Back to AI Flashcard MakerBiology /OCR Biology A - 2.1.6 - Cell Division, Cell Diversity and Cellular Organisation Part 1
OCR Biology A - 2.1.6 - Cell Division, Cell Diversity and Cellular Organisation Part 1
This flashcard deck covers key concepts in cell division, cell diversity, and cellular organization, focusing on the phases of the cell cycle and mitosis.
What’s in interphase
G1
S
G2
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Key Terms
Term
Definition
What’s in interphase
G1
S
G2
G0
Cell has left cell cycle:
To differentiate
Apoptosis
Senescence
Senescence
Cells no longer divide
Checkpoints in cell cycle
At G1
At G2
Why are there checkpoints
To prevent uncontrolled division that would lead to tumours
To detect and repair damage to DNA
M phase
Checkpoint chemical triggers condensation of chromatin
Cell growth stops
4 stages of mitosis
Cytokinesis then occurs
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| Term | Definition |
|---|---|
What’s in interphase | G1
S
G2 |
G0 | Cell has left cell cycle:
To differentiate
Apoptosis
Senescence |
Senescence | Cells no longer divide |
Checkpoints in cell cycle | At G1
At G2 |
Why are there checkpoints | To prevent uncontrolled division that would lead to tumours
To detect and repair damage to DNA |
M phase | Checkpoint chemical triggers condensation of chromatin
Cell growth stops
4 stages of mitosis
Cytokinesis then occurs |
G1 | Cells grow
Transcription of genes to make RNA occurs
Synthesis of biological molecules occur e.g. protein synthesis |
S phase | DNA replicates (doubles)
Each chromosome has two sister chromatids
Once the cell has entered this phase, it is committed to completing the cell cycle |
Why does S phase happen very rapidly | Exposed DNA base pairs are more susceptible to mutagens so this phase happens quickly to reduce the chances of mutations |
G2 | Cells grow
Chemicals stimulate histones and formation of the spindle
Organelles duplicate |
Prophase | Chromosomes condense
Centrioles duplicate and move to opposite poles
Mitotic spindle begins to form
Nuclear envelope breaks down
Nucleolus no longer visible |
Metaphase | Chromosomes align at equator and attach by their centromeres
Two sister chromatids of each chromosome are attached to spindle fibres |
Anaphase | Centromere splits
Sister chromatids separate from each other and are pulled towards opposite poles of the cell due to spindle fibres shortening (now chromosomes) |
Telophase | Chromosomes decondense
Spindle disappears
Nuclear envelope reforms and a nucleolus reappears |
Cytokinesis in an animal cell | An actin ring around the middle of the cell pinches inwards, creating an indentation called the cleavage furrow |
Cytokinesis in a plant cell | The cell plate forms down the middle of the cell, creating a new wall that partitions it in two |
Where does mitosis occur in plants | Roots
Shoots |
Prophase I | Starting cell is diploid
Homologous chromosomes pair up and exchange fragments (crossing over of non-sister chromatids) |
Metaphase I | Homologue pairs line up at the metaphase plate
The orientation of pairs is random |
Anaphase I | Homologues separate to the opposite ends of the cell
Sister chromatids stay together |
Telophase I | Newly forming cells at haploid
Each chromosome has 2 non-identical sister chromatids |
Prophase II | Chromosomes condense
Spindle fibres begin to capture chromosomes |
Metaphase II | Chromosomes line up individually along the equator |
Anaphase II | Independent segregation of sister chromatids to opposite ends of the cell |
Telophase II | New forming gametes are haploid
Each chromosome has just one chromatid |