Question

31. what major events occur during anaphase?

a. chromosomes artach to spindle fibers

b. chromosomes replicate.

c. chromosomes are located at opposite ends ot the cell and nuclear envelopes begin to re- form

d. sister chromatids separate and are pulled to opposite poles

e. chromosomes condense and the nuclear envelope diappears.

32. which of the following statements abouts GPCR signaling is not true?

a. the same GPCR can have multiple effects via different downstream signaling pathways.

b. the Galphq subunit when activated will hydrolyze GTP into GDP.

c. the bindinf of a signaling molecules fo a GPCR can lead to activation of many heterimeric G protein complex.

d. the second messengers generated through the GPCR signaling pathways can directly activate some ion channels.

Answer 1

Ans.

Let us first examine each answer options:

(a) Chromosomes artach to spindle fibers - It occurs in the Metaphase, the 3rd Step of Mitosis. In this step the spindle is formed fully and the centrosomes are located at the opposite poles. Chromosomes are aligned on the equator and each sister sister chromatids (chromosomes) is attached to the spindle fibers that originates from the opposite poles.

(b) Chromosomes replicate - It occurs in the S Phase or the Interphase of Cell cyle before mitosis or meiosis.The replication of DNA is done so that there is enough DNA available for splitting into daughter cells during the further cell cylce process.

(c) Chromosomes are located at opposite ends ot the cell and nuclear envelopes begin to re-form -It occurs in the Telophase, the 5th Step of Mitosis. Chromosome at the opposite poles starts to condense and a nuclear envelope material began to surround each of the chromosome pairs.Break down of mitotic spindle takes place.

(d) Sister chromatids separate and are pulled to opposite poles -It occurs in the Anaphase,the 4th step of mitosis. The break down of cohesin protein results into the separation of sister chromatids,which now becomes individual chromosomes and are pulled towards the opposite poles.The length of the non-kinetochore spindle fiber increases,thus elongating the cell.

(e)Chromosomes condense and the nuclear envelope diappears - It occurs in the Prophase,the 1st stage of mitosis. Condensation of chromosomes happen and spindle fibers starts emerging from the centrosomes.Nuclear envelope starts breaking down and began to disappear.

Hence, the answer is Option (D) sister chromatids separate and are pulled to opposite poles, which is the major event occuring during the anaphase step of mitosis.