Question

How many chromosomes are shown in the illustration in Figure 12.8? Are they duplicated? How many chromatids are shown?

Short answer

The number of chromosomes shown in the figure is six. The chromosomes in the figure are duplicated (meaning there are two copies of DNA).

The number of chromatids in the figure is 12; chromatid is a single strand of the chromosome.

Step-by-step solution

Chromosomes

The chromosome is a thread-like structure that is formed of proteins and DNA. It is the genetic material that passes from parents to offspring. Condensation of this genetic material occurs at the prophase of meiosis and mitosis. The two sister chromatids are joined by the kinetochore (it is the proteinaceous structure that is present at the specific location of the DNA).

Metaphase

Metaphase is one of the steps of mitosis and meiosis. In this event, the chromosomes align at the equatorial plate. Metaphase occurs after the prophase process.

The chromosomes are attached with spindle fibers. Metaphase is the crucial stage for the alignment of the chromosomes so that in the next stage (anaphase), these chromosomes get separated.

Duplication and segregation of chromosomes

The chromosomes get duplicated in the synthesis phase of the cell cycle, while the segregation occurs at the phase. The chromosomal content becomes double the original amount in the S phase, and these get segregated in anaphase I and anaphase -II.

Thus, in the figure, six chromosomes are in the duplicated form, creating 12chromatids.