Week 1 Flashcards
Define Cell Division
The process by which cells make more cells.
A mother cell makes 2 daughter cells
What are 4 purposes for cell divison?
- growth
- cell replacement
- healing
- reproduction
What are the 2 ways cell division can occur?
Mitosis and Meiosis
- Mitosis –> somatic / body cells
- Meiosis –> germ / sex cells
“specialized cell division
What is the major challenge for mitotic cell divison?
to make complete and exact copies of DNA in 2 daughter cells
Describe the difference between Prokaryotes and Eukaryotes.
Prokaryotes
- small and circular
- DNA = in cytoplasm
eg. bacteria
Eukaryotes
- genome = large and linear
- DNA = in nucleus
What are the 4 main phases in the eukaryotic cell cycle?
- M phase : Mitosis and Cytokinesis
- G1 phase: Gap 1
- S Phase: DNA Synthesis
- G2 Phase: Gap 2
Describe the G1 phase / Gap 1
=growth, cellular metabolism
=the longest gap = “recovery”
-approx 50% reduction in cytoplasmic volume
Describe S Phase / DNA Synthesis
=chromosome duplication
- cell copies DNA = DNA content doubles
- makes exact copies
Descibe G2 phase / Gap 2
=preparation for mitosis
-ensures DNA relication is completed for another cycle
Describe M Phase
=chromosomal separation
Define Interphase
= the time between successive mitoses
= G1 + S + G2
What is the G0 Phase?
aka stationary phase ./ quiscent state
=state where cells enter when they aren’t actively cycling/dividing
- out of cell cycle from G1
What are the cells called when they leave in the G0 Phase?
they are “quiescent”.
Define Autosomes.
= homologous chromosomes
What is the human karyotype?
23 pairs
- 22 autosomes
- 1 pair of sex chromosomes
What are the 2 sex chromosomes
XX - Female
X,Y - Male
A human cell w/ 23 chromosomes =
a) haploid
b) diploid
a) haploid
What is duplication in S Phase for?
so that each daughter cell recieves a complete set of chromosomes
Define Ploidy.
= the # of complete sets of chromosomes in a cell
-refers to how much info ( aka DNA)
Define Haploid (n)
= a cell w/ 1 complete set of chromosomes
eg. sperm / egg
Define Diploid (2n)
= has 2 complete sets of chomosomes
-1 from mom, 1 from dad
eg. somatic cell = leaf/ skin cell , stem cell in your colon
( anything that isn’t a sperm / egg )
True / False : in S Phase, the amount of DNA in cell and ploidy level doubles.
False
Yes, the amount of DNA in cell doubles
But, the ploidy level doesn’t change in mitotic cell division
-no new info = no ploidy change
(there is still 2n, but they just have doubles)
What are the 6 Stages of Mitosis
+ describe ploidy level
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
2n = 46
Describe Prophase.
- chromosomes condense
- centrosomes radiate microtubles & migrate to opposite poles
Descirbe Prometaphase.
-microtubles of the mitotic spindle attach to chromosomes
What is a kinetochore?
=a series of proteins that link the specialized part of the centromere to the microtubles of the mitotic spindle
Describe Metaphase.
- chromosomes align in the center of cell
- chromosomes attach to the mitotic spindle and line up at the equator
Describe Anaphase.
-sister chromatids separate and travel to opposite poles
=sister chromatids become individual chromosomes when the centromere splits
Describe Telophase
-nuclear envelope re-forms & chromosomes decondense
-plasma membrane constricts between the 2 nuclei
=almost a full separation
Describe Cytokinesis
-final break / split of the membrane
What is the difference between cytokinesis for an animal and for a plant
Animal
-has a contractile ring of acton = a structural protein
Plant
-has a cell plate, looks like building a new wall
What 2 things can control the progression through the cell cycle
- Proteins; appear and disappear in a cyclial fashion
eg. cyclins - several enzymes; become active and inactive in cycles
What are cyclins?
=proteins that appear and disappear cyclically
Explain how Cyclins function.
also define CDK + describe a cyclins halflife
- cyclins bind to and activate cyclin-dependant kinases (CDK)
- **CDK = a protein and an enzyme that adds a phosphate group to another protein
- cyclin-CDK complexes phosphorylate target proteins that promote cell divison
- phosphate to an amino acid
- has a small half life as a protein
True / False: Cyclins are negative regulators
False!
Cyclins are positive regulators as the target proteins promote the cycle
What are the the 3 specialized cyclin-CDK complexes at each phase of the cell cycle?
( + their functions )
G1 cyclin, S cyclin, and M cyclin push the cell through the cycle.
G1 / S cyclin
-CDK complex prepares cell for DNA replication
S cyclin
-CDK helps initiate DNA synthesis
M cyclin
-CDK helps prepare the cell for mitosis
Why do cells have many “cell-cycle checkpoints”?
It is to pause the cycle if there is an error, before progressing to the next stage
What are the 3 major, well-studied checkpoints?
+ where are they
- DNA replication checkpoint : is all DNA replicated?
@ end of G2
=checks for the presence of unreplicated DNA before the cell enters Mitosis - DNA damage checkpoint : is DNA damaged?
@ before entering S phase
=checks for damaged DNA before the cell enters S phase
3.Spindle assembly checkpoint : are all chromosomes attaced to the spindle?
@ before anaphase
=checks for all chromosomes being attached to the spindle before the cell progresses w/ Mitosis
How can cancer develop?
when normal controls on cell division break down
Define oncogene.
= cancer-causing gene
Define proto-oncogene.
= normal genes important for promoting cell division that have potential to become cancerous if mutated.
Define tumor suppressors.
= genes that encode proteins whose normal activities inhibit cell division.
Describe the multi-step process of cancer development.
- requires sequential mutations in several genes
1. normal cell : inactiviation of 1st tumor suppressor gene
2. benign cancer : activation of oncogene
3. malignant cancer : inactivation of 2nd tumor suppressor gene
- metastatic cancer : inactivation of 3rd tumor suppressor gene
+ metatosis @ a new state
