Chapter 6 - Cell Division Flashcards
Stages of the cell cycle
Interphase mitotic phase, G0
Stages of interphase
G1, S, G2
G1
Organelles replicate and the cell grows
S
DNA is replicated in the nucleus
G2
The cell continues to grow and energy stores increase
What is the mitotic phase?
Cell division
Consist of mitosis (nuclear division) and cytokinesis (cytoplasm divides)
What is G0
When a cell temporarily or permanently leaves the cell cycle
Due to
Differentiation
Damage DNA/cell death
Where are the checkpoints in the cell cycle?
G1, G2, metaphase
G1 checkpoint
Checks cell size growth and DNA damage
If checks not passed cell goes into G0
G2 checkpoint
Check cell size DNA replication and damage
If checks not passed, problem, is waited out
Metaphase checkpoint
Checks spindle fibre attachment
If checks failed, waited out
Mitosis: prophase
Chromosomes condense nuclear envelope disappears
Mitosis: metaphase
Chromosomes a line along the metaphase plate
Mitosis: anaphase
Centromere divides
sister chromatids separate to opposite poles
spindle fibres contract to pull them apart
Mitosis: Telophase
Chromatids assemble along opposite poles
detach from spindles,
Chromosomes decondense
nuclear envelopes reappear
Significance of mitosis
Asexual reproduction
growth
Replacing of dead /damaged cells
Significance of meiosis
Sexual reproduction
Produces genetic variation
Meiosis: prophase one
Chromosomes condense
Nuclear envelope disappears
Homologous chromosomes pair up (bivalents)
Crossing over of genes occurs
Meiosis metaphase one
Bivalents align at the metaphase plate
Independent assortment (randomly)
Meiosis anaphase one
Homologous pairs of chromosomes are pulled to opposite poles
The centromeres don’t divide
Meiosis telophase one
Nuclear envelope reforms around the chromosomes at opposite poles
Cytokinesis occurs (not part of Telophase)
Meiosis, prophase, two
The nuclear envelopes breakdown and chromosomes condense
Meiosis metaphase two
Chromosomes lineup along the metaphase plate
Meiosis, anaphase, two
Centromere is divide and chromatids are pulled to opposite poles by spindle fibre contraction
