Genetic variation Flashcards
Genetic mutation
A genetic mutation is a change to one or more nucleotide bases in the base sequence of DNA which results in the formation of a new allele
They can arise spontaneously during DNA replication
Three types of genetic mutation
Substitution, Deletion and insertion
Substitution
One base is replaced
Deletion
One base is lost resulting in a frameshift
Insertion
A base is added resulting in a frameshift
Three results of genetic mutation
Silent , nonsense and missense
Silent
No change in amino acid sequence due to degenerate code
Nonsense
Results in formation of a stop protein level codon
Missense
Results in a formation of a different amino acid
Why might a genetic mutation cause an enzyme to stop working
1) A missense mutation is a result of a new amino acid
2) This amino acid changes the primary structure which changes the tertiary structure as bonds are in different places
3) This changes the shape of the enzymes active site
4)Enzymes active site and substrate are no longer complementary and cant form an enzyme-substrate complex
Polyploid
A result of Non-disjunction which is when changes can occur in whole new sets of chromosomes so that an individual has three of more sets of chromosomes instead of two
Non-disjunction
When chromosomes fail to separate in meiosis I or chromatids fail to separate in meiosis I so gametes will could have one more or one less chromosome then they should ( Causes genetic variation )
Mutagenic agent
Increases the rate of mutation
E.G UV radiation, Smoking, Carcinogen, X-ray
One way in which genetic variation can occur apart from meiosis and mutations
The random fusion of gametes creates random allele combinations
