cell division Flashcards
Stage 1
Interphase
● DNA replicates semi-conservatively (S phase)
○ Leading to 2 chromatids (identical copies) joined at a centromere
● Number of organelles & volume of cytoplasm increases, protein synthesis (G1 / G2)
Stage 2
Mitosis
● Nucleus divides
● To produce 2 nuclei with identical copies of DNA produced by parent cell
cytokenesis
● Cytoplasm and cell membrane (normally) divide
● To form 2 new genetically identical daughter cells
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
● SF start to attach to chromosomes by their centromeres
metaphase
● SF attach to chromosomes by their centromeres
● Chromosomes align along equator
anaphase
● Spindle fibres contract
● Centromere divides
● Pulling chromatids to opposite poles of cell
telophase
● Chromosomes uncoil, becoming longer / thinner
● Nuclear envelopes reform = 2 nuclei
● Spindle fibres / centrioles break down
importance of mitosis
growth
replaced damage cells
asexual reproduction
prok replication
- Replication of circular DNA
- Replication of plasmids
- Division of cytoplasm to produce 2 daughter cells
○ Single copy of circular DNA
○ Variable number of copies of plasmids
viral replication
- 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
Describe the general structure of a virus particle
- Nucleic acids surrounded by a capsid
(protein coat) - Attachment proteins allow attachment
to specific host cells - No cytoplasm, ribosomes, cell wall,
cell-surface membrane etc. - Some also surrounded by a lipid
envelope eg. HIV
