Cell & Nuclear Division

Question 1

Define Chromatin

Answer 1

1 DNA molecule coiled around proteins and upon itself, forming a thread like structure

Question 2

Define Chromosome (ChS)

Answer 2

Highly condensed Chromatin, forming a visible structure

Question 3

Define Centromere

Answer 3

Region of ChS that holds 2 sister Chromatids (ChT) together

Question 4

Define Kinetochore

Answer 4

Disc-shaped protein complex of the ChS that allows specific fibres to attach during cell division

Question 5

Define Homologous ChS (HChS) and state its properties

Answer 5

Definition: A pair of ChS with the same Gene Loci, length, shape and determines the same characteristics of the cell

Same Length: Both ChS have genetic coding for the same characteristics at similar loci

Same Centromere Position: ChS can pair with each other during Prophase of Meosis

Question 6

Define Meosis

Answer 6

A type of cell division that occurs in sexually reproducing orgasms to produce Gametes (Sex Cells - Sperm and Eggs in humans)

Question 7

Define Cell Cycle

Answer 7

The period from which a cell is formed by division to the point that the cell divides

Question 8

Describe the Interphase

Answer 8

• DNA in ChT form, uncondensed-> Thread-like, cannot be seen clearly under light microscope

-Preparation for Cell Division -> Cell Growth, DNA Replication, Synthesis of proteins and organelles for Mitosis

Question 9

Describe Cytokenesis

Answer 9

• Cytoplasm divides into 2 parts -> Each enclosed newly formed daughter nucleus and gives rise to 2 separate daughter cells
• [For Plant Cells], cell plate forms new cell walls and splits parent cell into 2 daughter cells

Question 10

Describe Prophase

Answer 10

• ChT condenses and ChS becomes visible
• After DNA replication, ChS are seen to consist of 2 sister Chromatids bound at the Centromere
• [For Animal Cells], Centrioles migrate to opposite ends of the cell
• Nucleolus and Nuclear Envelope breaks down

Question 11

Describe Metaphase

Answer 11

• ChS arrange themselves 90° to spindle axis at the equator of the cell
• Spindle fibers attach to the ChS at their Centromere

Question 12

Describe Anaphase

Answer 12

• Centromere of each ChS divides and sister Chromatids seperate
• Sister Chromatids move to opposite poles of the cell due to the shortening of spindle fibers

Question 13

Describe Telophase

Answer 13

• Sister Chromatids reach their respective poles of the cell and becomes ChS of daughter cells
• ChS uncoils and becomes ChT
• Spindle fibers break down
• Nucleolus and Nuclear Envelope reforms around the ChT at each pole