3 Cell Division Flashcards
Homologous chromosomes
46 chromosomes
23 pairs
Homologous pairs
Same genes ; same size ; same shape
Diploid Human v Haploid
Diploid human has 46 chromosomes
- 2 copies of each chromosome
Haploid sperm and egg haves 23 chromosomes.
- 1 copy of each chromosome
When are individual chromosomes visible?
Only when they are supercoiled.
How many chromosomes in a brain cell v egg cell?
64
32
What are Gametes and Alleles?
Alleles are alt versions of the same gene
Gametes are sex cells either sperms or eggs.
Phases of the cell cycle?
Interphase
G1 - cell increases in mass
S phase - DNA synthesis
G2
Mitosis
Cytokinesis.
How to recognise cells in interphase?
NO visible chromosomes as they are relaxed.
Visible nucleus - nuclear envelope is intact.
How to recognise cells undergoing mitosis?
The nucleus divides in order to create 2 genetically identical nuclei
How to recognise cells in cytokinesis?
Cytoplasm divides to produce 2 genetically identical cells.
What are the 4 phases of Mitosis?
Prophase
Metaphase
Anaphase
Telophase
Features of prophase?
- Centrioles duplicate and move to opposite poles.
- DNA condenses around histone proteins to form duplicated chromosomes
- Nuclear envelope dissolves.
Features of Metaphase?
- Centrioles produce spindle fibres.
- Chromosomes line up at the centre of the cell
- Chromosomes attach to spindle fibres via centromeres.
Features of anaphase?
- Spindle fibres contract.
- Sister chromatids are pulled apart.
- Move to opposite cell poles.
Features of telophase?
- The nuclear envelope reforms around single chromosomes
- DNA unwinds from single chromosomes to reform chromatin
- 2 nuclei are now in one cell.
