3.7- MITOSIS Flashcards
How can cell division happen? (2)
by either mitosis or meiosis
What does mitosis produce?
two daughter cells that have same number of chromosomes as parent cell + each other
What does meiosis produce?
four daughter cells, each with half the number of chromosomes of parent cell
What is mitosis?
division of cell that results in each of the daughter cells having an exact copy of DNA of parent cell
In what cases do the daughter cells of mitosis not have the exact copy of DNA of the parent cell?
mutation
When does mitosis precede?
period during which cell not dividing
What is the period when a cell is not dividing called?
interphase
What is the period of interphase of?
period of considerable cellular activity that includes a very important event, replication of DNA
Where is the two copies of DNA after replication remain joined at?
centromere
What four stages can mitosis be divided into?
prophase
metaphase
anaphase
telophase + cytokinesis
What firstly happens in prophase?
chromosomes first become visible
How do the chromosomes change in prophase?
become visible, initially as long thin threads, which later shorten + thicken
What do animal cells contain for mitosis?
two cylindrical organelles called centrioles
Where do the centrioles move to during prophase?
move to opposite ends (called poles) of cell
What do the centrioles develop in prophase?
spindle fibres which span cell from pole to pole
What are spindle fibres collectively called?
spindle apparatus
What shows that centrioles are not essential for spindle fibre formation?
as plant cells lack centrioles but do develop spindle apparatus
What happens to the nucleolus + nuclear envelope in prophase?
nucleolus disappears
nuclear envelope beaks down, leaving chromosomes free in cytoplasm of cell
Where are the chromosomes drawn towards in prophase?
towards equator by spindle fibres attached to centromere
What happens to the chromosomes by metaphase?
chromosomes seen to be made up of two chromatids
What is each chromatid? (metaphase)
identical copy of DNA from parent cell
What are the chromatids joined by? (metaphase)
centromere
What is attached to the centromere? (metaphase)
some microtubules from the poles
What happens when some microtubules from the poles are attached to the centromere? (metaphase)
chromosomes pulled along spindle apparatus + arrange themselves across equator of cell
What happens in anaphase?
centromere divides into two + spindle fibres pull individual chromatids making up chromosome apart
Where and how do the chromatids move after the centromere divides into two? (anaphase)
chromatids move rapidly to respective, opposite poles of cells
When the chromatids move to the opposite poles of the cell what are they referred to as? (anaphase)
chromosomes
Where is the energy of the chromatids moving to the opposite poles of the cell come from?
provided by mitochondria
What do the mitochondria do in anaphase?
gather around the spindle fibres
What happens if the cell is treated with chemicals that destroy the spindle? (anaphase)
chromosomes remain at equator, unable to reach the poles
What happens in telophase?
chromosomes reach their respective poles + become longer + thinner, finally disappearing altogether, leaving only widely spread chromatin
What happens to the spindle fibres in telophase?
spindle fibres disintegrate
What happens to the nuclear envelope + nucleolus in telophase?
re-form
What happens after telophase?
cytoplasm divides
What is the process of the cytoplasm dividing called?
cytokinesis
What is the process of cell division in prokaryotic cells called?
binary fission
What is step 1 of binary fission?
circular DNA molecules replicate + both copies attach to cell membrane
What is step 2 of binary fission?
plasmids also replicate
What is step 3 of binary fission?
cell membrane begins to grow between two DNA molecules + begins to pinch inward, dividing cytoplasm into two
What is step 4 of binary fission?
new cell wall forms between two molecules of DNA, dividing original cell into two identical daughter cells, each with single copy of singular DNA + variable number of copies of plasmids
Why can’t viruses undergo cell division?
they’re non-living
How do viruses replicate?
by attaching to their host cell with attachment proteins on their surface
What do viruses do after attaching to the host cell with their attachment proteins in replication?
inject their nucleic acid into host cell
What does the genetic information of the injected viral nucleic acid from the virus provide in replication?
“instructions” for host cell’s metabolic processes to start producing viral components, nucleic acid, enzymes + structural proteins, which are then assembled into new viruses
