4.3 - Mutations and meiosis Flashcards
What is an allele?
alternative version of the same gene
What is a genetic mutation?
A change in the base sequence of chromosomes which results in the formation of a new allele
What is a mutagenic agent?
A factor that increases the rate of gene mutation
Describe the parent and daughter cells produced in meiosis and number of nuclear divisions
diploid parent cell produces 4 haploid daughter cells (gametes) that are genetically different
2 nuclear divisions
How are genetically different daughter cells produced during meiosis?
independent segregation of homologous chromosomes
How can chromosome mutations spontaneously arise during meiosis?
- non-disjunction = failure of homologous chromosomes to separate
- polyploidy = an individual has more than 2 sets of chromosomes
How is genetic variation further increased in meiosis?
- crossing over between homologous chromosomes
- random fertilisation of haploid gametes which produces new allele combinations
Give the six types of mutation
base:
- deletion
- addition
- substitution
- inversion
- duplication
- translocation
How does genetic variation arise in meiosis?
- independent assortment of chromosomes: arrangement of homologous pairs is random
- crossing over of chromatids: exchanging genetic material with other of homologous pair
What is crossing over?
the exchange between of genetic material between two homologous chromosomes resulting in a new combination of alleles
(occurs in meiosis 1)
What is independent assortment?
the alleles of two (or more) different genes get sorted into gametes independently of one another
Describe what happens in meiosis 1 and meiosis 2
1: homologous chromosomes pair up, crossing over at the chiasmata (crossing points) may occur, cell then divides and each daughter cell contains one chromosome from each homologous pair
2: chromatids of each chromosome are separated producing 4 haploid daughter cells
