38. The CORRECT sequence of phases during mitosis is:

(A) Prophase, Metaphase, Anaphase, Telophase

(B) Prophase, Anaphase, Metaphase, Telophase

(D) Anaphase, Metaphase, Prophase, Telophase

Correct Sequence of Mitosis Phases

Introduction

Mitosis is the process of nuclear division in eukaryotic cells that ensures the equal distribution of duplicated chromosomes into two genetically identical daughter cells. It plays a crucial role in growth, tissue repair, regeneration, embryonic development, and maintenance of chromosome number across successive generations of somatic cells. Since chromosome segregation must occur with remarkable precision, mitosis follows a highly organized sequence of events controlled by cyclins, cyclin-dependent kinases (CDKs), spindle checkpoint proteins, and various regulatory molecules.

The four principal stages of mitosis are Prophase, Metaphase, Anaphase, and Telophase. Each stage is characterized by specific structural changes in chromosomes, the nuclear envelope, spindle microtubules, and centrosomes.

Correct Answer

Correct Option: (A) Prophase → Metaphase → Anaphase → Telophase

Detailed Explanation

Mitosis proceeds in a fixed chronological sequence beginning with Prophase, followed by Metaphase, Anaphase, and finally Telophase. Each phase prepares the cell for the next, ensuring accurate chromosome segregation.

During Prophase, chromatin condenses into visible chromosomes, the nucleolus disappears, centrosomes migrate toward opposite poles, and the mitotic spindle begins to assemble. In late prophase (prometaphase), the nuclear envelope breaks down, allowing spindle microtubules to interact with chromosome kinetochores.

In Metaphase, chromosomes become maximally condensed and align precisely along the metaphase plate. Each sister chromatid is attached to spindle fibers originating from opposite poles. The spindle assembly checkpoint verifies that every chromosome is correctly attached before chromosome separation begins.

During Anaphase, cohesin proteins holding sister chromatids together are cleaved by separase. Sister chromatids separate and move toward opposite poles through shortening of kinetochore microtubules and elongation of polar microtubules.

Finally, in Telophase, chromosomes reach the spindle poles and begin to decondense. Nuclear envelopes re-form around each chromosome set, nucleoli reappear, and cytokinesis begins or is completed, producing two genetically identical daughter cells.

Explanation of Each Option

Option (A): Prophase → Metaphase → Anaphase → Telophase

This statement is correct. This is the universally accepted sequence of mitotic stages. Chromosomes condense during prophase, align during metaphase, separate during anaphase, and become enclosed within newly formed nuclei during telophase.

Option (B): Prophase → Anaphase → Metaphase → Telophase

This statement is incorrect. Chromosome alignment at the metaphase plate must occur before sister chromatids can separate. Therefore, anaphase cannot precede metaphase.

Option (C): Anaphase → Prophase → Metaphase → Telophase

This statement is incorrect. Anaphase is one of the later stages of mitosis and cannot occur before chromosome condensation and spindle formation in prophase.

Option (D): Anaphase → Metaphase → Prophase → Telophase

This statement is incorrect. The sequence is completely reversed and does not represent the biological progression of mitosis.

Why Option (A) is Correct

The sequence Prophase → Metaphase → Anaphase → Telophase accurately reflects the orderly progression of chromosome condensation, chromosome alignment, sister chromatid separation, and nuclear reformation. Each phase depends upon successful completion of the previous phase, ensuring faithful chromosome inheritance.

Why the Other Options are Incorrect

Why Option (B) is Incorrect

Chromosome separation cannot begin until chromosomes have aligned at the metaphase plate.

Why Option (C) is Incorrect

Anaphase requires spindle formation and chromosome alignment, which occur earlier during prophase and metaphase.

Why Option (D) is Incorrect

The stages are arranged in an incorrect biological order and do not correspond to normal mitosis.

Comparison of All Options

Option	Sequence	Correct or Incorrect	Reason
A	Prophase → Metaphase → Anaphase → Telophase	Correct	Represents the normal order of mitosis.
B	Prophase → Anaphase → Metaphase → Telophase	Incorrect	Anaphase cannot occur before metaphase.
C	Anaphase → Prophase → Metaphase → Telophase	Incorrect	Anaphase is a late mitotic stage.
D	Anaphase → Metaphase → Prophase → Telophase	Incorrect	Completely incorrect sequence.

Events During Each Phase of Mitosis

Mitotic Phase	Major Events
Prophase	Chromosome condensation, spindle formation, disappearance of nucleolus
Metaphase	Chromosomes align at the metaphase plate
Anaphase	Sister chromatids separate and migrate to opposite poles
Telophase	Nuclear envelope re-forms, chromosomes decondense, cytokinesis begins

Summary of Mitotic Changes

Cellular Structure	Prophase	Metaphase	Anaphase	Telophase
Chromosomes	Condense	Align	Separate	Decondense
Nuclear Envelope	Breaks down	Absent	Absent	Re-forms
Mitotic Spindle	Forms	Fully developed	Pulls chromatids apart	Disassembles
Nucleolus	Disappears	Absent	Absent	Reappears

Biological Significance of Mitosis

Mitosis maintains chromosome number and genetic stability in somatic cells by producing two genetically identical daughter cells. It supports growth, embryonic development, tissue regeneration, wound healing, and replacement of aged or damaged cells. Accurate chromosome segregation during mitosis prevents aneuploidy and genomic instability, both of which are associated with developmental abnormalities and cancer.

Final Answer

Correct Option: (A) Prophase → Metaphase → Anaphase → Telophase

The correct sequence of mitotic phases is Prophase, Metaphase, Anaphase, and Telophase. During these stages, chromosomes condense, align at the metaphase plate, separate into daughter chromosomes, and are finally enclosed within newly formed nuclei, ensuring accurate chromosome segregation and formation of two genetically identical daughter cells.