Question

Centromere is required for:
A. Movement of chromosomes towards poles
B. Cytoplasmic cleavage
C. Crossing over
D. Transcription

Answer 1

Hint: Eukaryotic chromosome has a specialized region known as the centromere. The centromere is the position of a complex of several proteins. These proteins are called as the kinetochores, During the process of mitosis, several spindle microtubules are connected to each kinetochore.

Complete answer:
The centromere is the portion of the chromosomes where the two sister chromatids are connected together. It is very important for transfer chromosomes towards poles. During mitosis, the spindle fibers are connected to the centromere through the kinetochore. Their physical function is to serve as the assembly site for kinetochores which are a highly complex multi protein structure and are responsible for the actual events of chromosome separation. The event of chromosome separation involves the binding of microtubules and signaling to the cell cycle machine when all chromosomes have been adopted for correct attachments to the spindle and it is secure for cell division to continue to completion and for the cell cycle machine.

Cleavage is the process of division of cytoplasm in the cells in the early developing embryo. In this process, with each successive separation, there is approximately reduction of the cytoplasm into half the amount that is present in each daughter cell than before the division, and therefore the ratio of nuclear to cytoplasmic content increases. The cytoplasmic cleavage doesn’t require centromere.

The process of crossing or recombination is the exchange of chromosome segments between non-sister chromatids during the meiosis cell division. Crossing over produces new gene combinations in gametes that are not present in either parent, which contribute to genetic diversity. This process does not involve centromeres.

Eukaryotes enable transcription factors to first bind to the promoter region in order to carry out the process of transcription and then help to recruit the necessary polymerase. RNA Polymerase II is the polymerase responsible for the transcription of mRNA.

Hence, The correct answer is option (A).

Note: The centromere is present in every cell and is an important component of the cell division. It is a particular sequence of DNA in a chromosome. It is especially useful in the process of cell division. During mitosis, the spindle fibers are connected to the centromeres through kinetochores and all chromosomes are arranged in an equator plane. After this, the chromosomes pass towards their respective poles and the division of the cells takes place.