MICR 3033 exam 3 (CH 9-12)
12Q6 Why are cancer cells genetically unstable?
They carry serious deletions/translocations that result in chromosomal duplications, deletions, and rearrangements. The incidence of cancer progresses over time, developing during later stages of life.
10.2Q5 How does the actin/myosin ring promote cytokinesis.
the actin/myosin ring assembles perpendicularly to the interloper micro tubular network. the sliding of the actin filaments against the myosin filaments provoking strong a constriction force, separating the cytoplasm.
9Q7 Describe the regulatory switch of the operon that manufactures tryptophan in E. coli.
the repressor TrpR is only active when tryptophan is present which prevents transcription by blocking RNA polymerase when tryptophan is absent the repressor cannot bind to the operate and transcription can occur
12Q5 How do tumors evolve?
tumors develop as cells double create a mass
9Q13 How does epigenetic gene regulation work by DNA methylation?
CpG islands are methylated by DNA methyltransferases which allow for regulation of promoter expression hyper methylation leads to transcriptional silencing, but if the islands are not methylated then the silencing fails and transcription occurs
11.1Q2 What makes stem-cells different from terminally differentiated cells in regard of the genes that they express?
A genetic determinant that plays a critical role in inducing genetic change to stem cell differentiating cells is the positive feedback activation mechanism of a master regulator. Stem cells divide a number of times, and one of the offspring cells with initiate a programmed series of cellular modifications that result in a new cell type. This new cell loses its ability to undergo mitosis.
12Q4 Discuss GENETIC and EPIGENETIC modifications that affect the development ofcancer.
All cells are exposed to multiple forms of DNA modification agents that cause DNA modifications reflected genotypical on its structure genetically, by modifying the DNA sequence or epigenetically, by modifying chromosome condensation and relaxation patterns.
12Q2 Why does the incidence of cancer increase exponentially with age?
As we age, the chances of errors within our DNA code increase making it more likely that these errors will give rise to cancer.
10.2Q2 What are cyclin-dependent kinases (Cdks)?
CDKs associate with cyclins and carry kinase domains that phosphorylate target proteins during various phases in the cell cycle
10.4Q4 Describe the steps of M-CDKs activation.
CDKs need to associate with a cyclin to activate M-cyclins associates with cyclin B and forms a dimer activating kinase and inhibiting kinase phosphorylate the dimer and the CDK is activated
10.5Q5 Why are M-Cdk and S-Cdk regulated by sequential cyclin activation in addition to multiple phosphorylation and dephosphorylating steps?
CDKs undergo multiple steps because they control very important cell functions. Several step mechanisms ensure that checkpoint signals can be properly verified
12Q1 Why are some cancers hereditary? Explain
Cancer will be hereditary when the mutations caused by cancer are present in germ cells.
11.2Q5. In the gut how are the different tissues organized and how are stem-cellsreplenishing terminally differentiated lining cells?
Epithelium lines the lumen which is encased in connective tissue that binds to muscle tissue that is encased in epithelial tissue of the gut. Stem-cells are constantly differentiating cells and sending them to the lumen to become terminally differentiated as these lining cells need constant replacement.
10.1Q1 Define three stages of the cell cycle?
Interphase G0: where cells rest G1: where cells grow and expand S: where DNA is replicated G2: where cells repair damaged DNA and duplicate centrosomes Cell division (M) phase Where cells undergo nuclear and cytoplasmic division
12Q7 Describe an oncogene and its corresponding proto-oncogene?
Oncogenes promote cell proliferation when mutated, gene duplication, chromosomal translocations, and viruses. Proto-oncogenes have mutations that are domination and transform into an oncogene.
11.2Q3 What are connective and epithelial tissues good for?
Primary function of epithelial tissue is secretion and selective absorption of molecules. Connective tissues provide mechanical support connecting otherwise disconnected tissues.
11.2Q2 How are collagen fibers synthesized and assembled in the extracellular space -the connective tissue?
S single collagen polypeptide chain assembles into a tri-fold right handed triple helix with amino and carboxyl terminal extension domains that prevent pro collagen molecules from assembling with fibers. Once procolloagen molecules have been secreted and termini processed by a protease, the resulting collagen molecule assembles spontaneously into fibers.
10.6Q1 Describe how S-CDK controls initiation of DNA replication.
S-CDK-E complex associates with origin of replication complexes (ORCs), recruits DNA polymerase, and fires the replication process.
11.1Q3 How do stem-cells differentiate? What types of genetic mechanisms areinvolved?
Stem cell differentiation is determined by chromosome domain epigenetic regulation. When a stem cell differentiates, the chromatin remodeling complexes act and regulate differentiation by turning specific genes on and off.
10.2Q6 In cytokinesis how are organelles distributed. Which ones are randomly partitioned and which ones are not?
The reformed nuclear envelope contain two identical nuclei that are properly segregated into two cells by cytoplasmic partitions. The mitotic spindle oriented positioning of the cytoplasmic crest. Myosin and actin ring assembles perpendicularly to interpolar microtubule network. None of these organelles are randomly petitioned.
9Q1 What is an operon?
a group of genes that are transncribed into an mRNA molecule
9Q12 How does a positive feedback-loop activation mechanism create memory?
a regulator activates the transcription of its own gene and becomes independent of the primary input signal that activated it originally. Self-activating is often maintained and transferred to descendent cells thus creating a "memorized" differentiated lineage of cells.
9Q6 Describe an inducer? What is a repressor?
both regulate gene expression inducers bind to repressors to deactivate them and allow transcription to occur (positive acting) repressors bind to operator sequences to prevent transcription factors from binding to promoter regions (ngeative acting)
12Q3 How do cancers arise?
cancer cells evolve by the accumulation of mutations. Somatic, germ, and stem cells accrue mutations and transfer them to offspring.
10.2Q3 How is the microtubule network constructed by centrosomes? How many types of networks are assembled and how they differ in their function?
centrosomes cast an extensive microtubule network from each spindle pole (located on opposite sides of the cell) there are 3 types: aster: position spindle poles in the cells kinetochore: connect chromosomes to spindle poles interpolar: connect the 2 spindle poles
10.2Q1 How does a centrosome emerge in the cell?
centrosomes exist in interphase as a single unit and they are copied only once per cell cycle and transferred to offspring
9Q12 Explain how gene expression is controlled by chromatin remodeling complexes (CRCs).
chromatin remodeling uses enzymes to modify histone tail domains and nucleosomes to expose DNA regulatory elements and allow access for transcription factors CRCs anchor themselves to labeled nucleosomes and read histone tail modification patterns to know where to bind
10.2Q2 How do cohesins and codensins work?
cohesins are specialized protein complexes that bundle sister chromatids together then condensins complexes bind to the individual chromosomes and promote condensation of the chromosomes into DNA molecules
11.2Q1 The four main tissues involved in the design of organs and systems in the humanbody are?
epithelial, smooth muscle tissue, nervous, connective
10.2Q4 How does nuclear lamina disintegration coordinate chromosome segregation with microtubule spindle formation.
in metaphase the cell nucleus disintegrates and phosphorylation causes the cell components to disassemble and fuse to the ER in telophase dephosphorylation allows components to regroup around the newly formed nuclei
9Q11 Describe how a regulatory network can guide a developmental process.
it involves modification of cell types so new genes need to be activated by transcription factors which activate each other by a transcription activator network
9Q10 Describe one of the simplest genetic mechanisms, which allow daughter cells to "remember" what kind of cells they are supposed to be.
positive feedback loops can be created by master regulators, which can activate several target genes and other master regulators when a master regulator is able to activate itself it becomes independent of the primary input signal that it previously needed to be activated in stem cells when cells experience changes, positive feedback loops can occur and the changes become permanent
9Q2 What are "regulatory DNA sequences"?
regulatory DNA sequences work like switches to activate or repress a gene they have distal promoters, DNA binding sites, and a proximal promoter - proximal promoters have DNA binding sites and activator/repressor binding sites - transcription factors interact with the binding sites and use molecules called inducers and repressors to enable or disable transcription to occur
9Q14 Describe how RNA interference regulates the expression of genes?
small double stranded RNA molecules degrade a target mRNA molecule or hinder the translation of a mRNA molecule or modify heterochromatin remodeling patterns
11.1Q1 Name and describe the three cell-types that constitute tissues and organs?
somatic cells: cells that reproduce or rise through mitotic cell division and are germ cells germ cells: all the cells involved in reproduction stem cells: stem cells can divide for indefinite periods of time and give rise to terminally differentiated cells.
9Q3 Define structural genes? What are gene regulatory proteins?
structural genes are target genes that code for RNA or proteins related to synthesis rather than cell function gene regulatory proteins control transcription to determine what genes are are expressed
9Q8 Describe the dual nature of the regulatory switch that controls the lactose operon in E. coli.
the cells prefers glucose but in the absence of glucose it can use lactose instead when there is glucose: the repressor LacI binds to the operator motif only when lactose is absent, but when lactose is present and bound to LacI the repressor no longer associates with the operator when there is no glucose but there is lactose: catabolite activator proteins (CAPs) are used as transcription factors to allow transcription to occur when no repressor is present - CAPs bind to cAMP produced by adenylate cyclase which is only active when glucose is low
9Q9 Why is eukaryotic RNA polymerase II phosphorylated?
the tail domains of RNA polymerase are phosphorylated to release it from the promoter and trigger transcription
10.3Q3 What are cell cycle checkpoints?
there are 3 checkpoints (G1/S, G2/M, spindle) for the 4 phases which check for completion and accuracy of the previous step before starting the next one
11.2Q4 Because epithelial tissues coat many organs which perform several functions,what types of cell junctions exist to connect two cells and how they relate to their possiblephysiological function?
they have gap junctions (form channels that allow transport of small intracellular water soluble molecules between neighboring cells), adherens (join actin bundles between epithelial cells), and tight junctions (seal gaps between cells of an epithelial sheet, preventing leakage of materials).
9Q5 What does "positively-acting" mean? What is the outcome of an activator?
this occurs when activator proteins/inducers bind to an operator sequence activators induce transcription by releasing/preventing anything from binding to DNA motifs
9Q4 What does "negatively-acting" mean? What is the outcome of a repressor?
this occurs when repressors prevent transcription factors from binding to the promoter regions repressors prevent transcription from occurring by blocking RNA polymerase
