What is the Difference Between Aster and Spindle Fibres

The key difference between aster and spindle fibres is that aster fibres are formed around the centrioles and project out towards the pole, while spindle fibres arise from the pole towards the centre.

Aster fibres and spindle fibres are essential for cell divisions: mitosis and meiosis. Both are components of spindle apparatus. Spindle apparatus is made of spindle fibres, motor proteins, and chromosomes. In animal cells, they are made of microtubule arrays. Aster fibres and spindle fibres are microtubules.

CONTENTS

1. Overview and Key Difference
2. What are Aster Fibres
3. What are Spindle Fibres
4. Similarities – Aster and Spindle Fibres
5. Aster vs Spindle Fibres in Tabular Form
6. Summary – Aster vs Spindle Fibres

What are Aster Fibres?

Aster fibres are star-shaped cellular structures that consist of a centrosome and are associated with microtubules during early mitotic and meiotic stages in animal cells. Aster fibres are made up of microtubules and are a part of the cytoskeleton. Aster fibres do not form in plant cells. Microtubules make up the Aster rays, and they radiate from the centrosome. The fibres provide support to the chromosomes to guide them to end up in the right place during cell division. They help the chromosomes to line up and arrange in the centre of the nucleus. Aster fibres pull half of the genetic information to each side of the nucleus during the process; therefore, the nucleus divides in half, leaving two daughter nuclei.

Aster fibres initially appear during prophase in cell division. The two centrosomes with asters migrate to the opposite sides of the nucleus to form mitotic spindles. Thus, the aster fibres organize the spindle fibres, which extend from both poles and the fibres that attach to chromosomes at the kinetochores. The nuclear envelope separates into fragments, and mitotic spindles form during pro-metaphase. The spindle fibres move chromosomes to the centre during metaphase. The orientation of aster fibres determines the plane of division of cells during cell division.

What are Spindle Fibres?

Spindle fibres are microtubules that form the mitotic and meiotic spindle during cell division. They are protein structures, and they divide the genetic materials in a cell. Spindle fibres are also known as mitotic spindles during mitosis since they produce genetically identical daughter cells and meiotic spindle during meiosis since it produces gametes with half the number of chromosomes than the parent cell. Therefore, spindle fibres have to equally divide chromosomes into two daughter cells from a parent cell during cell division.

During this process, spindle fibres move chromosomes by attaching to chromosomal arms and centromeres. In prophase, spindle fibres form at the opposite poles of the cell, and when the cell elongates, the spindle fibres stretch. Sister chromatids attach to spindle fibres at their kinetochores. During metaphase, spindle fibres are called polar fibres, and they extend from cell poles toward the midpoint. Chromosomes are arranged in the middle by the force of spindle fibres. During anaphase, spindle fibres shorten, and sister chromatids are pulled toward the opposite poles. During telophase, spindle fibres disperse as the chromosomes separate.

What are the Similarities Between Aster and Spindle Fibres?

• Aster and spindle fibres are two types of fibres involved in mitosis and meiosis.
• They are formed from microtubules.
• Both fibres are present in animal cells.
• Moreover, both are components of spindle apparatus.

What is the Difference Between Aster and Spindle Fibres?

Aster fibres are a variant of microtubules that arise from centrioles. Spindle fibres arise from the poles towards the centre. Thus, this is the key difference between aster and spindle fibres. Moreover, aster fibres are not attached to the chromosome, while microtubules separate the chromosomes to the poles with the help of spindle fibres. So, this is also a difference between the aster and spindle fibres. Besides, aster fibres are only seen in animal cells, while spindle fibres are seen in both plant and animal cells.

The below infographic presents the differences between aster and spindle fibres in tabular form for side by side comparison.

Summary – Aster vs Spindle Fibres

Aster fibres and spindle fibres are essential for cell division. They are components of spindle apparatus. Both fibres are made up of microtubules. Aster fibres are formed near centrioles and radiate towards the pole, while spindle fibres arise from the poles towards the centre. Hence, this is the key difference between aster and spindle fibres. Aster fibres are star-shaped cellular structures that consist of a centrosome and are associated with microtubules during early mitotic and meiotic stages. Spindle fibres are microtubules that form the mitotic and meiotic spindle during cell division.

Reference:

1. Bailey, Regina. “What Are Asters?” ThoughtCo.
2. “Spindle fibers.” Nature News, Nature Publishing Group.

Image Courtesy:

1. “Spindle apparatus” By Lordjuppiter – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Spindle chromosomes-en” By Spindle_chromosomes.png: Silvia3derivative work: Dawn08 (talk) – Spindle_chromosomes.png (CC BY-SA 3.0) via Commons Wikimedia