The Cell Cycle Flashcards
Why is mitosis important?
- Growth, replacement and repair of tissues in multicellular organisms.
- Also necessary for asexual reproduction, which is the production of genetically identical offspring from one parent in multicellular organisms.
What is mitosis?
The process of nuclear division by which two genetically identical daughter nuclei are produced and also genetically identical to parent cell.
What happens in prophase in mitosis?
- Chromosomes condense and now visible when stained.
- The two centrosomes move towards opposite poles.
- Spindle fibres begin to emerge from the centrosomes.
- Nuclear envelope breaks down into small vesicles.
- Nucleolus disappears.
metaphase in mitosis
- each centrosome reaches a pole
- centrosomes organise spindle fibres -chromosomes line up on equator attached by spindles to centromere
Anaphase in mitosis.
-chromosomes split at centromere
- chromatids move to opposite poles centromere first
- chromatids are pulled apart.
Telophase of mitosis.
- nucleolus reforms
- nuclear envelope reforms
- spindle breaks down
-chromatids decondense - cytokinesis (division of cytoplasm py constriction)
Prophase 1 in meiosis.
- DNA condenses.
- nucleolus breaks down
- nuclear membrane breaks down
- centrioles move to poles
- Crossing over may occur at chiasmata, as sister chromatids are close to each other. This causes alleles to swap places, which causes genetic variation.
How are chromosomes arranged in prophase 1 in meiosis and what is this called?
- Chromosomes are arranged side by side in homologous pairs.
- Pair of homologous chromosomes is called bivalent.
What happens in metaphase 1 in meiosis?
- Bivalents line up along equator of the spindle.
- Maternal and paternal chromosomes in each pair position themselves independently of the others; this is independent assortment.
What happens in anaphase 1 in meiosis?
- Homologous pairs are separated, spindle fibres contract.
- Microtubules pull chromosomes to opposite ends.
- Centromeres do not divide.
Telophase 1 in meiosis.
- Chromosomes arrive at opposite poles.
- Spindle fibres start to break down.
- Nuclear envelope forms around two groups of chromosomes and nucleoli reforms.
prophase 2 is meiosis
- Nuclear membrane breaks down.
- Chromosomes condense.
Metaphase 2 in meiosis.
- Chromosomes line up in a single line along equator of spindle.
Anaphase 2 in meiosis.
- Centromeres divide.
- Chromatids pulled to opposite poles.
- 4 groups of chromosomes created that have half n. of chromosomes compared to original parent cell.
What happens after anaphase 2 in meiosis?
Cytokinesis creates 4 haploid cells.
What is cytokinesis?
Division of cytoplasm.
How does cytokinesis occur in animal cells?
- The cell surface membrane pinches inwards creating a cleavage furrow in middle of cell, which contracts, dividing cytoplasm in half.
How does cytokinesis occur in plant cells?
- Vesicles from the golgi apparatus gather along equator of spindle.
- Vesicles merge with each other to make form new cell surface membrane and also secrete layer of calcium pectate which become middle lamella.
- End product of cytokinesis is meiosis 1 is two haploid cells.
What happens in G1 in interphase?
-first growth stage
- protein syninesis
- Organene synthesis
What does G1 checkpoint check for?
- Cell size
- Nutrients
- Growth
- Damage
What happens in G0?
- Resting
- If cell hasn’t reached G1 criteria.
- Due to damage/ limits.
synthesis in interphase.
- DNA synthesis.
- Chromosomes are checked to ensure they have been replicated.
- If replication not successful, cycle stops.
What happens in G2 in interphase?
- Rapid cell growth.
- Molecules for cell division synthesised.
- Cycle delayed for any repair.
What does G2 checkpoint check for?
- Cell size.
- Replication.
- Damage.
- Chromosome attachment.
