Question

Please explain

Anaphase, Metaphase, Prophase, Telephase and Interphase and what are their orders. Thank you.

Answer 1

Answer:

Order of cell cycles = Interphase----prophase----metaphase----anaphase ----telophase

Explanation:

Cell cycle:

Cell cycle is an orderly series of changes that occurs in a cell by which it duplicates its contents and divides into two. Cell cycle consists of two phases – Inter phase and M – phase. Both of them have a number of sub – stages.

Inter phase:

When a cell divides, it is necessary that its chromosomes and genes also duplicate themselves. The duplication of genes occur during interphase, which is a period of interval between two successive cell divisions, when the cell prepares itself for the division.

During this stage nucleus and cytoplasm are very active metabolically, synthesizing and storing all these substances which are essential for cell division.

During interphase the following processes takes place

1. Replication of DNA and histone proteins
2. Synthesis of energy rich compounds and proteins
3. Duplication of centriole in animal cells.

The interphase lasts more than 95% of the duration of cell cycle. The interphase is divided into three sub stages namely phase, S – phase and phase.

G1 phase:

It comes immediately after the cell division and is characterised by the general growth of cell. The various substances (proteins and nucleotides) necessary for the synthesis of DNA are formed in this phase.

S – phase:

S – phase is called synthesis phase. This phase is marked by the duplication of DNA and histone proteins. As a result of this the amount of DNA is doubled.

G2 – phase:

It is the second growth phase, also called post – synthetic phase or pre mitotic phase. Cell size increases. The nucleolus increases in size due to a accumulation of ribosomal RNA and proteins. Mitochondria and plastids undergo division. Microtubules and other substances directly involved in mitosis are produced. Multiplication of other cell organelles also occur. The chromosomes appear as diffused long coiled and indistinct chromatin fibres.

1. Prophase: It is the first phase of karyokinesis and is of long duration, in which chromatin fibres condense to form chromosomes. Further condensation makes chromosomes shorter and thicker. Then each chromosome splits longitudinally consisting of two identical halves or chromatids. They are held together by centromere. The nucleolus disappears. Two centrioles continue their migration towards the poles. Finally nuclear membrane breaks down and disperses into cytoplasm as elements of endoplasmic reticulum.

​2. Metaphase: During this phase formation of spindle and orientation of chromosomes takes place. The cytoplasm around each centriole arranges as radiating fibres. This structure is called aster. Soon the cytoplasm between the asters differentiates into spindle fibres or microtubules. The middle part of the spindle is called equatorial plate or equator. The chromosomes arrange themselves in a regular manner at the equator in such a fashion that their centromeres lie on the equator and arms are oriented towards the poles. This is called as orientation. The chromosomes are attached to the spindle fibres at their contromeres. Each chromosomes becomes more compact and short and its two chromatids separate except at the centromere which has not yet divided.

3. Anaphase: It is the shortest of all the stages in the mitotic cycle. During anaphase two things happens, the centromere divides and chromatids move to the opposite poles. The centromere of each chromosome divides so that each chromatid contain a separate centromere and behaves as a chromosome. Chromatids begin to move towards the opposite poles and spindle fibres also move towards their respective poles. During their movement towards the poles the chromosomes look like U, V or J shape. Since the centromere is also divided each pole gets the same number of chromatids as present in the parent.

4. Telophase: This is the last phase in which two daughter cells are formed. Events occurred in prophase will be reversed in telophase. Chromosomes reach the opposite poles. Nuclear membrane develops around the chromosomes. Nucleolus reappears. Spindle fibres and asters begin to disappear. The chromosomes become long thread like structures which lose their identity. Each daughter nucleus gets the same number of chromosomes as present in the parent cell.