The diagrams below show chromosomes 21, 22 and 23 in a human cell in different phases of cell division.

here are the answers to Question 2.1:

2.1.1 Identify:

• (a) Structure B: Centromere
• (b) Structure C: Nuclear membrane (or Nuclear envelope)
• (c) The type of gamete that will be formed at the end of this cell division: Sperm cell or Egg cell (or Ovum)

2.1.2 State ONE function of part A during cell division.

• Part A (spindle fibers) is responsible for pulling chromosomes to opposite poles of the cell. (or attaching to centromeres; or forming the spindle apparatus)

2.1.3 Identify the phase in diagram Y.

• Metaphase I

2.1.4 Describe TWO observable differences between the phase identified in QUESTION 2.1.3 and the same phase in mitosis.

• In Metaphase I (meiosis), homologous chromosomes pair up and align at the metaphase plate, forming bivalents. In metaphase (mitosis), individual chromosomes (each with two chromatids) align at the metaphase plate.
• In Metaphase I (meiosis), the centromeres of homologous chromosomes face opposite poles. In metaphase (mitosis), the centromeres of sister chromatids face opposite poles.

2.1.5 Explain the chromosome number in the phase represented in diagram Z.

• Diagram Z represents Prophase I of meiosis.
• In a human cell, the diploid chromosome number is $2n = 46$.
• During Prophase I, the cell is still diploid, meaning it contains 46 chromosomes. Each of these chromosomes has already replicated and consists of two sister chromatids, but the chromosome number is counted by the number of centromeres.