Genetic Diversity Can Arise As A Result Of Mutation Or During Meiosis Flashcards
1
Q
what are gene mutations?
A
- change in the base sequence of chromosomes
- they arise spontaneously during DNA replication (including base deletion and base substitution)
2
Q
what are mutagenic agents?
A
increases the rate of gene mutation
3
Q
why may there not always be a change in the amino acid sequence?
A
- degenerate nature of genetic code = more than one triplet codes for the same amino acid
- mutation may take place in an intron
4
Q
when can mutations in the number of chromosomes arise?
A
they arise spontaneously by chromosomes non-disjunction during meiosis
when the chromosomes fail to separate
5
Q
what happens during meiosis?
A
- two nuclear divisions which result is the formation of 4 haploid cells
6
Q
how does meiosis lead to mutation?
A
- independent segregation of homologous chromosomes
- crossing over between homologous chromosomes
7
Q
explain crossing over.
A
- occurs through prophase 1 of meiosis
- chromatid of each chromosomes wrap around each other forming chiasmata
- when chromosomes separate during anaphase 1, chromatids break at the chiasmata
8
Q
explain independent segregation of homologous chromosomes.
A
- occurs during metaphase 1 of meiosis
- arrangement of maternal or paternal chromosomes is completely random
9
Q
why is meiosis important?
A
- creates genetic variation, so diversity
- halves the chromosome number and at fertilisation the diploid number is restored
