Unit 1 - AOS 1 - Mitosis and cell cycle Flashcards
The functions of cell division
- Asexual reproduction for unicellular organisms
- Asexual reproduction for multicellular organisms
- Sexual reproduction in multicellular organisms
- Growth and development of a multicellular organisms
- Repair and maintenance of a multicellular organism
Define Binary fission
Is cell division completed asexually by prokaryotes, that results in two genetically identical organisms.
3 types of asexual reproduction for multicellular organisms
- Budding: they produce growths from their bodies which eventually fall off and become cloned offspring (hydra)
- Autonomy: when an organism performs self amputation of one of its body parts (starfish)
- Vegetative reproduction: one way is through cell division to produce runners. Which are extensions from the parent plant that contain attached cloned offspring. (Spider and strawberry)
In sexual reproduction (multicellular) , cell division is required for two reasons …
- To make gametes like speed and ova
- To allow the multiple divisions needed to create a multicellular organism
Definition of cell cycle
This represents the processes that occur between one cell division and the next cell division in a cells life
3 main stages of the cell cycle
- interphase
- mitosis
- cytokinesis
Interphase definition
The cell spends most of its life Performing it’s specialised sunrooms and then prepares for cell division when the time comes
Parts of the interphase are …
- G1
- Synthesis
- G2
What happens in the G1 phase of the Interphase ?
- the cell grows after cell division to reach to full size (can double)
- the cell performs it’s specialised function depending on what type of cell it is.
- this is the longest part of the cell cycle for most cells
Explain what happens to cells that stop dividing
- these cells stop progressing through the cell cycle and go into the G0 (gap zero)
- they simply continue there specialised function until they die
- e.g muscle cell, heart muscle cell, Brain cell
What happens in the synthesis phase of the interphase
- the DNA is replicated creating two identical copies of each chromosome
- the centriole pair also duplicates to create two pairs
Function of centriole
They are involved in the development of spindle fibres used during cell division
What happens in the G2 phase of the Interphase
- prepares for mitosis through rapid growth of cytoplasm
- the cell increases the synthesis of the proteins needed to make the spindle fibers used in mitosis
- DNA is checked for replication errors that may have occurred during DNA replication in S phase.
Definition of mitosis
The process that sorts and divides the duplicated chromosomes into two identical sets of DNA so that each daughter cell get’s one set.
how many chromosomes do humans somatic cells have before replication and after replication?
46 –> 92
what are somatic cells?
Are body cells (excluding sex cells)
Definition of cytoinesis
Process that divides the cytoplasm in half to create two separate daughter cells.
Cytokinesis –> Animal cells
- A cleavage furrow is formed
- to constrict the cell membrane in the middle of the cell and divide it
Cytokinesis in plant cells
- Cell wall make cytokinesis challenging
- Cell plate is created in middle of cell which is made from vesicles, containing material needed to build the cell wall.
- Vesicles join to create new cell wall in the midline of the cell separating the 2 daughter cells.
Chromatin defiition
- Is the duplicated chromosomes before they are condensed
- long and thin
Sister chromatids
- The 2 identical sides of each duplicated chromosome
Centromere definition
Is what connects the 2 chromotids
Kinetochores definition
is a protein structure that assemble on either side of the centromere.
- they are the sites of attachement for the microtubules/spindle fibres, which pull the sister chromotids apart.
Centrosome
The centriole pair along with the surrounding proteins form the organelle centrosome.
- responsible for organizing microtubules
- Only found in animal cells
Prophase (mitosis)
- Centrosomes migrate to opposite ends of the cell
- Spindle fibers begin to form
- nucleur envelope begins to dissolve
- Chromatins begin to condense
- Nucleolus begins to disappear
Pro-Metaphase (mitosis)
- Nuclear membrane is almost completely dissolved –> spindle fibers access to duplicated chromosomes
- Nucleolus has disappeared
- Kinetochore spindle fibers attach to kinetochore of chromosomes and begin to line them up on equatorial plate
- Polar spindle fibers extend from opposite ends and push against each other –> elongating the cell
- Astral spindle fibers help anchor the centrosomes at opposite poles
Metaphase (mitosis)
- Centrosomes fully migrated
- Spindle fibres completely formed
- Nuclear membrane completely dissolved
- Chromosomes are lined up on equatorial plate
Anaphase (mitosis)
- Kinetochore spindle fibers shorten –> pulling sister chromatids apart
- Polar spindle fibers push against each other even more elongating the cell
- Each chromatid becomes its own chromosome
Telophase (mitosis)
(reverse of prophase)
- Spindle apparatus disassemble
- Chromosomes de-condense and become chromatins
- Nuclear membrane begins to reformulate
- Nucleolus appears
- Cleavage furrow (animals) or Cell Plate (Plants) begins to form signaling the beginning of cytokinesis
Cells that undergo Binary fission and mitosis?
Binary fission = Prokaryotic cells
Mitosis = Eukaryotic cells
When are the 3 checkpoints in the cell cycle?
G1, G2, Spindle checkpoint (metaphase)
G1 checkpoint
- Cell checks it has grown large enough to divide
- Cell checks to see if DNA is undamaged and enough nutrients are present
G2 checkpoint
- Checks to see if DNA replication is finished and no mistakes
