Bio 141 Exam 2 Flashcards
study for exam 2 - biology
What did the transformation factor do in Griffith’s experiment?
Killed S strain transformed the live R strain into a live S strain
What was Fred Griffith’s experiment? (What was done/results)
Live R strain - benign
Live S strain - virulent
Killed S strain - benign
Live R & killed S strain - virulent
Which DNA experiment dealt with protein, DNA and RNA?
Avery Macleod and McCarty
What were the cells labeled with in the cell cycle experiment?
A pulse of radioactive thymidine followed by a chase of nonradioactive thymidine
Where does thymidine show up first? (Which compartment and phase)
Since it is a DNA precursor, nucleus and S phase.
The first labeled mitotic cells were observed about 4-5 hours after the end of labeling period, what is this 4-5 hour phase?
G2 phase. Takes 4 hour for cells to begin mitosis from S phase.
Mitotic cells continue to appear over the next 6-8 hours, what is this phase?
S phase
What is MPF?
Mitosis promoting factor, made up of 2 polypeptide subunits.
Is MPF different in different species of eukaryotes?
No, MPF induces mitosis in all eukaryotes in the same way
How can the protein kinase be a trigger for initiating M-Phase?
The protein kinase subunit, or CDK, can only be active when bound to the cyclin subunit. This cyclin subunit has fluctuating concentrations which build during interphase and peak during M phase, initiating it.
What activates MPF and when does this activation occur?
MPF’s Cdk subunit becomes phosphorylated after it binds to cyclin, but later in the G2 phase, enzymes cause one phosphate group on Cdk to drop off and this dephosphorylation reaction changes MPF’s shape in a way that activates it.
What causes the MPF concentration to decline sharply during M-Phase?
negative feedback, the onset of mitosis triggers an enzyme complex that degrades MPF
Where in the cell cycle are the checkpoints found?
end of G1, G2 and Metaphase
What does G1 checkpoint check for? If conditions not met?
size, availability of nutrients, damaged DNA, social signals
if not met, p53, a protein can activate genes that stop cycle to repair or induce apoptosis
What does G2 checkpoint check for? If conditions not met?
damaged DNA and that DNA is replicated correctly. if not met dephosphorylation and activation of MPF are blocked and cells remain in G2
What does Metaphase checkpoint check for? If conditions not met?
makes sure the spindle apparatus is correctly attached to the kinetochores on the centromeres of chromosomes, if they are not, M phase arrests at metaphase
Most cells in multicellular organisms do not divide in response to the arrival of nutrients (as do unicellular organisms) because ______________ ?
It is not necessary for them to divide
In multicellular organisms individual cells are generally allowed to divide only when ______________ .
in response to signals from other cells. This prevents cancerous growth and will allow for controlled regulated growth.
Cancer is said to involve the loss of cell-cycle control. What does this mean?
This means that the checkpoints are not working properly and cells are growing uncontrollably despite lack of social signals.
What are growth factors and what role do they play in the control, or loss of control of the cell cycle?
Growth factors are polypeptides or small proteins that stimulate cell division and social control of cell cycle is based upon them.
What is the relationship of cancer to the G1 checkpoint?
Cancer is related to the G1 checkpoint because this is where tumor suppressors are supposed to stop excessive growth.
In mitosis how are chromosomes arranged during metaphase, and what takes place immediately after metaphase?
Spindle fibers line chromosomes on the metaphase plate in the middle of the cell. Immediately after metaphase, the sister chromatids are split by the tension from the spindle fibers to form separate chromosomes (anaphase).
What is the equivalent process of anaphase in meoisis?
anaphase II in meiosis II
What is different about the “ploidy” of the cells undergoing anaphase in mitosis and anaphase II in meiosis?
diploid in mitosis and haploid in meiosis. This is because in mitosis, all replicated chromosomes in the cell line up in the middle and sister chromatids split apart. In anaphase II in meiosis, homologous chromosomes have already separated in Meiosis I and therefore ploidy is now haploid.
Does crossing over occur during mitosis?
No, because mitosis results in 2 identical cells and crossing over involves the exchange of genetic material and the two cells would not have identical genetic material.
When does crossing over occur?
Meiosis I during late prophase I
How can the protein kinase be a trigger for initiating M-Phase?
The protein kinase subunit, or CDK, can only be active when bound to the cyclin subunit. This cyclin subunit has fluctuating concentrations which build during interphase and peak during M phase, initiating it.
What activates MPF and when does this activation occur?
MPF’s Cdk subunit becomes phosphorylated after it binds to cyclin, ), but later in the G2 phase, enzymes cause one phosphate group on Cdk to drop off and this dephosphorylation reaction changes MPF’s shape in a way that activates it.
What causes the MPF concentration to decline sharply during M-Phase?
negative feedback, the onset of mitosis triggers an enzyme complex that degrades MPF
Where in the cell cycle are the checkpoints found?
end of G1, G2 and Metaphase
What does G1 checkpoint check for? If conditions not met?
size, availability of nutrients, damaged DNA, social signals
if not met, p53, a protein can activate genes that stop cycle to repair or induce apoptosis
What does G2 checkpoint check for? If conditions not met?
damaged DNA and that DNA is replicated correctly. if not met dephosphorylation and activation of MPF are blocked and cells remain in G2
What does Metaphase checkpoint check for? If conditions not met?
makes sure the spindle apparatus is correctly attached to the kinetochores on the centromeres of chromosomes, if they are not, M phase arrests at metaphase
Most cells in multicellular organisms do not divide in response to the arrival of nutrients (as do unicellular organisms) because ______________ ?
It is not necessary for them to divide
In multicellular organisms individual cells are generally allowed to divide only when ______________ .
in response to signals from other cells. This prevents cancerous growth and will allow for controlled regulated growth.
Cancer is said to involve the loss of cell-cycle control. What does this mean?
This means that the checkpoints are not working properly and cells are growing uncontrollably despite lack of social signals.
What are growth factors and what role do they play in the control, or loss of control of the cell cycle?
Growth factors are polypeptides or small proteins that stimulate cell division and social control of cell cycle is based upon them.
What is the relationship of cancer to the G1 checkpoint?
Cancer is related to the G1 checkpoint because this is where tumor suppressors are supposed to stop excessive growth.
In mitosis how are chromosomes arranged during metaphase, and what takes place immediately after metaphase?
Spindle fibers line chromosomes on the metaphase plate in the middle of the cell. Immediately after metaphase, the sister chromatids are split by the tension from the spindle fibers to form separate chromosomes (anaphase).
What is the equivalent process of anaphase in mitosis in meoisis?
anaphase II in meiosis II
What is different about the “ploidy” of the cells undergoing anaphase in mitosis and anaphase II in meiosis?
diploid in mitosis and haploid in meiosis. This is because in mitosis, all replicated chromosomes in the cell line up in the middle and sister chromatids split apart. In anaphase II in meiosis, homologous chromosomes have already separated in Meiosis I and therefore ploidy is now haploid.
Does crossing over occur during mitosis?
No, because mitosis results in 2 identical cells and crossing over involves the exchange of genetic material and the two cells would not have identical genetic material.
When does crossing over occur?
Meiosis I during late prophase I
What evidence eliminated dispersive model of DNA synthesis?
In generation 2 there was one intermediate density band and one low density band whereas dispersive model says it should have been a hybrid band
What evidence eliminated conservative model of DNA synthesis?
In generation 1 there was a hybrid band instead of 1/2 low density and 1/2 high density
What does conservative replication look like after 2 generations?
1/4 high density and 3/4 low density
What does semi conservative replication look like after 2 generations?
1/2 low density and 1/2 intermediate density
What are promoters?
Sections of DNA where transcription begins, they are binding sites
40-50 base pairs long
What are the two boxes in promoter sequences?
-10 & -35 boxes which are 10 and 35 base pairs upstream from the gene
What is significance of -10 & -35 box?
In bacteria, sigma binds to these boxes initiating transcription
What is the role of the sigma factor?
Act as a regulatory DNA binding protein, guiding RNA polymerase, and allowing it to attach to the DNA strand
How is cancer related to G1 checkpoint?
This is where tumor suppressors such as p53 are supposed to stop excessive growth
When does crossing over occur?
In meiosis 1 in late prophase 1
. In a human germ cell prepared to undergo meiosis, how many replicated chromosomes are present? and how many DNA molecules?
46 chromosomes and 92 individual DNA molecules
After meiosis I is complete, how many replicated chromosomes are present in the daughter cells?
there are 23 replicated chromosomes in each daughter cell, there are 46 DNA molecules (because there are 2 sister chromatids in each cell)
After meiosis II is complete, how many chromosomes are present in the daughter cells? How many DNA molecules?
After Meiosis II, there are 23 chromosomes per cell (with each chromatid in a different cell), therefore 23 DNA molecules per cell.
At what point during meiosis are haploid daughter cells first produced? and how many?
There are 2 haploid daughter cells are produced at the end of Meiosis I
Are the chromosomes in daughter cells after meiosis I surrounded by a nuclear membrane?
These cells can be surrounded by a nuclear membrane but it is dependent on the species.
