Topic 2 - Cell Division Flashcards
Explain the stages in interphase
G1 = cell grows a new organelles that are and proteins are made
S = cell replicates DNA
G2 = growth and proteins for cell division are made
Describe mitosis
Mitosis is the part of the cell cycle in which eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication.
Describe the structure of chromosomes in mitosis
Beginning = two strands (chromatids) joined by centromere, two sister chromatids
End = new chromatids end up as one strand chromosomes in the new daughter cells
What is mitotic index?
The portion of cells that undergo mitosis
What happens in interphase?
Interphase is the first stage of the cell cycle, during which the cell grows and replicates its DNA in preparation for division.
What is the role of spindle fibres in mitosis?
Mitotic spindle, present at the poles of the cells, is a structure made of spindle fibres.
Its role is to separate the chromosomes. The spindle fibres attach to chromosomes during metaphase and pull the chromatids towards opposite poles during anaphase.
What happens if mitosis is uncontrolled?
Uncontrolled cell division can lead to the formation of tumours and of cancers. Many cancer treatments are directed at controlling the rate of cell division.
Explain the process of binary fission
1) The single, circular DNA molecule undergoes DNA replication.
2) Any plasmids present undergo DNA replication.
3) The parent cell divides into two cells, with the cytoplasm roughly halved between the two daughter cells.
4) The two daughter cells each contain a single copy of the circular DNA molecule and a variable number of plasmids.
Describe the process of viral replication
1) Attachment - the virus attaches to the host cell through specific binding between viral proteins and host cell receptors.
2) Penetration and uncoating - After attachment, viruses penetrate the host cell and fuse with the cell membrane. Once inside, the viral capsid is removed (uncoating), releasing the viral nucleic acid.
3) Synthesis of viral components - Viral DNA enters the host cell’s nucleus for replication, using the host’s DNA polymerase enzymes. RNA viruses replicate in the cytoplasm, often using their own RNA-dependent RNA polymerase as host cells do not naturally contain this enzyme. Viral mRNA is used to make viral proteins by the host’s ribosomes.
4) Assembly and maturation - New viral particles are assembled from the newly synthesized nucleic acids and proteins.
5) Release - Newly formed viruses exit the host cell to infect new cells. This can occur through lysis (bursting the cell) or budding (enveloped viruses), where the virus acquires its envelope from the host cell membrane.
What happens in prophase?
- Chromosomes condense
- Chromosomes move towards opposite poles
- Spindle fibres begin to emerge from centrioles
- Nuclear envelope breaks down into small vesicles
What happens in metaphase?
- Centrosomes reach opposite poles
- Spindle fibres continue to extend from centrosomes
- Chromosomes line up at the equator of the spindle
- Spindle fibres attach to centromeres
What happens in anaphase?
- Sister chromatids separate at the centromere
- Spindle fibres shorten
- Separated sister chromatids are pulled to opposite poles by the spindle fibres.
What happens in telophase?
- Chromosomes begin to decondense
- Nuclear envelope begin to reform
- Spindle fibres break down
