Question

A bivalent of meiosis I consists of
A. Four chromatids and two centromeres
B. Two chromatids and one centromere
C. Two chromatids and two centromeres
D. Four chromatids and four centromeres

Answer 1

Meiosis is a process of cell division where a single cell divides twice which produces four cells containing half the original amount of genetic information. The cells which facilitate reproduction like sperms in male and eggs in female divide by meiosis cell division.

Complete answer:
During the cell division by the meiosis, one cell divides twice to form four daughter cells and the four daughter cells which originate from the parent cell have half the number of chromosomes of the parent cell. These cells are known as haploid cells. Meiosis division helps in producing the sex cells or gametes which are eggs in female and sperm in males. Meiosis consists of 9 stages which occur between the first time when a cell divides which is known as meiosis I and second time it divides which is termed as meiosis II.
When two replicated homologous chromosomes are associated then it forms the bivalent which is also known as the tetrads and are mainly formed during the pachytene stage of the meiosis. The cells undergo chiasmata formation for the recombination process. Four chromatids and two centromeres are formed during bivalent meiosis I.

Hence, the correct option is A. Four chromatids and two centromeres.

Note: Meiosis I consist of 5 phases during cell division, these 5 phases of meiosis are interphase, prophase I, metaphase I, anaphase I, and telophase I and cytokinesis.