A1- Meiosis

Question 1

Process of meiosis

Answer 1

-before meiosis starts. DNA replicates so there’s 2 copies of each chromosome (sister chromatids joined by centromere)
-homologous pairs line up randomly and one from each pair move either side of the cell
-independent segregation (increases genetic variation in gametes)
-crossing over - recombination occurs where chromosomes swap genetic material
-homologous chromosomes separate
-4 new daughter cells are formed

Question 2

How does meiosis create genetic variation

Answer 2

1)crossing over between homologous chromosomes
- alleles exchanged between chromosomes
-creates new combination of maternal and paternal alleles on chromosome
2) independent segregation of homologous chromosomes
- random alignment of homologous pairs at equator > random which chromosomes from each pair goes to each daughter cell
-creates different combinations of maternal and paternal chromosomes and alleles in daughter cells
3) random fertilisation when 2 gametes fuse to form zygote

Question 3

Importance of meiosis

Answer 3

-2 divisions > creates haploid gametes (half number of chromosomes)
-diploid number restored at fertilisation
-maintains chromosome number from one generation to the next
-independent segregation and crossing over creates genetic variation

Question 4

Why is meiosis important?

Answer 4

-so that gametes formed are haploid
-therefore fuse to make a cell with a diploid number of chromosomes.
-Without meiosis the number of chromosomes would increase with each generation
-therefore it is needed to keep the number constant/stable