Cell Divison Flashcards
Not all multicellular organisms retain the ability to divide
What are they able to divide using instead?
Cell cycle
Where does DNA replication occur during the cell cycle
Interphase
Define mitosis
-Part of the cell cycle in which eukaryotic cells divide
- they produce 2 daughter cells
- each with identical copies of DNA produced by parent cell during DNA replication
What are the 3 key stages of the cell cycle
- interphase -G1,S,G2
- nuclear division - mitosis - meiosis
- cytokinesis
What is the G1 phase
Proteins r are synthesised for replication
Number of organelles & volume of cytoplasm increases,
What is the s phase - synthesis
● DNA replicates semi-conservatively (S phase)
○ Leading to 2 chromatids (identical copies) joined at a centromere
What is the G2 phase - gap phase 2
● Number of organelles & volume of cytoplasm increases, protein synth
What is interphase known as
Resting phase
What is nuclear divisor
It is mitosis -
Nucleus divides
To produce 2 nuclei with identical copies of DNA produced by parent cells
What is cytokinesis
Cytoplasm and cell membrane divides
To form 2 new genetically identical daughter cells
What are the 4 key stages of mitosis
- Prophase
- metaphase
-anaphase - telophase
What are 4 key facts of mitosis
- One round of Divison
- genetically identical cells are made
- diploid Cells are made
_ growth And repair
What is an example of growth and repair in mitosis
Clonal expansion of B cells
What is the difference between the cell cycle And mitosis
Cell cycle includes growth period between divisions
Mitosis is only 10% of the cell cycle and refers to nuclear division
Outline what happens during the prophase
● Chromosomes condense, becoming shorter / thicker so visible
○ Appear as 2 sister chromatids joined by a centromere
● Nuclear envelope breaks down
● Centrioles move to opposite poles forming spindle network
- spindle fibers start to attach to chromosomes by their centromere
Outline what happens during the metaphase
● Spindle fibres attach to chromosomes by their centromeres
● Chromosomes align along equator
Outline what happens during anaphase
● Spindle fibres shorten / contract
● Centromere divides
● Pulling chromatids (from each pair) to opposite poles of cell
Outline what happens in the telophase
● Chromosomes uncoil, becoming longer / thinner
● Nuclear envelopes reform = 2 nuclei
● Spindle fibres / centrioles break down
What is the equation of mitoxic index
The number of cells in mitosis/ total number of cells X 100
Define mitotic index
Proportion of cells in a population undergoing mitosis
What does a higher proportion of mitotic index mean
More cells are undergoing all divisor
True or false mitosis a controlled process
True
Describe how tumours and cancers form
Mitosis is a controlled process so:
● Mutations in DNA / genes controlling mitosis can lead to uncontrolled cell division
● Tumour formed if this results in mass of abnormal cells
○ Malignant tumour = cancerous, can spread (metastasis)
○ Benign tumour = non-cancerous
Suggest how cancer treatments control rate of cell division
● Some disrupt spindle fibre activity / formation
○ So chromosomes can’t attach to spindle by their centromere
○ So chromatids can’t be separated to opposite poles (no anaphase)
○ So prevents / slows mitosis
● Some prevent DNA replication during interphase
○ So can’t make 2 copies of each chromosome (chromatids)
○ So prevents / slows mitosis
What is the division in prokaryotic cells
Binary fission
What is the process of binary fission
- Replication of circular DNA And plasmids
-division of cytoplasm to produce 2 daughter cells
-each with a single copy of circular DNA and a variable number of copies of plasmids
Why don’t viruses undergo cell division and what happens instead
-As they’re non-living
- they inject their nucleic acid into the host
Infected host cell replicates the virus particle
-
Name the fixed poison occupied by a gene on a DNA molecule
Locus
Describe how viruses replicate
- Attachment proteins attach to complementary receptors on host cell
Inject viral nucleic acid (DNA/RNA) into host cell
Infected host cell replicates virus particles:
a. Nucleic acid replicated
b. Cell produces viral protein / capsid / enzymes
c. Virus assembled then released
- Attachment proteins attach to complementary receptors on host cell
