3.4.3 Genetic diversity can arise as a result of mutation or during meiosis Flashcards
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
Genetic code is degenerate so mutation may end up coding for same amino acid as the original triplet
Mutation may occur in intron
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
What is a deletion mutation
When a nucleotide in the DNA sequence is lost
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 mutagenic agent
Factors that increase rate of gene mutation
What is polyploidy chromosome mutation
Where an individual has three or more sets of chromosomes instead of two
What is chromosome non-disjunction
When chromosomes fail to separate correctly in meiosis, resulting in gametes with one more or less chromosome than normal
What is meiosis
A form of cell division that produces four genetically different haploid cells known as gametes
How does meiosis differ from mitosis
Meiosis produces 4 genetically diff cells with half the number of chromosomes as parent cells
Mitosis produces 2 genetically identical cells with same number of cells as parent
What happens during meiosis 1
- Homologous chromosomes pair to form bivalents
- Crossing over
- Cell divides into two. Homologous chromosomes separate randomly. Each cell contains either maternal or paternal copy
What happens during meiosis II
- Independent segregation of sister chromatids
- Each cell divides again, producing 4 haploid cells
In which two ways does meiosis produce genetic variation
- Crossing over
- Independent assortment of homologous chromosomes and sister chromatids
