Chapter 9, Problem 22A

Summary Introduction

Introduction:

Cells reproduce by a cycle of growing and dividing called the cell cycle. There are three main stages of a cell cycle; interphase, mitosis and cytokinesis. Prophase is the first stage of mitosis in which a dividing cell spends most of the time. The nuclear membrane disintegrates and nucleolus disappears. The chromatin tightens and condenses into chromosomes. Chromosomes are shaped like an X. Each half of this X chromosome that was replicated in interphase is called sister chromatid. The sister chromatids are attached at the center with a structure called centromere.

Answer to Problem 22A

Correct answer :

The correct answer is option A. spindle formation

Explanation of Solution

Explanation/justification for the correct answer:

Option A. spindle formation−During prophase, microtubules form in the cytoplasm. These microtubule structures are called spindle fibers. Spindle fibers help in moving and organizing the chromosomes before cell division. The spindle formation will be hampered if vinblastine drug is used as it interferes with the microtubule synthesis.

Hence this is the correct option.

Explanation for incorrect answer:

Option B. DNA replication −DNA replication process is not interfered by the intake of vinblastine drug. Vinblastine interferes with synthesis of microtubules which are important for spindle fiber formation. It has nothing to do with DNA replication. Hence, this is not the correct option.

Option C. carbohydrate synthesis- Vinblastine drug interferes with synthesis of microtubules which are important for spindle fiber formation. It has nothing to do with carbohydrate synthesis. Hence this is not the correct option.

Option D. disappearance of the nuclear envelope−During prophase the nuclear membrane disintegrates and nucleolus disappears.Vinblastine drug interferes with synthesis of microtubules which are important for spindle fiber formation. It does not interfere with the disappearance of the nuclear envelope. Hence this is not the correct option.