BS 161 Exam 3 Completed

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 + P_i?

G-protein