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Define variation
Differences within or between species
Define interspecific
Mutation between species
Define intraspecific
Mutation within a species
What are the 3 main causes of variation
Mutations, meiosis, random fertilisation
Define mutation
Any change to the nucleotide sequence in DNA
Where do mutations occur
In introns
Why do mutations occur
Due to the degenerative nature of the genetic code
Define silent mutations
Mutations which do not effect the amino acid sequence
What nature do mutations occur
Randomly and spontaneously
Define mutagens
Things that increase rate of mutation
Give some examples of mutagens
Ionising radiation, environmental chemicals and HPV/viruses
Name the point mutations
Addition, deletion and substitution
Describe a deletion mutation
Removal of one base sequence
Describe a substitution mutation
Switching on base sequence for another
What does meiosis form
4 non-genetically identical daughter cells
What is the name of the meiosis product
Haploid gametes
What two ways can meiosis produce variation
Independent assortment/segregation, crossing over
Describe independent assortment/segregation
Chromosomes line uptown the equator of cells in homologous pairs - but could be in a different order
Define homologous pairs
Chromosomes with the same gene in the same loci but could have different alleles
Describe variation by crossing over
Homologous pairs of chromosomes form a bivalent at the chiasmata, equal amounts of DNA are swapped between chromosomes
Describe the chiasmata
the cross over point of two chromosomes
Define non-disjunction
A chromosome mutation which results in gametes having too many or too few chromosomes
Why do most mutations not effect the polypeptide
Because the code is degenerate
