Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 2: Problem 7

How do spindle fibers form and how do chromosomes separate in animal cells?

Short Answer

Expert verified
Answer: Spindle fibers form during the prometaphase stage of mitosis by extending from centrosomes located at opposite poles of the cell. Composed of microtubules, the spindle fibers attach to the chromosomes at protein structures called kinetochores. During the anaphase stage, spindle fibers shorten, pulling apart sister chromatids and moving them to opposite poles of the cell, ensuring equal distribution of genetic material between the two daughter cells.

Step by step solution

01

1. Overview of Mitosis

Mitosis is a cellular process that ensures the equal distribution of genetic material between two daughter cells. It consists of five stages: prophase, prometaphase, metaphase, anaphase and telophase.
02

2. Formation of Spindle Fibers (Prometaphase)

During prometaphase, spindle fibers begin to form. The nuclear envelope breaks down, allowing spindle fibers to extend from centrosomes (microtubule organizing centers) located at opposite poles of the cell. The spindle fibers are made of microtubules, which are long protein structures that can grow and shrink. As the microtubules extend, they eventually overlap to form a bipolar structure called the mitotic spindle.
03

3. Chromosome Condensation

In prophase, the genetic material in the cell (DNA) becomes densely packed, resulting in the formation of structures called chromosomes. Each chromosome is composed of two sister chromatids, which are identical copies of DNA connected at a point called the centromere.
04

4. Attachment of Spindle Fibers to Chromosomes

During prometaphase, spindle fibers form connections with the chromosomes. Specifically, some spindle fibers attach to protein structures called kinetochores, which are located at the centromeres of the chromosomes. These interactions are critical for the proper alignment and separation of chromosomes.
05

5. Alignment of Chromosomes (Metaphase)

During metaphase, the chromosomes, connected to the spindle fibers, become aligned at the center of the cell, known as the metaphase plate. The attachment of spindle fibers to the kinetochores ensures equal tension on each sister chromatid, preventing premature separation.
06

6. Separation of Chromosomes (Anaphase)

In anaphase, the sister chromatids are pulled apart as the spindle fibers shorten, moving the separated chromatids to opposite poles of the cell. The process is driven by the depolymerization of microtubules. Once the sister chromatids reach the cell poles, they are considered individual chromosomes.
07

7. Completion of Mitosis (Telophase and Cytokinesis)

During telophase, a nuclear envelope re-forms around the separated chromosomes at each pole, creating two separate nuclei. In animal cells, the process of cytokinesis (cell division) occurs through the formation of a cleavage furrow, leading to the physical separation of the two daughter cells, each with an identical set of chromosomes.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

What is the significance of checkpoints in the cell cycle?

Kuliev and Verlinsky (2004) state that there was a relatively high number of separation errors at meiosis I. In these cases the centromere underwent a premature division, occurring at meiosis I rather than meiosis II. Regarding chromosome 21 what would you expect to be the chromosome 21 complement in the secondary oocyte in which you saw a single chromatid (monad) for chromosome 21 in the first polar body? If this secondary oocyte was involved in fertilization, what would be the expected consequences?

During meiosis I, assuming no crossing over, what chromatid combination(s) will be present at the completion of prophase? Draw all possible alignments of chromatids as migration begins during early anaphase.

A species of cereal rye (Secale cereale) has a chromosome number of \(14,\) while a species of Canadian wild rye (Elymus canadensis) has a chromosome number of \(28 .\) Sterile hybrids can be produced by crossing Secale with Elymus. (a) What would be the expected chromosome number in the somatic cells of the hybrids? (b) Given that none of the chromosomes pair at meiosis I in the sterile hybrid (Hang and Franckowlak, 1984 ), speculate on the anaphase I separation patterns of these chromosomes.

Compare chromosomal separation in plant and animal cells.
See all solutions

Recommended explanations on Biology Textbooks

Organ Systems

Read Explanation

Ecological Levels

Read Explanation

Genetic Information

Read Explanation

Microbiology

Read Explanation

Reproduction

Read Explanation

Control of Gene Expression

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free