Which, if any, of the following statements is incorrect?

I. In X-chromosome inactivation, the inactivated X chromosome is epigenetically silenced by a transcript, the XIST RNA, that is produced from the active X chromosome.

II. The XIST RNA works by coating most of the X chromosome that is to be inactivated and then recruiting Polycomb proteins to condense the chromosome.

III. The inactivated X chromosome carries the kinds of histone modification that are typical of heterochromatin.

IV. The pattern of X-chromosome inactivation is made randomly but once it has been established the same pattern of X-inactivation is propagated through all mitotic and meiotic cell divisions.

#Question id: 2985

#Unit 2. Cellular Organization

Use the figure to answer the question below. The unlettered circle at the top of the figure shows a diploid nucleus with four chromosomes that have not yet replicated. There are two pairs of homologous chromosomes, one long and the other short. One haploid set is black, and the other is gray. The circles labeled A to E show various combinations of these chromosomes. What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis? 

#Question id: 2986

#Unit 2. Cellular Organization

During ubiquitin-mediated protein degradation in various events of cell cycle, ubiquitin-protein ligases ubiquitinylate substrate proteins, marking them for degradation by proteasomes. Cyclins are degraded through the action of two different ubiquitin-protein ligases, SCF and the anaphase-promoting complex or cyclosome. Following statements are regarding to SCF and APC/C.

A. SCF controls the G1–S phase transition by degrading G1/S phase cyclins and, CDK inhibitory proteins.

B. APC/C degrades S phase and mitotic cyclins, thereby promoting the exit from mitosis.

C. SCF and APC/C are multi-subunit ubiquitin-protein ligases that belong to the RING finger family of ubiquitin protein ligases.

D. SCF and APC/C belong to the different ubiquitin-protein ligase family, their regulation is same.

E. SCF recognizes its substrates only when they are phosphorylated.

F. SCF and APC/C both recognizes its substrates only when they are phosphorylated.

Which of the following is incorrect?

#Question id: 2987

#Unit 2. Cellular Organization

Following statements are regarding the goals of gap phases.

(i) to prepare for the next phase of the cell cycle.

(ii) to check that the previous phase of the cell cycle has been completed appropriately.

(iii) to inhibits CDKs activity.

(iv) to enhance servillance mechanisms.

Which of the following is correct?

#Question id: 2988

#Unit 2. Cellular Organization

Use the figure to answer the question below. 

If the cell whose nuclear material is shown in the figure continues toward completion of mitosis, which of the following events would occur next?

#Question id: 2989

#Unit 2. Cellular Organization

Use the figure to answer the question below.

In the figure, G1 is represented by which numbered part(s) of the cycle?

#Question id: 2990

#Unit 2. Cellular Organization

Mitotic CDK complexes are maintained in an inactive state through inhibitory phosphorylation of the CDK subunit. Two highly conserved tyrosine and threonine residues in mammalian CDKs are subject to regulated phosphorylation.

The following table enlists genes and phenotypes observed on mutation of these genes but not correctly matched. Which one of the following combinations is correctly matched ?