Chapter 9: The cell cycle Flashcards
3 key roles of cell division
Growth, repair, asexual reproduction (not in humans though, only unicellular organisms)
Example of cell division growth
Sand dollar fertilized egg divides to form 2 cells for the embryo (then a lot more to make a sand dollar)
Example of cell division repair
Bone marrow cells divide to give rise to new blood cells (CHECK?)
Example of cell division reproduction
1 amoeba divides to become 2 amoebas (there isn’t that much to this one)
How many chromosomes are in a human somatic cell?
46
What is a somatic cell?
A body cell of an organism that isn’t a reproductive cell, so it has 2n chromosomes
How many chromosomes are in a prokaryotic cell?
1 circular chromosome
What is a gamete?
A reproductive cell that has n chromosomes (like sperm or eggs)
How many chromosomes in a human gamete?
23
Similarities between replicated and unreplicated chromosome (assuming that the replicated one was a later version of the unreplicated one)
They are both 1 chromosome
They both have genes and DNA (which is the same - same places, same information)
They both have chromatids
Differences between replicated and unreplicated chromosome (assuming the replicated came from the unreplicated one)
Sister chromatids instead of just the 1
Unreplicated has kinetochore at center, replicated has centromere
Unreplicated will not split, replicated will
Difference between chromatin and chromosomes
Chromatin - Complex of DNA and proteins that build chromosomes, loose and wiggly
Chromosomes - tight chromatin
Summary of how DNA divides (and I mean REALLY gloss over the stuff)
- Unduplicated chromosome
- Duplicates and condenses
- so now it’s 2 sister chromatids with a copy of the DNA
- and when they get separated
- you end up with 2 identical daughter cells.
If a chicken cell has 78 chromosomes, how many chromosomes will be in the gametes and how many will be in each somatic cell of the chicken’s offspring?
39 in gamete, 78 in offspring somatic cells
Cytokinesis
Division of the cytoplasm via cleavage furrow or cell plate
Mitosis (not pmat)
Division of nuclear material and DNA
What happens in G1?
Cell grows, cell structures (like lysosomes or Golgi) are duplicated, mitochondria and chloroplasts divide by binary fission
What happens in S phase?
DNA is duplicated, each chromosome has 2 copies (sister chromatids)
What happens in G2 phase?
DNA replication checked for integrity, mistakes are fixed, nuclear envelope encloses nucleus, 2 centrosomes (that contain centrioles in animal cells)
What happens in M phase?
The cell divides (prophase, prometaphase, metaphase, anaphase, telophase) and also cytokinesis is like right after this
What phase of the cell cycle aligns with replication? Checkpoint here
Between G1 and S
What phase of the cell cycle or mitosis could be considered alignment? (not necessarily the checkpoint)
Metaphase
What phase of the cell cycle or mitosis could be considered separation?
Anaphase
Where are the 3 checkpoints?
Between G1 and S (do you have the stuff do duplicate the dna?), between G2 and M (are there any mistakes before dividing?), between Meta and Ana phase (is everything going to separate properly?)
Cytokinesis process in animal cell
Cleavage furrow forms to pinch the cell in two
Cytokinesis process in plant cell
Vesicles move to the middle to form a cell plate that expands to form 2 cell walls
Summarize binary fission
Bacteria replicates circular chromosome, copy moves to other end of cell, cell membrane pinched inward and off, 2 daughter cells
Prokaryote and Eukaryote cell division similarities
Use most of old cell wall, replicate chromosomes, divide chromosome and cytoplasm, have parent and daughter cell (yeah not much)
Prokaryote and eukaryote cell division differences
Mitosis vs nah
Mitotic spindle vs nah
number of chromosomes
cleavage furrow and cell plate vs tubulin like protein pinching off cell membrane
Binary fission vs nah
Why does skin divide a lot while nerves do not?
If it needs constant replacement, growth, or repair, it will divide often. A fully developed nerve doesn’t need that but skin does
What is a cell cycle control system?
A set of cyclically operating molecules in the cell that triggers and coordinates key events in the cell
What happens in G0 phase?
Nondividing state - cell leaves cell cycle to do its job.
What happens in prophase?
Bye bye nucleus, chromosomes form (get tight)
What happens in metaphase?
The chromosomes line up in the center with the help of the mitotic spindle
What happens in anaphase?
The chromosomes split apart (still with the help of the mitotic spindle) so now there are 92 chromosomes in there
What happens in telophase?
There are 2 nuclei now and they go to opposite ends of the cell
T or F molecular signals in the cytoplasm regulate the cell cycle
True
If your cell didn’t have the left hand chromosome and ignored the checkpoint, what could happen?
It divides and suddenly you have a ton of cells that don’t have the left hand chromosome so now you don’t have a left hand
What is a cyclin?
A regulatory protein that changes in concentration and binds to CDK to do things and can be earned by doing tasks
What is CDK
A simp
Cyclin-dependent kinase that has a fixed concentration and binds to cyclin to phosphorylate reactions and do things
How do cyclins and cdks work together?
As cyclin is earned by doing tasks, it binds to CDK to form cyclin-cdk complexes. With enough of those complexes, they will be able to phosphorylate reactions around the cell like starting s phase, condensing chromosomes, and more. Without enough cyclin, those things won’t happen, and without doing tasks to perfection, there won’t be enough cyclin.
What does MPF trigger?
MPF (maturation/mitosis/M phase promoting factor) triggers M phase by binding to CDK and handing phosphate tags (hot potatoes if you will) to the targets, causing them to break down. 1 specific activity = nuclear membrane breakdown, another is targeting chromosome condensation
What would a cyclin graph FOR END OF G2 START OF M PHASE CYCLIN THERE ARE MANY KINDS look like?
………………../l
……………../…\
…………../……\
………../……….\
____/…………….\
Ignore periods
Stays low until built up to prepare for M phase, when there’s enough M phase happens and levels plummet
T or F Cdk concentration changes
F
T or F More growth factor (prolly hormone) = more division
True - more cdk and cyclin activity, more division, yes
What is density dependent inhibition
Crowded cells stop dividing
What is anchorage dependence?
Cells must be attached to something in order to divide (tissue, other cells, culture flask)
T or F Cancer follows density dependent inhibition and anchorage dependence
False
How does cancer keep growing?
- Ignore cell cycle checkpoints
- Produce own growth factor
- Ignore density dependent and anchorage dependence
- Stop at random points or just don’t
- Divide far more times than a normal cell should in its lifetime
Benign vs Malignant tumor
Benign - Doesn’t move from og site, not likely to kill you
Malignant - Does metastasis (moves from original site (distant locations)) and hogs space in organs and squeezes you from the inside out (which is what kills you)
