Meiosis Flashcards
1
Q
What is ‘n’
A
The number of types of chromosomes and organism has
2
Q
Describe diploid cells
A
- contain 2n chromosomes
- pairs of each type (homologous chromosomes)
- the product of fertilisation
3
Q
Describe haploid cells
A
- Contain n chromosomes
- one of each type
- are gamete’s or sex cells
4
Q
Basic human life cycle
A
- diploid parents produce haploid gametes through meiosis
- two haploid gametes fuse together to form a diploid zygote
- zygote grows by mitosis
5
Q
Describe meiosis 1
A
- homologous chromosomes pair up in synapsis
- crossing over rearranges alleles on homologous chromosomes
- independent segregation of homologous to produce 2 haploid cells
6
Q
Describe meiosis 2
A
- cells align single chromosomes in metaphase 2
- chromatids are separated
- produce 4 haploid cells that are genetically non-identical
7
Q
Describe independent segregation in meiosis
A
- during metaphase 1, pairs of homologous chromosomes align on the metaphase plate
- orientation of on pair is random in respect to another
- due to different paternal/maternal alleles, this can produce genetically non-identical gametes when meiosis is repeated
8
Q
Describe crossing over in meiosis
A
- synapsis occurs when homologous chromosomes ‘pair up’ in meiosis 1
- non-sister chromatids overlap forming chiasmata
- same section of homologous DNA are exchanged by recombination
- due to different alleles, new allele sequences are created
