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What is the active form of Ras?
Ras GTP
What is the inactive form of Ras?
Ras GDP
How is an intracellular receptor activated?
a non-polar ligand binding to receptor
Where is an intracellular receptor located?
cytosol or nucleus
What does an intracellular receptor do?
causes changes in gene expression
What are the two main types of intercellular receptors?
ligand-gated ion channels and G protein-coupled receptors
How are ligand-gated ion channels activated?
ligand binding to receptor
What is the cellular response of a ligand-gated ion channel?
passive transport of ions
How is a G protein-coupled receptor activated?
a polar ligand binding to the receptor
Where is a G-protein coupled receptor located?
cell surface
What does a G-protein coupled receptor do?
completes signal transduction
What is signal transduction?
G protein receptor exchanges GDP for GTP, binds to and activates adenylyl cyclase enzyme which converts ATP to cAMP which binds to and activates protein Kinase A which phosphorylates target proteins
What is a telomere?
a repetitive DNA sequence found at either end of linear chromones, typically found in germ cells or stem cells and sometimes cancer cells
What does helicase do?
separates DNA strands
What does DNA ligase do?
forms a phosphodiester bond to join two DNA fragments
What does telomerase do?
restores tips of chromosomes that were shortened during replication
What does primase do?
creates an RNA primer
What impact does a phosphatase have on a signal transduction protein?
it removes a phosphate causing the protein to change shape
Where in this pathway would a phosphatase act to terminate the actions of a kinase?
On the protein target
What is Kinase?
an enzyme that adds phosphate groups to proteins
What is Phosphatase?
an enzyme that removes phosphate groups from proteins
What are some amplification steps in a Receptor kinase pathway?
activated receptor can activate multiple G proteins, Adenylyl Cyclase can produce multiple cAMP molecules, and Protein Kinase A can phosphorylate and activate multiple target proteins
What type of receptor does a polar ligand interact with?
cell surface receptors
What type of receptor does a non-polar ligand interact with?
intracellular receptors
What is a chromosome?
a structure of DNA and proteins in cells; visible chromosomes are a highly condensed form of DNA wrapped around proteins and observed during M phase of the cell cycle
What is a histone?
proteins around which DNA is wrapped
What is chromatin?
a more loosely packaged form of DNA and proteins found in interphase and G0 cells
What is a homologous chromosome?
a chromosome that contains the same genes in the same order as another chromosome, with overall 95% sequence similarity
What is a sister chromatid?
One of two identical copies of a DNA sequence, formed from DNA replication, that remain attached at the centromere by cohesin proteins until anaphase of mitosis
The interphase stage includes what phases?
G1, S, and G2
The M phase stage includes what phases?
prophase, metaphase, anaphase, telophase, and cytokinesis
What are the key events or features of the G1 phase?
Regulatory proteins are made; growth and preparation for DNA replication; DNA amount does not change
What are the key events or features of the S phase?
DNA replication occurs and amount of DNA in the cell increases
What are the key events or features of the G2 phase?
cell size and protein content increase; DNA amount is doubled but chromosome number is the same
What are the key events or features of the prophase?
This is the first phase of mitosis. The nucleus condenses, the centrioles move to opposite ends of the cell, and the spindle fibers form a bridge to connect the ends of the cell.
What are the key events or features of the metaphase?
this is the second phase of mitosis. During this phase, the chromosomes all line up down the middle of the cell. Additionally, the nuclear membrane has now disappeared completely.
What are the key events or features of the anaphase?
this is the third phase of mitosis. During this phase, the chromosomes pull apart from each other and move to opposite sides of the cell. This process is caused from the split of the centromere of each chromosome. These chromosomes have been pulled by spindle fibers, which has subsequently caused the cell to stretch out.
What are the key events or features of the telophase?
this is the last phase of mitosis. During this phase, new nuclear membranes form. A new nuclear envelope has also formed and the spindle fibers have disappeared. Additionally, there are two new nuclei.
What are the key events or features of cytokinesis?
this is the final phase of the cell cycle. This phase results in the cell splitting into two identical daughter cells. The two daughter cells both contain the same chromosome set and about half the organelles of the parent cell.
What are the key events or features of the G0 phase?
cell is metabolically active but not preparing for cell division
How has the amount of DNA and chromosomes changed after the G1 phase?
no change, 2 DNA and 2 chromosomes
How has the amount of DNA and chromosomes changed after the S phase?
only doubled DNA, 4 DNA and 2 chromosomes
How has the amount of DNA and chromosomes changed after the G2 phase?
no change, 4 DNA and 2 chromosomes
How has the amount of DNA and chromosomes changed after the M phase?
half the DNA, 2 DNA and 2 chromosomes
What is CDK?
cyclin-dependent kinase, a kinase protein that becomes active after binding to a cyclin
What is the function of CDK?
phosphorylates target proteins
When are Cyclin-D proteins active in the cell?
G1, S, and G2
When are Cyclin-E proteins active in the cell?
Late G1, early S
When are Cyclin-A proteins active in the cell?
S, G2
When are Cyclin-B proteins active in the cell?
G2, early M
How are cyclin protein levels increased in a cell?
gene expression (transcription+ translation)
How are cyclin protein levels decreased in a cell?
protein degradation (protein breakdown)
What is cyclin?
a protein that is synthesized and then degraded in concert with events of the cell cycle; binds to a CDK to promote events of the cell cycle
What three molecules does CDK need to bind to carry out its function?
ATP, cyclin, and a target protein.
What is the function of P53?
prevents progression through the cell cycle (tumor suppressor)
How is P53 activated?
by detecting DNA damage
What is the function of Ras?
activates the Ras/MAPK pathway, resulting in the expression of genes for cell division (proto-oncogene)
How is Ras activated?
when mitogens are present
What is APC?
leads to anaphase of M phase and completion of cell division (proto-oncogene)
How is an APC activated?
when all sister chromatids are attached to the mitotic spindle
What kinds of mutations to proto-oncogenes are usually associated with cancer?
mutations that activate them because they promote progress through the cell cycle under circumstances when they should not be progressing
What kinds of mutations to tumor suppressors are usually associated with cancer and why?
mutations that inactivate them because they no longer inhibit progress through the cell cycle under circumstances when they should stop it
What are the two main rules for initiating DNA replication?
1) DNA polymerase can only add incoming nucleotides to the 3′ end of an existing strand.
2) DNA polymerase cannot initiate synthesis using a single-stranded DNA template, it can only add a nucleotide to the 3’ end of another nucleotide that is part of a double-stranded polynucleotide molecule
During DNA replication, why is a primer required?
DNA polymerase requires a double-stranded sequence with a free 3' end
What is the role of the RNA polymerase
transcribes the cyclin gene
What is the function of DNA polymerase?
adds nucleotides to the DNA daughter strand one by one on the 3’ end
Newly synthesized DNA fragments have an RNA primer at which end?
the 5’ end
What is directly deactivated when bound GTP is hydrolyzed to GDP + Pi?
G-protein
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