Meiosis

Question 1

Process of meiosis

Answer 1

1) before meiosis stars, DNA replicates, so there are two copies of each chromosome called sister chromatids, joined by a centromere
2) Meiosis 1 → spectated homologous pairs
Crossing over creates genetic variation
Independent segregation increase genetic variation
3) Meiosis 2 → separates chromatids
4) Creates 4 haploid cells which at genetically varied

Question 2

How meiosis creates genetic variation

Answer 2

CROSSING OVER
- crossing over between homologous chromosomes
- alleles exchange between chromosomes
- create a new combination of maternal and paternal alelles

INDEPENDENT SEGREGATION
-Random alignment of homologous pairs at equator → random, which chromosome from each pair goes to each daughter cell
- creates different combinations of paternal and maternal chromosomes and alleles in daughter cells
-Random fertilisation, and two gametes fuse to form a zygote

Question 3

Importance of meiosis

Answer 3

• 2 divisions → creates haploid gametes
• diploid number restored at fertilisation
• maintains chromosome number for generations
• independent segregation and crossing over creates genetic variation

Question 4

Chromosome non-disjunction

Answer 4

• Homologous chromosomes fail to separate during meiosis 1 or sister chromatids gait to separate during meiosis 2
  -One gamete has an extra copy of this chromosome
• During fertilisation, zygote has an extra (survive) or one less chromosome (dies)
• arises spontaneously
  -cause genetic diseases

Question 5

Explain the different outcomes of meiosis

Answer 5

• Mitosis produces 2 diploid cells → meiosis produces diploid cells
• Mitosis is 1 division when duster chromatids separate → Meiosis states 2 divisions to separate the sister chromatids
• Mitosis creates genetically identical cells → Meiosis creates genetically varied cells