2.6 Cell Division (Spec)

Question 1

Interphase

Answer 1

Interphase:
- G1 : 
First growth phase
Main functions executed
Organelles replicated
Size increased
- G1 Checkpoint:
Cell size
Growth factors
- S:
DNA replication
- G2:
Second growth phase
Main functions executed
Any unreplicated organelles replicated
Size increased
- G2 Checkpoint:
Cell size
Growth factors
DNA replication & errors

Question 2

Mitosis

Answer 2

Prophase:
Nuclear envelope dissolves
Chromosomes condense (visible under microscope)
Metaphase:
Miotic spindle forms
Centrioles/spindle attach to centromere and centrosome
Chromosomes aligned along equator
Metaphase checkpoint:
Spindle assembly correct?
Anaphase:
Spindle fibres shorten 
Centromeres divided
Chromatids pulled to opposite poles
Telophase:
Nuclear envelope reforms around chromatids

Question 3

Cytokinesis

Answer 3

Cell-surface membrane invaginates

Fuses to form two identical daughter cells

Question 4

Mitosis functions

Answer 4

Growth
Repair
Replacement
Asexual reproduction

Question 5

Meiosis I process

Answer 5

Prophase I:
Nuclear envelope dissolves
Chromosomes condense
Crossing over occurs
Snapping at chiasmata -> recombinant chromosomes
Metaphase I:
Recombinant chromosomes independently assorted at equator
Spindle fibres attached to centromeres and centrosome
Metaphase checkpoint:
Spindle assembly correct?
Anaphase I:
Spindle fibres shorten
Recombinant chromatids pulled to opposite poles
Telophase I:
Nuclear membrane reforms and chromosomes uncoil
Cytokinesis occurs
Diploid -> haploid

Question 6

Meiosis II process:

Answer 6

Prophase II:
Chromosomes condense, become visible
Nuclear envelope breaks down
Metaphase II:
Individual chromosomes assemble at equator, independent assortment and variation increased
Anaphase II:
Individual chromosomes pulled to opposite poles
Spindle fibres shorten
Telophase II:
Chromosomes -> chromatin
Nuclear envelope reforms
Nucleolus visible
Reduction division
Genetically different

Question 7

Differentiation mechanism

Answer 7

Gene expression during DNA replication

Question 8

Stem cell types

Answer 8

Totipotent: Differentiate into all tissue types including placental cells
Pluripotent: Differentiate into all tissue types excluding placental cells
Multipotent: Differentiate into range of cells within specific tissue type