Question

72. Looking into your microscope, vou spot an unusual coll Instead of the typical rounded cell shape, the cen dcell shape, the cell has a very narrow middle separating two bulging ends. It sort of looks like the number or to this cell is two buiging ends. It sort of looks like the number 81 You realize that A) undergoing cytokinesis. C) in the G1 phase of interphase. B) in the S phase of interphase. D) about to undergo mitosis. 73. The phase of mitosis during which the mitotic spindle begins to form is A) interphase. B) prophase. C) metaphase. D) anaphase. 74. During which phase of mitosis do the chromosomes line up on a plane equidistant from the two spindle poles? A) prophase B) metaphase C) anaphase D) telophase 75. At the start of mitotic anaphase A) the centromeres of each chromosome come apart. B) the chromatid DNA replicates. C) nuclear envelopes begin to form around the chromosomes. D) equivalent and complete collections of chromosomes have reached the two poles. 76. During which phase of mitosis does the nuclear envelope re-form? A) anaphase B) metaphase C) prophase D) telophase 77. Which of the following is a feature of plant cell division that distinguishes it from animal cell division? A) formation of a cell plate B) formation of a cleavage furrow C) lack of cytokinesis D) production of four (rather than two) new cells per mitotic division 78. Which of the following features likely accounts for the difference between plant and animal cell cytokinesis? A) Animal cells lack the microfilaments required for forming a cleavage furrow. B) Animal cells lack chloroplasts. C) Plant cells have cell walls. D) Plant cells have two sets of chromosomes, animal cells have one set of chromosomes. 79. Which of the following must occur for a plant or animal to grow and develop normally? A) The organism must receive a supply of the appropriate hormones from its parents B) The organism must be able to control the timing and rate of cell division in different parts of its body. C) Sufficient light must be available to stimulate cell division. D) Sufficient oxygen must be available to stimulate cell division. 80. When animal cells are grown in a petri dish, they typically stop dividing once they have formed a single, unbroken layer on the bottom of the dish. This arrest of division is an example of A) mitosis Sphase. B) density-dependent inhibition. C) lack of nutrients.

Answer 1

72. A

Cytokinesis is the process by which cytoplasm of a cell divides so as to give rise to two daughter cells. It occurs after the mitotic division has been completed.

Second statement is incorrect because no such bulges and narrow middle of the cell is observed in S phase of mitosis. In this phase the DNA duplicates.

Third statement is incorrect because in gap 1 phase of cell division, the cell prepares itself to divide. It undertakes duplication of its organelles, proteins and cytoplasm. The shape of the cell is normal, no bulges are seen.

Fourth statement is incorrect because when bulges are seen in a Cell, it means the cell has completed mitosis, not initiated Mitosis.

73. B

Spindle fibres begin to form in first stage of mitosis, process. Prophase is characterized by the disintegration of nuclear membrane and condensation of chromatin into chromosomes. Spindle fibres are assembled by centrioles in animal cell and spindle Apparatus in plant cell. They elomgate and shorten in response to chromosome movement during cell division.

74. B

The lining of chromosomes during meiosis is a characteristic feature of metaphase. All the chromosomes come to lie in the middle of the cell called as equatorial plate or metaphasic plate. It is an imaginary Axis. The chromosomes are held in the equator by spindle fibres which attach the centromere of the chromosomes to the centrioles located at the opposite poles of the cell.

Anaphase is characterized by separation of sister chromatids from each other and their movement toward the opposite poles of the cell.

Telophase is the last stage of mitosis characterized by the reappearance of nuclear membrane and decondensation of chromosomes into chromatin.

75. A

Anaphase is explained above.

Second statement is incorrect because DNA is replicated during S phase of Mitosis.

Third statement is incorrect because nuclear membrane reappears in telophase and disintegrates in prophase.

Fourth statement describes the feature of late anaphase

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