Following statements are regarding to the early development in sea urchin.

A. most cells of the 16-cell embryo, the large micromeres are autonomously specified.

B. large micromeres inherit maternal determinants that were deposited at the vegetal pole of the egg; these become incorporated into the large micromeres at the fourth cleavage.

C. The conditionally specified large micromeres are now able to produce paracrine and juxtacrine factors that autonomously specify the fates of their neighbors.

D. Large micromeres become skeletogenic mesenchyme cells that will leave the blastula epithelium, enter the blastocoel, migrate to particular positions along the blastocoel wall, and then differentiate into the larval skeleton.

Which of the following statement is false?

#Question id: 4299

#Unit 3. Fundamental Processes

Lactate dehydrogenase (LDH) can exist as various tetrameric isozymes. Extracts from different rat tissues were run on a nondenaturing polyacrylamide gel and stained for LDH activity, as shown below. Standard tetramers of M subunits (M4) and H subunits (H4) were run alongside the tissue extracts. Which of the following is the subunit composition of the isozyme running at position 2 ?

#Question id: 4300

#Unit 3. Fundamental Processes

Find correct order of cotranslational translocation in endoplasmic reticulum

A. Transfer of the nascent polypeptide–ribosome to the translocon leads to opening of this

translocation channel to admit the growing polypeptide adjacent to the signal sequence, which is transferred to a hydrophobic binding site next to the central pore. Both the SRP and SRP receptor, once dissociated from the translocon, hydrolyze their bound GTP and then are ready to initiate the insertion of another polypeptide chain.

B. As the polypeptide chain elongates, it passes through the translocon channel into the ER lumen, where the signal sequence is cleaved by signal peptidase and is rapidly degraded.

C. The SRP and the nascent polypeptide chain–ribosome complex bind to the SRP receptor in

the ER membrane. This interaction is strengthened by the binding of GTP to both the SRP and its receptor.

D. The ER signal sequence emerges from the ribosome; it is bound by a signal recognition particle (SRP).

#Question id: 4301

#Unit 3. Fundamental Processes

Which of the following proteins prevents eukaryotic mRNAs from being recruited to the ribosome prior to egg fertilization

#Question id: 4351

#Unit 3. Fundamental Processes

A Cycle of Peptide-Bond Formation Consumes

#Question id: 20400

#Unit 3. Fundamental Processes

#Question id: 20401

#Unit 3. Fundamental Processes