Homework Questions Exam 3 Flashcards
What is the initial target of the RNA polymerase?
The promoter
RNA polymerase is guided by the
Template strand of the DNA
RNA that has hydrogen bonded to itself forms a
Stem loop
How would you increase the concentration of a particular polypeptide in a cell?
Increase the level of transcription
During elongation, what direction is RNA synthesized?
5’ to 3’
In the process of transcription, promoters are specific sequences of ______________ that are recognized by ___________________.
DNA
Sigma factors.
The function of RNA polymerase is to
Catalyze the formation of phosphodiester bonds between ribonucleotides.
Polycistronic transcription units are common in
Both Archaea and bacteria
Many pharmaceutical drugs specifically inhibit transcription in bacteria but not in archaea or eukarya. Why would drugs that inhibit transcription only affect bacteria and not archaea even though they are both prokaryotes?
Archaea and eukarya have very similar RNA polymerases that are different than bacterial RNA polymerases
The template for RNA polymerase is _______________ and the new RNA molecule is _______________ to the template.
DNA
Antiparallel and complimentary
termination of RNA synthesis is ultimately determined by
Specific nucleotide sequences on the template strand
What is the definition of polycistronic mRNA?
A single piece of mRNA that contains the transcript of multiple genes.
True or false: Inverted repeats are common features of transcription termination sequences in all 3 domains of life.
True
What results in the process of bacterial translation?
A polypeptide
How is bacterial translation different from eukaryotic translation?
Bacteria can begin translation before transcription has terminated
Ribosomes move along the mRNA in which direction?
5’ to 3’
How do prokaryotes determine where to begin translation so the correct protein is synthesized?
The rRNA recognizes the correct start codon with the aid of upstream Shine-Dalgarno sequence.
The process of synthesizing proteins involves translation one “language,” nucleic acid sequences, into another “language” amino acid sequence. the cellular component that does the actual translating from codons to amino acids is the ________________.
tRNA
Transfer RNA molecules function
to transfer the correct amino acids to the ribosome during translation
The codon on the _______________ matches with the anticodon on the _____________ to direct the addition of the correct amino acid to the growing polypeptide chain.
MRNA
TRNA
A triplet of bases on an mRNA molecule is known as a(n)
Codon
True or false: Aminoacyl-tRNA synthetase catalyzes the action between the appropriate amino acids and ATP to form an activated amino acid: AA + ATP <—-> aminoacyl-AMP + P-P
True
What are the products of semiconservative replication for a double stranded DNA molecule?
Two double stranded DNA molecules, each consisting of one parental stand and one daughter strand.
Why is DNA replication essential for a cell?
An organism must copy its DNA to pass genetic information to its offspring
What is the function of the parental DNA in replication?
It serves as the template for DNA replication.
Supercoiling is important for DNA structure because
It condenses the DNA so that it can fit inside the cell.
The two strands of the DNA double helix are held together by
Hydrogen bonds between nucleotide bases
In complementary base pairing of DNA, adenine pairs with ____ (or _______ in RNA) and cytosine always pairs with __________.
Thymine
Uracil
Guanine
Each adenine-thymine base pair has ________ hydrogen bonds while each cytosine-guanine base pair has ___________ hydrogen bonds.
2
3
DNA-binding proteins interact predominantly within which portion of a double stranded DNA helix?
Major groove
Given the following DNA sequence (5’ to 3’) what would be the DNA sequence on the complimentary strand (3’ to 5’) of the double stranded helix molecule?
DNA sequence: AGTCCGA
TCAGGCT
What genetic element is transcribed into a single mRNA?
the structural genes
Which operons are always transcribed unless deactivated?
Repressible operons
Which operons are never transcribed unless activated?
Inducible operons
Where on the DNA strand does a repressor bind?
the operator
When the cell is not in the presence of tryptophan,
RNA polymerase can transcribe mRNA
When is the repressor protein transcribed?
It is always transcribed
Why is the tryptophan operon turned off in the presence of tryptophan?
tryptophan binds to and activates the repressor proteins; the repressor proteins, in turn, bind to the operator, preventing transcription.
What is the overall function of the trp operon?
to ensure that the cell has a supply of tryptophan at all times.
How do the repressor proteins block the transcriptions of the structural genes?
It binds to the operator when activated.
What is the inducer molecule in the lac operon?
Allolactose
With which genetic region do the repressor proteins interact?
The operator region
When the cell in not in the presence of lactose,
The repressor proteins bind to the operator.
What is the basic function of the lac operon?
To code for enzymes involved in catabolizing lactose
To what genetic element does the RNA polymerase bind?
The promoter
A recombinant cell
Is a cell that receive DNA from an outside source and incorporates it into its own
What is the hallmark of all horizontal gene transfers
Transfer of. DNA between organisms of the same generation
What are the 3 types of horizontal gene transfer in bacteria?
Transduction, conjugation and transformation
What is the function of the conjugation pilus?
It pulls the F+ and F- cells together
What is required by an F- cell to become an F+ cell?
F plasmid
What is the key difference between donor cells and recipient cells?
An F plasmid
What cellular macromolecule is the fertility factor comprised of?
Nucleic acid
At which point does the recipient cell become an F+ cell?
During the formation of the complimentary strand of the F factor
How does an F+ cell different from an Hfr cell?
Hfr strains have the F plasmid integrated into the chromosome.
Why does conjugation between an Hfr strain and an F- strain not result in 2 Hfr strains?
Conjugation is typically disrupted before the fertility factor can be transferred.
What is a characteristic of a F+ cell?
Ability to synthesize sex pili, presence of fertility factor and ability to mate with an F- cell.
What benefits does the F- strain receive from mating with an Hfr strain?
It acquires new, potentially beneficial genes from the Hfr strain
What base is not found in DNA?
Uracil
DNA replication always proceeds in only one direction because the _________ of the incoming nucleotide is attached to the free _________ of the growing DNA strand .
5’-phosphate
3’-hydroxyl group
What is formed on the lagging strand during DNA synthesis?
Okazaki fragments
the function of the DNA polymerase is to catalyze
The addition of Deoxynucleotides
During DNA replication, Okazaki fragments are linked together by ___________, an enzyme that creates phosphodiester bonds between nicked fragments of DNA.
DNA ligase
In DNA replication, there are leading and lagging strands because
DNA replication is semiconservative and each strand is copied simultaneously in opposite directions.
Which statement illustrates why DNA polymerase cannot initiate a new DNA strand?
DNA polymerase requires a preexisting 3’ hydroxyl group in order to add nucleotides
true or false: DNA replication is bidirectional in prokaryotes with circular chromosomes?
true
