Genetics Station Flashcards
Purpose of Mitosis
- Passes along identical genetic
information to daughter cells - cell division
Purpose of Meiosis
- Passes along genetic information to
gamete cells in sexually
reproducing organisms - Make haploid cells
How many stages of mitosis?
One stage. (divides only once)
4 phases + Interphase
How many stages of meiosis?
Occurs in two stages.
1. Reduction = cells become haploid
2. Division = cells further multiply
What are the types of cells involved in mitosis?
somatic cells (body cells) of multi-cellular organisms
What are the types of cells involved in meiosis?
Both female and male gametes
Ex. sperm & ova in animals
Ex. pollen & ova in flowering plants
Final outcome of mitosis?
- Produces diploid cells
- Identical to mother cell
Final outcome of meiosis?
- Produces haploid cells
- Not identical to parent cells
How many chromosomes in somatic cells after mitosis?
46
How many chromosomes do human gametes have after meiosis?
23
Mitosis: Prophase
- Chromosomes become visible and attach to spindle fibres
- Centrioles, appear and move to opposite sides of the cell
- The nucleolus disappears and the nuclear membrane starts to dissolve
Mitosis: Metaphase
- Spindle fibres begin moving and aligning the chromosomes at the cell’s equator
- The chromosomes are pulled toward the centre
of the cell - Chromosomes centromeres become aligned at the center of the cell
Mitosis: Anaphase
- Centromeres divide, sister chromatids move to opposite poles of the cell becoming
individual chromosomes
Mitosis: Telophase
- Chromosomes reach opposite poles of the cell
- The spindle fibres dissolve
- Nuclear membranes reform around each set of daughter chromosomes
- RESULT: TWO DAUGHTER NUCLEI!
Interphase
- Increase protein supply
- Create more organelles
- Grow in size
- Duplicating DNA
- Not part of mitosis
- Consists of the G1, S and G2 phases of the cell cycle.
Cytokinesis (follows mitosis)
- The cell membrane pinches inwards
- Final separation of the 2 daughter cells
Meiosis: early prophase I
DNA is doubled
Meiosis: Late prophase I
Chromosome pairs called “Homologous Chromosomes” overlap and carry out “crossover”
Meiosis: Metaphase I
Chromosomes move to the equator of the cell and line up in pairs
Meiosis: Anaphase I
- Homologous chromosomes move to opposite poles
- Chromosome number is halved
- Only one chromosome from each homologous pair will be in the new daughter cells
Meiosis: Telophase I
- Nuclear membrane forms
- Genes are different on the chromosomes of the two nuclei
Crossover
- Creates genetic variation between the gametes
- Occurs during prophase I where genes are shuffled between homologous chromosomes
Meiosis: Prophase II
- Nuclear membrane dissolves
- Spindle fibers form
Meiosis: Metaphase II
Chromosomes line up at the equator and are still attached at the centromere
Meiosis: Anaphase II
- Sister chromatids separate to opposite poles
- Nuclear membranes form around chromatids
Meiosis: Telophase II
Second nuclear division completed and 4 daughter cells formed