You are interested in a new type of autosomal dominant mutation that gives purple eyes in Drosophila. You have a true-breeding purple-eyed line carrying a mutation that you call pr-1. You have isolated a second purple-eyed mutation that you call pr-2, which you have established in a true-breeding line that also carries a recessive marker st, which gives stubby legs. You cross a fly from the pr-1 line to a fly from the st, pr-2 line producing F1 females which you then cross to males from a true breeding st line (normal eyes). From this cross, 1000 progeny flies can be categorized into four different phenotypic classes:

                             

Normally, 3-factor crosses give eight different phenotypic classes, why does this particular cross give only four?

#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 ?

#Question id: 2991

#Unit 2. Cellular Organization

Early observations of a cultured cell line indicated that the cells did not exhibit either density-dependent inhibition or anchorage dependence. What do these observations suggest about this cell line?