3.2.2 (cell replication) Flashcards
(16 cards)
Which part of the cell cycle is mitosis?
When the nucleus divides to form 2 identical daughter nuclei
Do all cells in multicellular organisms retain the ability to divide?
No
What do eukaryotic cells that retain the ability to divide show?
A cell cycle
What could uncontrolled mitosis lead to and how does this link to the treatment?
Formation of tumours and cancer
Many cancer treatments aim to control the rate of cell division
When does DNA replication occur?
During the interphase of the cell cycle
Describe interphase
Semi conservative replication of DNA
Each chromosome now two identical sister chromatids joined at the centromere
Chromosomes not visible- long, stringy, decondensed form
Cell growth
Describe prophase
Chromatid pairs become visible
Chromatids condense- shorter and fatter
Spindle assembled in cytoplasm
Nuclear envelope breaks down
Centrioles move to opposite poles of cell
Describe metaphase
Spindle fibres attach to chromatid pairs at centromere
Chromatid pairs line up along equator of cell
Chromatids face opposite poles of cell
Describe anaphase
Centromeres divide
Spindle fibres contract pulling chromatids apart
Separated chromatids now called chromosomes- pulled towards poles
Describe telophase
Chromosomes arrive at poles
Chromosomes unwind- thinner and longer so no longer visible
Nuclear membrane reforms
Mitosis is complete
Describe cytokenisis
Infolding of cell membrane in middle of cell
Cell divides- 2 genetically identical daughter cells are produced
How can the stages of mitosis be identified?
Interphase- chromosomes not visible
Prophase- chromosomes become visible
Metaphase- chromosomes line up along equator of cell
Anaphase- chromosomes move to poles of cell
Telophase- nucleus has divided, cell membrane hasnt
How do you calculate %mitotic index?
(number of cells in mitosis/total number of cells) x 100
Describe binary fission
Circular DNA replicates and both copies attach to cell membrane
Plasmids also replicate
Cell membrane grows between two DNA molecules and pinches inwards
Cytoplasm divides in two
New cell wall forms dividing the cell into 2 genetically identical daughter cells
Each new cell contains a single copy of circular DNA and variable number of plasmid copies
Describe viral replication
Virus attaches to host cell receptors with attachment proteins on its surface
Virus injects its nucleic acid/ viral RNA into host cell
Host cell can be prokaryotic or eukaryotic
Reverse transcriptase enzyme coverts viral RNA to DNA
Host cell replicates viral particles such as enzymes, nucleic acids and structural proteins
Viral particles assembled in host cell
Cell bursts open releasing virus
Describe how to remember the stages of mitosis
Interphase- introduction
Prophase- prominent (chromosomes become prominent)
Metaphase- middle (chromosomes move to equator)
Anaphase- apart
Telophase- two nuclei
Cytokenesis- conclusion
