chromosomes
changes in whole sets of chromosomes
organisms have 3 or more sets of chromosomes rather than 2
polyploidy
occurs mostly in plants
changes in number of individual chromosomes
when individual homologous pairs of chromosomes fail to separate during meiosis(non-disjunction)
gamete has one more or one fewer chromosome
fertilisation occurs and offspring has more or fewer chromosomes than normal in all body cells
