8.1 Origins of genetic variation Flashcards
Suggest factors that increase genetic variation
- mutations
- random assortment and crossing over during meiosis
- random fertilisation during sexual reproduction
what is a mutation
An alteration to the DNA base sequence.
Often arise spontaneously during DNA replication.
Why might a mutation not lead to change in the amino acid sequence?
Because the genetic code is degenerate
meaning the mutation may end up coding for the same amino acid as the original triplet unless a frame shift occurs.
What are addition and deletion mutations?
What is their consequence?
Where one or more nulceotides (bases) are either inserted or deleted from the DNA sequence.
This is more likely to be harmful and significant, as it leads to a frame shift which means the entire amino acid sequence will be different.
What is a substitution mutation?
What is their consequence?
When one nucleotide in the DNA sequence is replaced by another.
This is more likely to be a quiet mutation menaing no change occurs in the amino acid sequence.
How can processes during meiosis create new combinations of alleles?
- random arrangement of chromosomes during lining up
- crossing over of chromatids- to exchange alleles before the first division.
How does random fertilisation bring about genetic variation?
Gametes are haploid cells, meaning they only contain half of a persons DNA
As this is determined by meiosis, every gamete contains different DNA.
Therefore the same two individuals can produce genetically different offspring.
