3.7 Mitosis Flashcards
Describe the stages of the cell cycle in euk cells
- Interphase
- Mitosis
- Cytokineses
What is interphase
The DNA replicates leading to 2 chromatids joined at the centromere
Number of organelles and volume of cytoplasm increases and protein synthesis
What is mitosis
The nucleus divides to produce 2 nuclei with identical copies of DNA produced by the parent cell
What is cytokineses
Cytoplasm and cell membrane divides to form 2 new geneticallyi identical duaghter cells
Name the 4 stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
What happens in stage 1 of mitosis (3)
- Prophase: Chromosomes condense, becoming shorter and thicker
-They also appear as 2 sister chromatids joined by a centromere - Nuclear envelope breaks down
- Centrioles move to oppoiste poles forming spindle network
What happens in stage 2
- Metaphase:Spindle fibres attatch to chromosomes by their centromeres
- Chromosomes align along the equator
What happens in stage 3 of mitosis
- Anaphase:Spindle fibres shorten and contract
- Centromere divides
- pulling chromatids to opposite poles of the cell
What happens in stage 4 of mitosis
- Telophase: Chromosomes uncoil beocming longer and thinner
- Nuclear envelopes reform making two nuceli
- Spindle fibres and centrioles break down
Describe how prok cells replicate (3)
Through binary fission:
*Replication of circular DNA
* Replication of plasmids
* Divison of cyroplasms to produce two daughter cells
-Single copy of circular DNA
-Variable number of copies of plasmids
Why do some Euk cells not undergo the cell cycle
WIthin multicelluar organisms, not all cells retain the ability to divde_e.g. neurons)
Only cells that do retain this ability go through a cell cycle
Nuerons do not have centrioles
What is the importance of Mitosis in the life of an organism
Parent cell dvides to produce 2 genetically identical daughter cells for:
* Growth of multicellular organisms by increasing cell number
Replacing Cells to repair damaged tissues
Asexual reproduction
Describe how viruses replicate (4)
Being non living, viruses do not undergo cell division:
* Attatchment proteins attatch to complimentary receptors on host cell
* They inject viral nucleic acid (DNA/RNA) into host cell
* Infected host cell replicates virus particles such as nucelic acid viral proteins/ enzymes
* virus is then assmebled and then released
Explain how Prophase can be identified
Chromosomes are visible bevcause they are condensing
They are randomly arrnaged due to no spindle activity
Explain how metaphase canb be identifed
Chromosomes are lined up on the equator of the cell as they are attching to a spondle fibre
