Microbiology: Transcription and Translation

RNA Polymerase

A complex enzyme that carries out transcription by making RNA copies (called transcripts) of a DNA template strand.

Svedberg Unit

A measure of rate of sedimentation in centrifugation rather than size.

Core polymerase and sigma factor

In bacteria, the RNA polymerase is composed of these two subunits.

True

In bacteria, transcription and translation are coupled (True/False).

Nuclear Membrane

In eukaryotes, transcription occurs within this area of a cell.

Cytoplasm

In eukaryotes, translation occurs in this area of a cell.

Initiation

In polypeptide synthesis, this stage brings the two ribosomal subunits together, placing the first amino acid in position.

Termination

In polypeptide synthesis, this stage releases the completed protein when it encounters a stop codon.

Elongation

In polypeptide synthesis, this stage sequentially adds amino acids as directed by mRNA transcript.

20

Number of amino acids.

61

Number of non-terminating codons.

64

Number of possible codons.

3

Number of stop codons.

70S Ribosome

Prokaryotic ribosome used to make proteins.

Initiation

RNA polymerase, with the help of a sigma factor, forms a complex with DNA, resulting in unwinding of DNA by one helical turn. Transcription begins and the first rNTP (usually a purine) is attached.

Genetic Code

The information encoded within the genetic material that can be translated into a protein.

Lon and ClpP

These are examples of ATP-dependent proteases.

Proteasome

These are protein-degrading machines found in eukaryotes and archaea.

Initiation, Elongation, and Termination

These are the stages of polypeptide synthesis.

DnaK

These protein chaperones do not form rings but instead clamp down on a polypeptide to assist in folding.

GroEL and GroES

These protein chaperones form a stacked ring with a hollow center and proteins that fit inside the open hole.

Chloramphenicol and Erythromycin

These two antibiotics bind to the 23S rRNA of the 50S ribosomal subunit.

Streptomycin

This antibiotic inhibits the 70S ribosome formation found in translation.

SecA-dependent general secretion pathway

A common pathway that delivers periplasmic proteins from the ribosomes to the periplasm.

Shine-Dalgarno Sequence

A ribosomal binding site (5'-AGGAGGU-3') in prokaryotic mRNA, located upstream of the start codon.

Codon

A sequence of three nucleotides that together form a unit of genetic code (amino acids) in a DNA or RNA molecule.

3' (Acceptor) End

A subunit of tRNA that binds to the amino acid.

True

Before RNA polymerase has even finished making an mRNA molecule, ribosomes will bind to the 5' end of the mRNA and begin translating protein (True/False).

Consensus Sequence

Comprises the most commonly encountered nucleotides found at a specific location in DNA or RNA. In E. coli, sigma-70 occurs at -10 and -35 positions.

Transcription

The synthesis of a strand of mRNA from a DNA template by RNA polymerase.

Anticodon

A three-nucleotide base sequence on tRNA that hydrogen bonds in an anti-parallel fashion with the mRNA codon specifying an amino acid.

Signal Recognition Particle

A universally conserved ribonucleoprotein that directs the traffic of proteins within the cell and allows them to be secreted.

Termination

All bacterial genes use one of two known termination signals - Rho-dependent or Rho-independent - to accomplish this.

ATP-Dependent Proteases

Enzyme that performs proteolysis; protein catabolism by hydrolysis of peptide bonds.

False

Eurkaryotic microbes have the same transcription/translation method (True/False).

Gram-Negative

In this type of bacteria, proteins are exported completely out of the cells (digestive enzymes and toxins).

Translation

Once a gene has been copied into mRNA, this step decodes the RNA message to synthesize proteins.

Rho-Independent

One of two known transcription termination signals that relies on a NusA protein and contact between NusA and polymerase causes termination.

Rho-Dependent

One of two known transcription termination signals that relies on a protein called Rho and the contact between Rho and RNA polymerase causes termination.

N-terminal Signal Sequence

Proteins meant for the cell membrane are tagged with this hydrophobic sequence of 15-30 amino acids.

50S

The larger subunit of the 70S ribosome of prokaryotes. It is the site of inhibition for antibiotics such as macrolides, chloramphenicol, clindamycin, and the pleuromutilins. It includes the 5S ribosomal RNA and 23S ribosomal RNA.

Elongation

The sequential addition of ribonucleotides from nucleoside triphosphates while RNA polymerase continues to move along the template. Positive supercoils before the polymerase are removed by DNA topoisomerases.

30S

The smaller subunit of the 70S ribosome found in prokaryotes. It is a complex of the 16S ribosomal RNA and 22 proteins. It complexes with the larger 50S subunit to form the 70S prokaryotic ribosome in the cell.

tRNA molecule

These are the decoder molecules that convert the language of RNA into that of proteins and these subunits are shaped like a clover leaf.

Ribosome

These are the subunits of a cell that read the language of mRNA and convert, or translate, it into protein via the genetic code.

Initiation, Elongation, and Termination

These are the three steps of transcription.

UAA, UAG, and UGA

These are the three stop codons.

Anticodon and 3' (Acceptor) End

These are the two functional region of a tRNA molecule.

30S and 50S

These are the two subunits of 70S ribosomes.

Streptomycin, Tetracycline, Chloramphenicol, and Erythromycin

These four antibiotics affect translation.

16S rRNA

These genes are used in reconstruction phylogenies and relation to evolutionary distance.

Tetracycline

This antibiotic inhibits translation by binding to the 30S subunit during translation.

Actinomycin D

This is one of two antibiotics that affect transcription without harming the host. This antibiotic non-selectively binds to DNA and inhibits transcription of elongation.

Rifamycin B

This is one of two antibiotics that affect transcription without harming the host. This antibiotic selectively binds to the bacterial RNA polymerase and inhibits transcription initiation.

5'-AGGAGGU-3'

This is the consensus sequence found 4-8 bases upstream of the start codon in E. coli.

Initiation

This is the first phase of transcription when RNA polymerase holoenzyme binds to the promoter site.

Elongation

This is the second phase of transcription when the RNA chain is extended.

Promoter

This is the specific region of a gene where RNA polymerase can bind and begin transcription.

AUG

This is the start codon.

Termination

This is the third phase of transcription when RNA polynerase detaches from the DNA after the transcript is made.

Down mutation

This mutation in a promoter causes a decrease in transcription.

Up Mutation

This mutation in a promoter causes an increase in transcription.

30S

This ribosomal subunit binds to mRNA and reads the code present in mRNA.

50S

This ribosomal subunit recieves the amino acids brought in by tRNA and links them together thus forming a protein.

Sigma Factor

This subunit of RNA polymerase is required for initiation phase and helps the core enzyme detect the promoter.

Core polymerase

This subunit of RNA polymerase is required for the elongation phase.

Type I

This type of secretion enzyme moves proteins to the extracellular environment.

Protein Factor and GTP

To undergo polypeptide synthesis, each phase requires these.

Upstream Region

Transcription initiation in prokaryotes occurs when the sigma factor binds the promoter orientating RNA-polymerase in this area of DNA, typically -35 and -10 nucleotides from the start site.