Genetic diversity can arise as a result of mutation or during meiosis Flashcards
What is a mutation?
Any change in the base sequence or quantity of DNA
What can a change in the base sequence of a gene change?
The sequence of amino acids
Why might the amino acid sequence not always be changed after a mutation?
Because the genetic code is degenerate
What are the two types of mutation?
Substitution, deletion
What is substitution?
When one nucleotide in the DNA sequence is replaced by another
Why might a substitution not always be harmful?
As the substituted nucleotide may code in that triplet for the same amino acid
What is deletion?
When a nucleotide in the DNA sequence is lost
What can the loss of a single nucleotide lead to?
A frame shift
What are the two forms of mutations in chromosomes?
Polyploidy, non-disjunction
What is polyploidy?
When changes occur in the chromosomes so an individual has three or more sets of chromosomes instead of two
What is non-disjunction?
When chromosomes fail to separate correctly in meiosis. As a result the gametes and zygotes formed will have one more or one less chromosome than they should.
What is meiosis?
A form of cell division where four genetically different daughter cells are produced
What is the main role of meiosis?
The production of haploid gametes
What are the two ways genetic variation is achieved in meiosis?
Independent assortment of chromosomes and crossing over of chromatids
What happens during independent assortment of chromosomes?
During meiosis 1 homologous chromosomes line up in pairs, the arrangement of these cells is random, meaning that the division into the daughter cells is also random
What happens during the crossing over of the chromatids?
When pairs of chromosomes line up they can exchange some of their genetic material. Crossing over occurs when one chromosome may swap places with the same part of its homologous pair leading to a different combination of alleles on the gene.
What happens in the first stage of meosis?
Homologous chromosomes pair up whereby crossing over at the chiasmata may take place. The cell then divides whereby each daughter cell contains one chromosome from each homologous pair
What happens in the second stage of meiosis?
The chromatids of each chromosome are separated producing 4 haploid daughter cells
