Mitosis

mitosis

Basics
Mitosis
Mitosis is a form of cell division in which a “parent” cell duplicates all of its contents to produce two identical “daughter” cells.

Purpose
The purpose of mitosis is asexual reproduction, replacement, growth, and repair of somatic (body) cells.

Phases
As per the image above (from nih.gov), mitosis occurs in phases.


Phases

(1) Interphase
chromosome
Chromosomes (threadlike structures) made up of chromatin containing DNA duplicate within a cell’s nucleus.  Each new copy of a chromosome is called a chromatid.  The chromatids remain attached to each other by a centromere.  DNA (Deoxyribonucleic Acid) is a molecule in the shape of a double helix within chromosomes that contains the genetic material passed down from parent to daughter cells.  A gene is a segment of DNA that codes for a trait (such as eye color).  DNA is the molecular basis of biological heredity/inheritance.

(2) Prophase/Prometaphase
The chromatin of the duplicated chromosomes condenses, the nuclear membrane breaks apart, and centrioles (from centrosomes) divide and move to opposite ends of the cell.  As they get situated, the centrioles help to anchor a spindle of microtubules that start to interact with the chromosomes.

(3) Metaphase
The copied chromosomes align in the middle of the spindle at the equator (central plane) of the cell.

(4) Anaphase
Chromosomes separate into two genetically identical groups and move to opposite ends of the spindle.

(5) Telophase
In this last phase of mitosis, nuclear membranes form around each of the two new sets of chromosomes, the chromosomes begin to spread out, and the spindle begins to break down.

Cytokinesis
Cytokinesis is not a phase of mitosis but is necessary to complete cell division.  In cytokinesis, the cell splits into two identical daughter cells, each with the same number of chromosomes as the parent.  In humans, such cells have two copies of 23 chromosomes—46 chromosomes altogether—and are called diploid.


Practice – Questions

1.  Mitosis is a form of cell division in which a parent cell duplicates all of its contents to produce two identical:
A.  grandparent cells
B.  cousin cells
C.  auntie cells
D.  daughter cells

2.  Mitosis occurs in:
A.  eons
B.  tides
C.  phases
D.  eras

3.  Chromosomes duplicate during:
A.  Interphase
B.  Prophase
C.  Metaphase
D.  Anaphase

4.  Copied chromosomes align in the middle of the spindle during:
A.  Interphase
B.  Prophase
C.  Metaphase
D.  Anaphase

5.  The last phase of mitosis is:
A.  Interphase
B.  Telophase
C.  Prophase
D.  Cytokinesis


Practice – Answers

1.  D.  daughter cells

2.  C.  phases

3.  A.  Interphase

4.  C.  Metaphase

5.  B.  Telophase

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