Meiosis

Question 1

What is ‘n’

Answer 1

The number of types of chromosomes and organism has

Question 2

Describe diploid cells

Answer 2

• contain 2n chromosomes
• pairs of each type (homologous chromosomes)
• the product of fertilisation

Question 3

Describe haploid cells

Answer 3

• Contain n chromosomes
• one of each type
• are gamete’s or sex cells

Question 4

Basic human life cycle

Answer 4

• diploid parents produce haploid gametes through meiosis
• two haploid gametes fuse together to form a diploid zygote
• zygote grows by mitosis

Question 5

Describe meiosis 1

Answer 5

• homologous chromosomes pair up in synapsis
• crossing over rearranges alleles on homologous chromosomes
• independent segregation of homologous to produce 2 haploid cells

Question 6

Describe meiosis 2

Answer 6

• cells align single chromosomes in metaphase 2
• chromatids are separated
• produce 4 haploid cells that are genetically non-identical

Question 7

Describe independent segregation in meiosis

Answer 7

• 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

Question 8

Describe crossing over in meiosis

Answer 8

• 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