Topic 8.1 Origins of genetic variation Flashcards
Suggest factors that increase genetic variation
- Mutations
- Random assostment and crossing over suring meiosis
- Random fertilisation during sexual reproduction
What is a mutation?
An alteration to the DNA base sequence. Often arises spontaneously during DNA replication.
Why might a mutation not lead to a 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 origional triplet unless a frame shift occurs.
What are addition and deletion mutations?
Where one or more nucleotides (bases) are either inserted or removed 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?
When a nucleotide in the DNA sequence is replaced by another. This is more likely to be a quiet mutation, meaning no change occurs in the amino acid sequence.
How can processes during mitosis create new combinations of alleles?
- Random arrangement of chromosomes during lining up
- Crossing over of chromatids 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 indiviuals can produce genetically different offspring.
