6) Discuss different phases of the cell cycle with a suitable diagram.

-

6.) Discuss different phases of the cell cycle with a suitable diagram.

answer :

A.)

Cell Cycle

The cell is the basic structural and functional unit of any living being. It is the fundamental building block, which when combined with similar cells forms a tissue and organs. A cell comprises several organelles:

  1. Cytoplasm
  2. Cytoskeleton
  3. Endoplasmic reticulum (ER)
  4. Golgi apparatus
  5. Lysosomes and peroxisomes
  6. Mitochondria
  7. Nucleus
  8. Plasma membrane
  9. Ribosomes

The cell undergoes a series of events that result in the duplication of cell along with the DNA. This is known as the cell cycle. Let us have a look at the events taking place in the division of cell during a cell cycle.

Also Read: Difference between Karyokinesis and Cytokinesis

Cell Cycle Definition

“Cell cycle refers to the series of events that take place in a cell, resulting in the duplication of DNA and division of cytoplasm and organelles to produce two daughter cells.”

cell cycle

What is Cell Cycle?

The cell cycle was discovered by Prevost and Dumas (1824) while studying the cleavage of zygote of Frog. It is a series of stages a cell passes through, to divide and produce new cells.

This entire process where with the help of one single parent cell a new cell population grows and develops is known as the cell cycle. 

Also Read: Meiosis I

Phases of Cell Cycle

Cell cycle or cell division refers to the series of events that take place in a cell leading to its maturity and subsequent division. These events include duplication of its genome and synthesis of the cell organelles followed by division of the cytoplasm.

Human cells exhibit typical eukaryotic cell cycle and take around 24 hours to complete one cycle of growth and division. The duration of the cycle, however, varies from organism to organism and cell to cell.

A typical eukaryotic cell cycle is divided into two main phases:-

Interphase

Also known as the resting phase of the cell cycle; interphase is the time during which the cell prepares for division by undergoing both cell growth and DNA replication. It occupies around 95% time of the overall cycle. The interphase is divided into three phases:-

  • G1 phase (Gap 1) – G1 phase is the phase of the cell between mitosis and initiation of replication of the genetic material of the cell. During this phase, the cell is metabolically active and continues to grow without replicating its DNA.
  • S phase (Synthesis) – DNA replication takes place during this phase. If the initial quantity of DNA in the cell is denoted as 2N, then after replication it becomes 4N. However the number of chromosomes does not vary, viz., if the number of chromosomes during G1 phase was 2n, it will remain 2n at the end of S phase. The centriole also divides into two centriole pairs in the cells which contain centriole.
  • G2­ phase (Gap 2) –During this phase, the RNA, proteins, other macromolecules required for multiplication of cell organelles, spindle formation, and cell growth are produced as the cell prepares to go into the mitotic phase.

Some cells like cardiac cells in the adult animals do not exhibit division and some others only divide to replace those cells which have been either damaged or lost due to cell death. Such cells which do not divide further attain an inactive G0 phase also known as quiescent phase after they exit the G1 phase. These cells remain metabolically active but do not divide unless called upon to do so.

M phase

This is the mitotic phase or the phase of the equational division as the cell undergoes a complete reorganization to give birth to a progeny that has the same number of chromosomes as the parent cell. The other organelles are also divided equally by the process of cytokinesis which is preceded by mitotic nuclear division. The mitotic phase is divided into four overlapping stages:-

  1. Prophase,
  2. Metaphase,
  3. Anaphase, and
  4. Telophase

Mitosis

mitosis

The process by which a eukaryotic cell separates the nuclear DNA and chromosomes and divides into two different but similar sets of nuclei is known as mitosis. The chromosomes are pulled apart by a mitotic spindle, which is a specialized structure consisting of microtubules.

Cytokinesis

In this phase, the cytoplasm of the cell divides. It begins as soon as the mitosis ends. Plant cells are much tougher than animal cells, as they have a rigid cell wall and high internal pressure. Thus, cytokinesis occurs in plant and animal cells differently.




 

Comments

Post a Comment

Popular posts from this blog

Difference between Prokaryotic cell and Eukaryotic cell, Differences Between Plant Cell and Animal Cell ,Fluorescence microscope principle ,ray diagram and instrumentation

-
Image
krish creations   1.)  Difference between Prokaryotic cell and Eukaryotic cell. Prokaryotic cells are primitive cells mainly found in the unicellular organisms, and they do not nucleus, instead they contain a fragment of DNA, and the organelles are not bounded by the membranes, where as the eukaryotic cells are found in all types of multicellular organisms such as plant and animal cells and they contains nucleus and membrane bound organelles. Prokaryotic cells Eukaryotic cells This cells are always unicellular Eukaryotic cells are present as either unicellular or multicellular. The size of cell is generally range from 0.2 micrometers to 2.0 micrometers in diameter Eukaryotic cells range from 10 to 100 micrometers in diameter. In prokaryotic cells, the cell wall is present and it is very complex in nature. Eukaryotic cells have cell walls very rarely, if present they have simple chemical nature. In this cells true nucleus absent, instead nucleotide is present True nucleus is present. DN
Read more

biology fat answers by krish

-
Image
krish creations " module-1     click here   : module-2     click here   module-3  1.     1.)   Outline the classification of proteins based on the polarity and how are they further classified based on the presence of the R-groups present in the amino acid structure?  click here for answer 2.       2.) What determines the structure and function of the proteins? click here for answer 3.      3.) Fill in the following table with ‘Y’ to indicate ‘yes’ and ‘N’ to indicate ‘no’ for each box as it pertains to each listed amino acid in each category. Some of the names are given only as their three-letter abbreviations. Amino Acid Nonpolar Polar Acidic Side Chain Basic Side Chain Essential? Proline  Y  N  N  Y  N Cys  Y  N  Y  N  N Asp  N  Y  Y  N  N Serine  N  Y  Y  N N  Gln  N  Y  N Y   N 1.        4.  Name the four different types of interactions responsible for               creating tertiary structures in proteins and elaborate the     
Read more

module 1

-
  Module 1: 1.      Anton van Leeuwenhoek made an essential contribution to the development of the cell theory. Elaborate his contribution to the scientific community.  click here 2.      The tree of life was produced by comparing Genetic Sequence Data, and can you make a tree of life with the domain of bacteria, archaea, and eukarya. click here 3.      Water is denser as a liquid than as a solid. Can you explain why and how? click here 4.      Can simple molecules and kinetic energy lead to chemical evolution? Elaborate what experiment supports this hypothesis and infer your results for the same. click here 5.      The prebiotic soup model of chemical evolution is a well-accepted model for the development of life on earth. Do you agree with this hypothesis? If it is yes, justify your answer. click here 6.      When H 2 and CO 2 react, acetic acid can be formed spontaneously while the production of formaldehyde requires an input of energy. What do you infer from this rea
Read more