2.2: GENETIC INFORMATION IS COPIED AND PASSED ONTO TO DAUGHTER CELLS Flashcards
(32 cards)
What are the phases of interphase?
- G₁ phase (Gap 1)
- S phase (Synthesis)
- G₂ phase (Gap 2)
What happens during G₁ phase (Gap 1) [3]
- Cell grows.
- New organelles and proteins are made.
- Normal cell functions happen (e.g. respiration, protein synthesis).
What happens during S phase (Synthesis) [2]
- DNA replication occurs.
- Each chromosome duplicates to form two identical sister chromatids.
What happens during G₂ phase (Gap 2) [3]
- Cell continues growing.
- Checks and repairs DNA for any errors.
- Organelles needed for cell division are produced
What happens during prophase? [5]
- Chromosomes condense (become visible).
- Each chromosome has two sister chromatids joined at the centromere.
- Nuclear envelope breaks down.
- Centrioles move to opposite poles of the cell.
- Spindle fibres form from the centrioles.
What happens during metaphase? [2]
- Chromosomes line up at the cell equator.
- Spindle fibres attach to the centromere of each chromosome.
What happens during anaphase? [3]
- Spindle fibres contract.
- Sister chromatids are pulled apart to opposite poles.
- Once separated, each chromatid is now called a chromosome.
What happens during telophase? [4]
- Chromosomes de-condense (become invisible again).
- New nuclear envelopes form around each set of chromosomes.
- The cell now has two nuclei.
When does cytokinesis occur?
After mitosis.
What happens during cytokinesis? [2]
- Cytoplasm divides.
- Two genetically identical daughter cells are formed.
Advantages of Mitosis. [3]
- Growth: It allows multicellular organisms to grow by increasing the number of cells
- Repairs damaged cells
- Produces genetically identical offsprings (allows asexual reproduction)
Difference between animal cells and plant cells in Prophase.
Plant cells have no centrioles and spindle fibres are formed from the cytoplasm.
Animal cells have centrioles which form spindle fibres.
Difference between animal cells and plant cells in cytokinesis.
In plant cells, cell plate forms to create a new cell wall.
In animal cells, cleavage furrow forms and splits the cell.
How does mitosis assist with tissue repair?
Produces identical cells to replace damaged or dead cells.
What can happen if mitosis becomes uncontrolled?
Tumour formation, which may lead to cancer.
What is a proto-oncogene?
A gene that promotes cell division; can mutate into an oncogene causing uncontrolled division.
What is a tumour suppressor gene?
A gene that inhibits cell division; if a mutation occurs it can stop this control, allowing cancer to develop.
Difference between benign and malignant tumours?
- Benign: stays localised.
- Malignant: invades tissues and can spread to other sites.
What is the overall purpose of meiosis?
To produce 4 genetically different haploid gametes for sexual reproduction.
How many divisions occur during meiosis?
Two divisions: meiosis I and meiosis II.
What happens before meiosis starts?
DNA replication during interphase to produce sister chromatids.
What happens in prophase I?
Chromosomes condense; homologous chromosomes pair up (bivalents); crossing over occurs; nuclear envelope breaks down; spindle forms.
What happens in metaphase I?
Homologous chromosomes (bivalents) align at the equator; independent assortment occurs.
What happens in anaphase I?
Homologous chromosomes are pulled to opposite poles; sister chromatids remain attached.
