Topic 4: Gamete Formation - Meiosis

Question 1

What is meiosis?

Answer 1

reproductive nuclear division

Question 2

What does meiosis produce?

Answer 2

• gametes (ovum and sperm)
• 1 cell (diploid 2n) produces 4 genetically dissimilar gametes (each haploid, n)

Question 3

What are the general steps in meiosis? (4)

Answer 3

1. interphase
2. meiosis I
3. immediately followed by meiosis II
   - between meiosis I and II is interkinesis, NOT INTERPHASE (no DNA replication)

Question 4

What generally occurs in Meiosis I? (2)

Answer 4

• reduction division
• 2n to n

Question 5

What is different about Prophase I in meiosis?

Answer 5

1. homologous xmes attach together to form tetrads (4 chromatids in a row)
2. Crossing over occurs
   - piece of 1 chromatid exchanges with matching piece from a chromatid of the homologous xme

Question 6

Why does crossing over occur?

Answer 6

• acts to increase genetic diversity

Question 7

What is different in metaphase I in meiosis?

Answer 7

• 23 TETRADS line up along the equator

Question 8

What is different in Anaphase I of meiosis? (2)

Answer 8

• tetrads (homologous xm pairs) separate and migrate to opposite poles
  ie. one homologous chromosome (with 2 sister chromatids) goes to each pole
• chromatids DONT separate

Question 9

What is different in telophase I of meiosis? (3)

Answer 9

• after meiosis I and cytokinesis
• each new cell has 23 different chromosomes (half the xme number so haploid)
• these cells do not have homologous xmes

Question 10

What is Meiosis II? (2)

Answer 10

• same as mitosis except with 23 xmes instead of 46
• turns diploid germ cells into haploid gametes

Question 11

See diagrams in notes for germ cell

Answer 11

thanks