Chapter 2.6 Cell Division Flashcards
What happens in Interphase?
First stage of mitosis where chromosomes replicate
What is the longest stage of the cell cycle?
Interphase
Outline the G1, S and G2 phases.
G1: Cell grows larger and organelles synthesised
S: Complete DNA replication
G2: Organelles grow and preparation for mitosis
When do the G1, S and G2 phases occur?
In Interphase
What is the purpose of the G1 and G2 checkpoints?
G1: Checks that correct chemicals are present
G2: Checks that DNA has been replicated correctly
What’s the G0 phase?
After cells have differentiated and cannot differentiate again
Mitosis: Outline what happens in Prophase.
Chromosomes become more distinct, nucleolus becomes less prominent, centriole divides, chromosomes consist of two chromatids joined by centromere and nuclear envelope breaks down
Mitosis: Outline what happens in Metaphase
Each centriole is at a pole, centrioles produces spindle fibres, chromosomes line p at equator and spindle fibres attach to centromere
Define: Centrioles, Centromere and Spindle fibres
Centrioles: Cylindrical organelles that release spindle fibres
Centromere: Links a pair of sister chromatids together during cell division
Spindle fibres: Form a protein structure that divides the genetic material in a cell
Mitosis: Outline what happens in Anaphase.
Centromeres divide into two - chromatids pulled to opposite sides of the cell
Mitosis: Outline what happens in Telophase.
Daughter chromatids reach opposite sides of cell, cytoplasm begins to split, spindles fibres disappear and nuclear envelop + nucleolus begin to reform
Mitosis: Outline what happens in Cytokinesis.
Cell divides
Animal cells: Starts by constriction of edges
Plant cells:
Cell wall is laid down first
What does Mitosis produce?
Two genetically identical daughter cells (diploid)
Define homologous pairs
Two chromosomes in a pair - one inherited from the father and one from the mother creating a bivalent
Meiosis: Outline Prophase I
Chromosomes of the same homologous form bivalents - in a human cell there will be 23 bivalents,
Chromatids of one bivalent cross over
Define ‘crossing over’
Where chromatids join at the chiasmata and exchange information
Meiosis: Outline Metaphase I
Centrioles move to opposite poles and spindle fibres attach to centromeres, bivalents line up across equator
What protein are spindle fibres made from?
Tubulin (meiosis and maybe mitosis)
Meiosis: Outline Anaphase I
Chromosomes pulled to opposite poles and separated into haploid sets
Define haploid
A cell that contains a single set of chromosomes
Meiosis: Outline Telophase I
Nuclear envelope reforms,
Cytokinesis of cytoplasm, chromosomes haploid
Meiosis: Outline Prophase II
Nuclear membranes break down, Centrioles move to opposite poles, Spindle fibres form and chromosomes shorten and thicken
Does prophase II occur in plant cells?
No
Meiosis: Outline Metaphase II
Chromosomes line up at equator, spindle fibres attach chromosomes to centromeres
Meiosis: Outline Anaphase II
Centromeres divide,
Spindle fibres contract and pull chromosomes to opposite poles
Meiosis: Outline Telophase II
Nuclear membranes reform, spindle fibres break down, centrioles reform - produces 4 haploid cells
In meiosis, how can variation occur?
Crossing over (prophase I),
Random assortment (metaphase I), Independent assortment (metaphase II), Production of haploid gametes that fuse randomly, mutations
Define the difference between random and independent assortment
The law of independent assortment covers how the alleles of different genes assort into gametes, and the law of random assortment covers how alleles of the same gene assort into different gametes
What are diploid cells used for?
Tissue growth etc
What are haploid cells used for?
Reproduction - gametes
