All Cells Arise From Other Cells Flashcards
Why do you use stain to look at cells?
Provides contrast
Stains chromosomes
Allow to see stage of mitosis
Why are cells squashed to be seen under a microscope?
To allow light to penetrate to make chromosome visible
Why are cells placed in a watch glass full of HCl before looking at under a microscope?
To fix and kill cells
Stops cells dividing so the stay in same stage of mitosis
Make cellulose cell wall more porus so stain absorbed easier
Why is the last 2mm of a root used to study mitosis?
End of root grows by producing more cells (mitosis)
Back of tip grows by elongating cells (less cells per unit area= less mitosis)
What is a mitotic index?
The proportion of cells undergoing mitosis
What stain is used to observe mitosis ?
Toluidene blue stain
What is mitosis important for ?
Growth
Repair
Reproduction
What two stages can the cell cycle be split into?
Interphase and metaphase
What are the sub sections of interphase called?
Growth 1
Synthesis
Growth 2
How much of the cell cycle is interphase?
90%
How long is the average cell cycle ?
24 hrs
What occurs during G1?
Cell prepares for DNA replication
Cell grows
Protein is synthesised
What occurs during synthesis phase?
DNA is replicated
What occurs during G2?
Organelles replicate
Cell grows (increased volume)
Protein synthesis
What are te stages of mitosis called?
Prophase
Metaphase
Anaphase
Telophase
What occurs during prophase?
Nucleolus and nuclear membrane break down
Chromosomes condense (are visible)
Spindle fibres form from centrioles at poles of cell
Spindle fibres attach to centromeres
What occurs during metaphase ?
Spindle fibres align chromosomes at equator of cell
What occurs during anaphase?
Centromeres divide
Spindle fibres contract to pull chromatids to opposite poles of cell
Mitochondria around spindle fibres provide energy
What occurs during telophase?
Spindle fibres disintegrate
Nucleolus and nuclear membrane form
Chromosomes elongate
What occurs during cytokinesis?
Cytoplasm divides in two
Two genetically identical daughter cells form
How does cytokinesis occur?
Cell membrane is pulled inwards
Pinches of cytoplasm
What is binary fission?
Method of reproduction in prokaryotic cells
How does binary fission occur?
Circular DNA and plasmids duplicate
Nucleoids and plasmids move to opposite poles of the cell
Cell membrane extends inwards and pinches of cytoplasm
Cell wall divides
Why aren’t the daughter cells created in binary fission not always genetically identical?
Plasmids are shared unevenly
Why is binary fission simpler than mitosis?
Binary fission doesn’t involve chromosomes, spindle fibres or nuclear envelopes
What does acellular mean?
No cells
How do viruses replicate (2 methods)
Virus attaches to cell host and injects nucleic acids
OR
virus is engulfed and releases nucleic acids into cell
Host cell metabolic processes are used to manufacture proteins, enzymes and nucleic acids to produce more viruses
What is cancer?
Uncontrolled cell division
What is cancer also know as?
Growth disorder of cells
How does cancer arise?
A mutation to genes that regulate the cell cycle
What is the difference between a tumor and cancer?
Cancer is when tumor cells break off and form a secondary tumor (malignant)
How do cells naturally control their numbers?
Programmed cell death
Some lose ability to divide
What factors control the rate of mitosis?
Environmental factors
Genes
Growth factors
How are mutant cells different to normal cells?
They are structurally and functionally different
What is the difference between malignant and benign tumors?
Benign don’t form secondary tumors (not cancer)
Benign are more compact
Benign grow slower
What is metastasis?
The movement of cancer cells from primary to secondary sites/ tumors
What do cancer treatments do?
Disrupt the cell cycle
Give examples of the effects of cancer treatment on cancer cells
Prevent DNA unwinding
Prevent formation of spindle fibres (metaphase)
Prevent cells producing nucleotides
What type of cells does cancer treatment work best against?
Rapidly dividing cells
Cancer and hair cells
Why do cancer patients lose their hair?
Hair cells are rapidly dividing and so are more effected by cancer treatment than other body cells
