Difference Between Cleavage And Mitosis

Both cleavage and mitosis are cell division processes. Cleavage is a type of cell division that happens during early embryonic development in animals, whereas mitosis is a general process of cell division that occurs in both animals and plants for growth and repair.

Table of Contents:

Cleavage and Its Types
Mitosis and Its Phases
Cleavage Vs Mitosis
Practice Problems On Cleavage And Mitosis
Frequently Asked Questions

Cleavage and Its Types

Cleavage refers to the division of cells during the early stages of embryonic development. It occurs in animal cells and rapidly divides the fertilised egg (zygote) into multiple smaller cells called blastomeres. Successive rounds of cell division characterise cleavage without significant growth or differentiation of the cells. Cleavage aims to increase the cell number and create a multicellular embryo.

Types of Cleavages

The two main types of cleavage patterns in animal embryonic development are as follows:

Holoblastic Cleavage

There is a whole division of the fertilised egg (zygote) and subsequent blastomeres into smaller cells. Eggs with small to moderate levels of yolk will experience this kind of cleavage. Two types of holoblastic cleavage are:

Radial Cleavage: Radial cleavage occurs parallel or perpendicular to the polar axis, resulting in blastomeres aligning in a radial pattern.
Bilateral Cleavage: Bilateral cleavage is a pattern of cell division that divides the embryo into right and left halves, resulting in cells similar in size and shape.
Rotation Cleavage: Rotation cleavage involves rotational movements of the blastomeres, leading to the rotation of daughter cells relative to each other.
Spiral Cleavage: Spiral cleavage occurs in animals such as annelids and molluscs, resulting in blastomeres arranged in a spiral pattern.

Meroblastic Cleavage

Meroblastic cleavage occurs in eggs with a large amount of yolk, restricting cell division to only a small portion of the egg. The yolk is a nutrient reserve for the developing embryo, but it inhibits complete cell division, forming a blastoderm or disc-shaped structure. Two types of meroblastic cleavage are:

Discoidal Cleavage: Cell divisions occur in a small disc-shaped area at the animal pole of the egg, forming a layered structure on top of the yolk, providing nourishment to the embryo.
Superficial Cleavage: Cell divisions occur in the peripheral cytoplasm of the egg, resulting in a syncytial or multinucleated embryo.

Determinate and Indeterminate Cleavage

Various factors, including genetics and environment, regulate cell fate and developmental potential during early embryogenesis. During early embryogenesis, the terms determinate and indeterminate cleavage refer to the developmental capabilities of cells.

Determined cleavage is a type of cell division where each cell's destiny is predetermined during the early stages of embryonic development. This kind of cleavage is typical in lower animals and some invertebrates, where each blastomere has a fixed fate.
Indeterminate cleavage is a cell division pattern in which the developmental fate of each cell is not defined early in embryonic development. It is usually found in creatures with a strong regeneration ability, such as invertebrates and vertebrates, including humans. It allows for the production of identical twins and the restoration of lost or injured body parts.

Mitosis and Its Phases

Cell division in somatic cells results in the formation of two genetically identical daughter cells, a process known as mitosis.

Phases of Mitosis

Mitosis has a number of distinct phases that guarantee the precise separation of chromosomes and genetic material into daughter cells. This process is essential to preserve the genetic stability and integrity of the organism.

Interphase: Before mitosis begins, the cell undergoes a phase called interphase. During this phase, the cell grows, DNA is replicated, and the cell prepares for division. Interphase is made up of three subphases: G1 (gap 1), S (synthesis), and G2 (gap 2).
Prophase: During cell division, chromatin condenses into visible chromosomes, the nuclear envelope breaks down, and a mitotic spindle is formed. The centrosomes move to opposite poles, and spindle fibres attach to the kinetochores of the chromosomes.
Metaphase: During metaphase, the chromosomes condense and line up at the cell's equatorial plane (also known as the metaphase plate). Meanwhile, the spindle fibres attach to the chromosome’s centromeres.
Anaphase: During cell division, paired sister chromatids separate and move towards opposite ends of the cell, aided by the shortening of spindle fibres. This process is known as telophase.
Telophase: After the chromosomes have reached the poles, they decondense into chromatin and are enveloped by nuclear membranes. Finally, the spindle fibres disassemble.
Cytokinesis: During the final phase of cell division, the cytoplasm divides to create two daughter cells. In animal cells, a cleavage furrow forms to constrict the cell membrane, while in plant cells, a cell plate develops and eventually becomes a new cell wall.

Following cytokinesis, the two daughter cells enter interphase, carrying out their biological duties and continuing to grow.

Cleavage Vs Mitosis

Cleavage	Mitosis
Occurs in early embryonic development	Occurs in somatic cells
Process of cell division during embryo development	Process of cell division for growth, repair, and asexual reproduction
Rapid cell divisions without significant growth or differentiation	Cell divisions with growth and differentiation
Divisions result in smaller cells called blastomeres	Divisions result in two genetically identical daughter cells
Determines the increase in cell number during early embryogenesis	Maintains the cell number and tissue integrity in an organism
It can be either holoblastic (complete) or meroblastic (incomplete)	Follows a specific sequence of phases: Interphase, Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis
Occurs in animals, particularly during the blastula stage	Occurs in both animals and plants
Establishes the basic body plan and developmental axes	Ensures genetic stability and proper distribution of chromosomes
Does not involve the formation of a spindle apparatus	Requires the formation of a spindle apparatus for chromosome segregation
This leads to the formation of a multicellular embryo	Results in the formation of two daughter cells ready for further growth and cellular functions

Practice Problems On Cleavage And Mitosis

Q1. Identify the process that involves rapid cell divisions without significant growth or differentiation?

A. Cleavage
B. Meiosis
C. Mitosis
D. Fertilisation

Ans: A. Cleavage

The rapid cell division known as cleavage occurs in the absence of substantial differentiation or growth. The number of cells in the growing embryo is increased by this process, which takes place throughout the early stages of embryonic development.

Q2. Which of the following best sums up the role of mitosis?

A. Rapid cell divisions during early embryonic development
B. Determination of cell fate during organogenesis
C. Formation of two genetically identical daughter cells
D. Production of gametes for sexual reproduction

Ans: C. Formation of two genetically identical daughter cells

The cell division procedure known as mitosis produces two genetically identical daughter cells. It is essential for an organism's development, repair, and asexual reproduction.

Q3. When do the sister chromatids part and move towards the opposite poles of the cell during mitosis?

A. Prophase
B. Anaphase
C. Metaphase
D. Telophase

Ans: B. Anaphase

Anaphase is a mitotic phase in which sister chromatids split and travel to opposing poles of the cell. The spindle fibre shortening facilitates this separation, resulting in the appropriate distribution of genetic material into the daughter cells.

Frequently Asked Questions

Q1. Does cleavage occur in mitosis?
Answer : Cleavage and mitosis are two separate processes. Cleavage occurs during early embryonic development, while mitosis is a cell division process that occurs in somatic cells.

Q2. Is cleavage division mitotic or meiosis?
Answer : Cell division during cleavage is mitotic, meaning that cells divide without reducing the chromosome number. This process occurs during development.

Q3. What stage of mitosis does cleavage form?
Answer : Cleavage occurs during cytokinesis, which is the final stage of mitosis. This is when the cytoplasm divides to form two separate cells.