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OCR Biology A - 2.1.6 - Cell Division, Cell Diversity and Cellular Organisation Part 1

Biology25 CardsCreated about 1 month ago

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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TermDefinition
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