Biology Lecture 5: Prokaryotic
Clicker Question: This frozen baby wooly mammoth had a chromosome number of 58. How many
chromatids would be in a cell at the G2 checkpoint?
The number of chromosomes in a cell does not change during mitosis.
Amount of DNA increases during S phase; chromosome # does not!
Interphase Slide: the picture is a immuno fluorescent (light micrograph).
Prophase: chromatin condenses into visible chromosomes.
Chromosomes are present in the nucleus all the time.
Prometaphase and Metaphase:
Prometaphase: microtubules invade fragmented nucleus.
As we move from prophase to metaphase, chromosomes are highly condensed.
Microtubules in metaphase look for kinetochores to attach.
Metaphase: chromosomes align at central plate.
Checkpoint in metaphase makes sure that all of the chromosomes are hooked up to the spindle.
As well to see if the microtubules are connected to kinetochores.
Anaphase: chromatids separate.
Microtubule motor proteins are associated with kinetochores, and pull the chromosome toward
the spindle pole along the microtubules.
Telophase and Cytokinesis:
Telophase and Cytokinesis: We need the cell to get pinched off. Around and in the middle of the
cell the actin filaments work with myosin and contract to cut the cell into two.
Non-kinetochore microtubules push on each other to push the spindle pole apart; while at the
same time the chromotaids are crawling along the other microtubules.
The combined effect of both these movements is for the cell to push its pull apart and get its