Meiosis

Question 1

Why does meiosis occur?

Answer 1

• It is used to make gametes in sexual reproduction

Question 2

What do gametes needs to be?

Answer 2

• They need to contain one member of each homologus pair
• be genetically different from one another to increase variation in population
• achieved by crossing over and independent assortment

Question 3

How are haploid cells produced in Meiosis?

Answer 3

• Prior to division each pair of homologous pair is replicated
• each replicated chromosome is made up of two identical sister chromatids
• the first division separates the homologous pairs
• the second
  pair separates sister chromatids
• Meioisis 1 is called the reduction division - the cells no longer have from diploid to haploid pairs

Question 4

Diploid Vs Haploid

Question 5

When does crossing over take place? and what is it?

Answer 5

• prophase 1
• chromsomes are joined by bivalent sections of one chromosomes are swapped which the corresponding bits of the other chromosome

Question 6

What is independent assortment?

Answer 6

• each homologous pairs aligns itself on the metaphase plate independently of the alignments of other pairs

Question 7

When does independent assortment happen?

Answer 7

• Meiosis one - homologous pairs are randomly assorted
• meiosis 2 - sister chromatids are randomly assorted

Question 8

what is prophase 1 in meiosis?

Answer 8

chromatids condense, homologous chromosomes form bivalents,crossing over occurs

Question 9

what is metaphase 1 in meiosis?

Answer 9

bivalents line up at the equator, independent assortment occurs

Question 10

what is anaphase 1 in meiosis?

Answer 10

• spindle fibres pull homologous chromosomes opposite poles of the cell

Question 11

what is telophase 1 in meiosis?

Answer 11

• followed by cytokinesis
• nuclear envelope forms around nuclei

Question 12

what is prophase 2 in meiosis?

Answer 12

chromosomes condense, spindle fibres re-form nuclear envelope breaks down again

Question 13

what is metaphase 2 in meiosis?

Answer 13

• chromosomes randomly arrange themselves on spindle fibres at equator by centromeres, so independent assortment occurs

Question 14

what is anaphase 2 in meiosis?

Answer 14

chromatids are pulled by apart by contracting spindle fibres to poles of the cell

Question 15

what is telophase 2 in meiosis?

Answer 15

followed by cytokinesis
nuclear envelope forms around new haploid nuclei