Question

(a) (i) Which cell undergoes meiosis?

(ii)State a reason for your answer in 1(a)(i).

(iii)
Name the phase of cell division in cell Y.

(b) (i)Draw the chromosomal behaviour of cell X and cell Y after each phase in Diagram 1.

(ii)Explain the difference in chromosomal behaviour drawn in 1(b).

(c)Wildan has four siblings from the same parent. But their faces and attitudes are different. Explain how the differences can occur in Wildan's siblings.

Answer 1

(a) (i) Cell X undergoes meiosis.

(ii) This is because cell X has four daughter cells, which are haploid with half the number of chromosomes as the parent cell. Meiosis is a type of cell division that occurs in sexually reproducing organisms to produce haploid gametes that are genetically diverse.

(iii) Cell Y is in metaphase of mitosis.

(b) (i)

Phase Chromosomal behaviour of cell X Chromosomal behaviour of cell Y

Prophase I Homologous chromosomes pair up to form bivalents. Crossing over occurs. Homologous chromosomes pair up to form bivalents. Crossing over occurs.

Metaphase I Bivalents align at the equator of the cell. Bivalents align at the equator of the cell.

Anaphase I Homologous chromosomes separate and move to opposite poles of the cell. Homologous chromosomes separate and move to opposite poles of the cell.

Telophase I Two haploid daughter cells are formed, each with half the number of chromosomes as the parent cell. Two haploid daughter cells are formed, each with half the number of chromosomes as the parent cell.

Prophase II Chromosomes condense and become visible. Chromosomes condense and become visible.

Metaphase II Chromosomes align at the equator of the cell. Chromosomes align at the equator of the cell.

Anaphase II Sister chromatids separate and move to opposite poles of the cell. Sister chromatids separate and move to opposite poles of the cell.

Telophase II Four haploid daughter cells are formed, each with half the number of chromosomes as the parent cell. Four haploid daughter cells are formed, each with half the number of chromosomes as the parent cell.

(ii) The chromosomal behaviour of cell X and cell Y differs in meiosis I, where cell X undergoes the separation of homologous chromosomes, and cell Y undergoes the separation of sister chromatids. In meiosis I, homologous chromosomes pair up to form bivalents, and crossing over occurs, leading to genetic recombination. In anaphase I, homologous chromosomes separate and move to opposite poles of the cell. In contrast, in meiosis II, sister chromatids separate and move to opposite poles of the cell.

(c) The differences in Wildan's siblings can occur due to genetic variation resulting from sexual reproduction. When gametes (sperm and egg cells) are formed during meiosis, genetic recombination occurs, leading to a unique combination of alleles in each gamete. When fertilization occurs, the combination of alleles from both parents creates a unique genotype in the offspring. Additionally, environmental factors and epigenetic modifications can also influence the expression of genes and contribute to differences in physical appearance and behavior among siblings.