3.2.2 - CELL CYCLE + MITOSIS Flashcards
describe binary fission in bacteria (3)
- replication of circular DNA
- replication of plasmids
- division of cytoplasm to produce daughter cells
state the process by which bacteria divide (1)
binary fission
suggest and explain how two environmental variables could be changed to increase the growth rate of cells (4)
any two pairs:
- increased concentration of glucose
- increased respiration
OR
- increased concentration of oxygen
- increased respiration
OR
- increased temperature
- increased enzyme activity
OR
- increased concentration of phosphate
- increased ATP/DNA/RNA
OR
- increased concentration of nucleotides
- increased DNA synthesis
describe the role of spindle fibres and the behaviour of the chromosomes during prophase, metaphase and anaphase (4)
- in prophase, chromosomes condense (shorten and thicken)
- in prophase/metaphase, centromeres of chromosomes attach to the spindle fibres
- in metaphase, chromosomes line up at the equator/centre of the cell
- in anaphase, centromeres divide
what name is given to the division of the cytoplasm during the cell cycle (1)
cytokinesis
the dark stain used on the chromosomes bind more to some areas of the chromosomes than others, giving the chromosomes a striped experience.
suggest one way the structure of the chromosomes could differ along its length to result in the stain binding more in some areas. (1)
any one:
- differences in base sequences
- differences in histones/interactions with histones
- differences in condensation
what is a homologous pair of chromosomes? (1)
two chromosomes that carry the same genes/same loci/genes for the same characteristics
a microbiologist investigated the ability of different plant oils to kill the bacterium Listeria monocytogenes. she cultured the bacteria on agar plates. she obtained the bacteria from a broth culture.
describe two aseptic techniques she would have used when transferring a same of broth culture onto an agar plate. explain why each was important (4)
any two pairs:
- keep lid on Petri dish
- to prevent unwanted bacteria from contaminating the dish/L monocytogenes may get out
OR
- wear gloves/mask/wash hands
- to prevent contamination from bacteria on hands/to prevent spread of bacteria outside the lab
OR
- use sterile pipette
- to maintain a pure culture of bacteria
describe the appearance and behaviour of chromosomes during mitosis (5)
during prophase:
1. chromosomes condense (shorten and thicken), and become visible
2. chromosomes appear as two sister chromatids joined at the centromere
during metaphase:
3. chromosomes line up on the equator of the cell
4. chromosomes attach to the spindle fibres
5. by their centromere
during anaphase:
6. the centromere splits
7. sister chromatids separate and are pulled to opposite poles of the cell
during telophase:
8. chromosomes become longer and thinner
chemotherapy is the use of a drug to treat cancer. the drug kills dividing cells.
more cancer cells could be destroyed if the drug was given more frequently.
suggest why the drug was not given more frequently (2)
- so that more healthy cells would not be killed
- because it would take time to replace these cells
the events that take place during interphase and mitosis lead to the production of two genetically identical cells. explain how (4)
- DNA is replicated
- involving complementary base-pairing
- sister chromatids are identical
- each chromatid is separated to opposite poles of a cell.
bacteria are often used in industry as a source of enzymes. one reason is because bacteria divide rapidly, producing a large number of them in a short time.
describe how bacteria divide (2)
- binary fission
- replication of circular DNA
- division of cytoplasm to produce 2 daughter cells
- each with a single copy of DNA
what is a tumour? (2)
- abnormal cells
- due to uncontrolled cell division/mitosis
describe how you would determine a reliable mitotic index (MI) from tissue observed with an optical microscope (3)
do not include details of how you would prepare the tissue observed with an optical microscope
- count cells in mitosis in field of view
- divide this by the total number of cells in field of view
- repeat this many times
suggest why preventing the formation of spindle fibres stops the cell cycle (2)
- chromosomes cannot attach to the spindle
- so metaphase cannot occur