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Life 205 Chpt. 7
The blueprint of life, from DNA to protein.
56
Microbiology
Undergraduate 2
02/27/2013

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Term
What are the three functional types of RNA molecules?
Definition
1.Messenger RNA (mRNA)
2.Transfer RNA (tRNA)
3.Ribosomal RNA (rRNA)
Term
Most genes encode proteins that are transcribed into what?
Definition
mRNA
Term
The complete set of genetic info in a cell is referred to as what?
Definition
The genome
Term
the process of gene expression involves what two inter-related events?
Definition
Transcription
translation
Term
the process copies the info encoded in DNA into RNA.
Definition
Transcription
Term
This process interprets info carried by RNA to synthesize the encoded protein.
Definition
Translation
Term
A complex of enzymes and other proteins that synthesize DNA. (In an "assembly line")
Definition
Replisomes
Term
This enzyme temporarily breaks the strands of DNA, relieving the tension caused by unwinding the 2 strands of the DNA helix.
Definition
DNA Gyrase (stops the gyrating of the DNA)
Term
This enzyme joins 2 DNA fragments by forming a covalent bond btwn the sugar and phosphate residues of adjacent nucleotides.
Definition
DNA Ligase
Term
This enzyme synthesizes DNA.
Definition
DNA polymerases
Term
What direction does synthesis always occur?
Definition
5' to 3' direction.
Term
In DNA synthesis, nucleotides can only be added to what end of the existing fragment?
Definition
The 3' end.
Term
These enzymes unwind the DNA helix ahead of the replication fork.
Definition
Helicases
Term
Nucleic acid fragment produced during discontinuous synthesis of the lagging strand of DNA.
Definition
Okazaki fragments.
Term
The distinct region of a DNA molecule at which replication is initiated.
Definition
Origin of replication
Term
Enzyme that synthesizes small fragments of RNA to serve as primers for DNA synthesis.
Definition
Primase
Term
A fragment of nucleic acid to which DNA polymerase can add nucleotides. (to an existing fragment only)
Definition
Primer
Term
In transcription, this enzyme synthesizes single-stranded RNA molecules from a DNA template.
Definition
RNA polymerase
Term
The DNA sequence to which RNA polymerase can bind and initiate transcription is called what?
Definition
A promoter
Term
A DNA sequence that stops the process of transcription.
Definition
terminator
Term
What is one major difference btwn RNA polymerase and DNA polymerase?
Definition
RNA polymerase can start transcription without a primer.
Term
The DNA strand that serves as the template for transcription.
Definition
The Minus(-) strand
Term
The complement of the minus strand
Definition
The plus (+) strand
Term
T or F, In prokaryotes, mRNA molecules can carry the info for one or multiple genes?
Definition
True
Term
A transcript that carries one gene.
Definition
monocistronic
Term
a transcript that carries multiple genes
Definition
polycistronic
Term
This is a component of RNA polymerase that recognizes the promoter regions. A cell can have different types that recognize different promoters, allowing the cell to transcribe specialized sets of genes as needed.
Definition
A sigma factor
Term
These identify the regions of the DNA molecule that will be transcribed into RNA. They orient the direction of the RNA polymerase and dictate which strand will be used as the template.
Definition
Promoters
Term
What occurs in the elongation phase?
Definition
RNA polymerase moves along DNA using the (-) strand as a template to synthesize a single-stranded RNA molecule.
Term
Once elongation has proceeded far enough for RNA polymerase to clear the promoter, what can happen?
Definition
A new RNA enzyme can bind, thus a single gene can be transcribed repeatedly very quickly.
Term
What three structures are required for translation?
Definition
mRNA, ribosomes, and tRNA's.
Term
What direction does the ribosome move on the mRNA?
Definition
the 5' to 3' direction.
Term
what are prokaryotic ribosomes composed of?
Definition
a 3OS subunit and a 5OS subunit each made up of a protein and ribosomal RNA.
Term
WHat are the two sites on a ribosome that tRNA can bind? What happens when they are both occupied by a tRNA?
Definition
The P-site and the A-site. When both are filled, an enzyme creates a peptide bond btwn the two amino acids.
Term
the site through which the initiating tRNA is released.
Definition
The E-site
Term
an assembly of multiple ribosomes attached to a single mRNA molecule.
Definition
polyribosome, or polysome
Term
Proteins that assist in the folding of polypeptides.
Definition
Chaperones
Term
How can the cell tell if a polypeptide is destined for transport through the cytoplasmic membrane?
Definition
It will have a signal sequence which is a characteristic series of hydrophobic amino acids that tags them for transport.
Term
What are the four main differences btwn prok and euk gene expression?
Definition
Eukaryotic pre-mRNA must be processed. This involves capping, polyadenylation, and splicing. It must also be transferred out of the nucleus before it can be translated in the cytoplasm. Eukaryotic mRNA is monocystronic.
Term
This transmits information from outside the cell to the inside.
Definition
signal transduction
Term
Some organisms can "sense" the density of cells within their own population. this is called what?
Definition
quorum sensing
Term
THis allows cells to activate genes that are only useful when expressed by a critical mass
Definition
quorum sensing (e.g. biofilms)
Term
an important mechanism that cells use to detect and react to changes in the external environment.
Definition
two-component regulatory system
Term
an alteration in the characteristics of certain surface proteins in a bacterial cell.
Definition
antigenic variation
Term
what allows pathogens to stay one step ahead of the body's defense by altering the molecules our immune systems recognize?
Definition
antigenic variation
Term
What is the routine switching on and off of certain genes?
Definition
phase variation
Term
A set of regulated genes transcribed as a single polycystronic message.
Definition
an operon
Term
separate operons controlled by a single regulatory mechanism constitute a what?
Definition
regulon
Term
The simultaneous regulation of numerous genes is called what?
Definition
global controll
Term
this type of enzymes are synthesized constantly; the genes that encode them are always active. (enzymes of glycolysis)
Definition
constitutive
Term
synthesis of this type of enzyme is turned on when needed. (Beta-galactoisade)
Definition
inducible
Term
these enzymes are produced routinely, but their synthesis can be turned off when they are not required. (generally enzymes used in anabolic pathways)
Definition
repressible
Term
when glucose is available, the lac operon is not expressed because of a phenom called what?
Definition
Carbon catabolite repression (CCR)
Term
The two-phase growth pattern between the use of glucose and other carbon /energy sources.
Definition
diauxic growth
Term
One mechanism of carbon catabolic repression involves an activator called _____ that is bound by an inducer cAMP.
Definition
CAP (catabolite activator protein)
Term
In the eukaryotic cell, this is routinely used to destroy specific RNA transcripts
Definition
RNAi (interference RNA)
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