match the following

Component	Description
A. endosteal niche	1. versatile cells that both generate bone and control the differentiation of HSCs
B. osteoblasts	2. line the blood vessels and also regulate HSC differentiation
C. reticular cells	3. send processes connecting cells to bone and blood vessels, and unexpectedly
D. sympathetic neurons	4. can control the release of hematopoietic cells from the bone marrow.

#Question id: 2975

#Unit 2. Cellular Organization

Following statements are regarding to the Surveillance mechanisms in cell cycle regulation.

A. Surveillance mechanisms known as checkpoint pathways establish dependencies among cell cycle events and ensure that the next cell cycle event does not occur prior to the completion of a preceding event.

B. In response to DNA damage, two related protein kinases, ATM and ATR, are recruited to the site of the damage, where they activate signaling pathways that lead to cell cycle arrest, repair, and under some circumstances, apoptosis.

C. The spindle assembly checkpoint pathway, which causes initiation of anaphase, utilizes Mad2 and other proteins to regulate APC/CCdc20, which targets securing and mitotic cyclins for ubiquitinylation.

D. The spindle position checkpoint pathway prevents mitotic CDK inactivation when the spindle is mispositioned. In this pathway, localized activators and inhibitors and a sensor that shuttles between them allow cells to sense spindle position.

Which of the following statement is incorrect?

#Question id: 2599

#Unit 2. Cellular Organization

The mRNA from the trp operon has a half-life of only about____

#Question id: 2601

#Unit 2. Cellular Organization

Condition of basal level transcription (BLT);

#Question id: 2604

#Unit 2. Cellular Organization

Best inducer of the lac operon;

#Question id: 2605

#Unit 2. Cellular Organization

The precursor of trp is;

#Question id: 2607

#Unit 2. Cellular Organization

The precursor amino acid + enzyme of trp is ;