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Enzymes called ____________ form breaks in the DNA molecules toprevent the formation of knots in the DNA helix during replication.
topoisomerases
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Which of the following adds new nucleotides to a growing DNA chain?
DNA polymerase
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Why does DNA synthesis only proceed in the 5´ to 3´ direction?
Because that is the direction in which the two strands of DNA unzip.
-
The 5´ end of each Okazaki fragment begins with:
a separate RNA primer.
-
Primase is the enzyme responsible for:
making short strands of RNA at the site of replication initiation.
-
In DNA replication, the lagging strand:
is synthesized as a series of Okazaki fragments.
-
Okazaki fragments are joined together by:
RNA ligase.
-
How are the chromosomes of a eukaryote cell replicated?
The linear DNA molecules are replicated from multiple origins of replication bidirectionally.
-
____________, the ends of eukaryotic chromosomes, shorten with every cell replication event.
Telomeres
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Cancer cells differ from noncancerous cells in that:
All of these.
-
Ribose differs from deoxyribose by having:
an extra hydroxyl group.
-
Uracil forms a complementary pair with ____________ in RNA and _____________ in DNA.
adenine; adenine
-
RNA synthesis is also known as:
transcription.
-
The codon is found in the:
mRNA.
-
Which of the following serves as an “adapter” in protein synthesis and bridges the gap between mRNA and proteins?
tRNA
-
During protein synthesis, ribosomes:
attach to the mRNA molecule and travel along its length.
-
How is the 4-letter language of nucleic acids converted into the 20-word language of amino acids?
The 4 nucleic acid bases combine in 3-letter sequences that define different amino acids.
-
The wobble hypothesis states that:
certain tRNA anticodons can pair with more than one codon sequence.
-
A sequence of bases located upstream from a reference point occurs:
towards the 5´ end of the mRNA sequence.
-
Initiation of transcription requires:
a promoter sequence.
-
Why is only one strand of DNA transcribed into mRNA?
Because transcribing both DNA strands would produce different amino acid sequences.
-
Aminoacyl-tRNA synthetases ________ link ________ to their respective tRNA molecules.
covalently; amino acids
-
In all organisms, the AUG codon codes for:
the initiation of translation.
-
The enzyme peptidyl transferase, which catalyzes the transfer of the polypeptide chain attached to the tRNA in the ____________ site to the aminoacyl-tRNA in the ____________ site, is thought to be a(n) ____________ molecule and not a protein.
P; A; rRNA
-
Following peptide bond formation between the amino acid in the A site on the ribosome and the growing polypeptide chain, the tRNA in the A site:
forms a peptide bond with A site of the ribosome.
-
A polyribosome is:
a complex of many ribosome and an mRNA.
-
Interrupted coding sequences include long sequences of bases that do not code for amino acids. These noncoding sequences, called ____________, are found in ____________ cells.
introns; eukaryotic
-
Introns in pre-mRNA are known to:
undergo excision, whereby they are spliced out of the message.
-
A gene can now be defined as:
a DNA sequence that carries information to produce a specific RNA or protein product.
-
Frameshift mutations result from:
the insertion or deletion of one or two base pairs.
-
Genes that encode proteins that are always needed are called:
constitutive genes.
-
The gene that codes for the repressor protein of the E. coli lactose operon is:
constitutive.
-
The molecular switch that controls gene expression is known as:
repressor.
-
Lactose induces the transcription of the lactose operon by:
binding to the allosteric site of the repressor after being converted to allolactose.
-
Bacterial enzymes that are part of a rarely used catabolic pathway are usually organized into a(n) ________________.
inducible operon
-
A repressible operon is usually controlled by:
being turned “on,” usually by the end product of the pathway.
-
In the tryptophan operon, the repressor actively binds to the operator when:
tryptophan binds to an allosteric site on the repressor.
-
cAMP levels decrease when ______________________________. This results in ____________ of CAP.
glucose levels increase; inhibition
-
In the lac operon, cAMP binds to:
catabolite activator protein.
-
The role of CAP in the lac operon is:
enhancement of RNA polymerase binding to the promoter.
-
Translational controls regulate:
the rate at which ribosomes make proteins.
-
Bacterial gene regulation occurs mainly at the _________________ level.
transcriptional
-
Feedback inhibition is:
None of these.
-
Feedback inhibition of the first enzyme of a pathway by the end product of the pathway is an example of:
translational control.
-
Densely staining regions of highly compacted chromatin that are generally not transcribed are:
heterochromatin.
-
DNA sequences that are methylated by a cell are usually genes that:
are inactive.
-
A TATA box is seen in ______________ cells and is the site where _______________________.
eukaryotic; RNA polymerase binds
-
Upstream promoter elements in eukaryotes are:
proteins that inhibit RNA polymerase binding to the promoter.
-
Gene amplification involves:
extra replication of genes that specify a certain gene product only in cells needingthis product.
-
Some eukaryotic DNA sequences act as introns in the cells of some tissues and exons in the cells of other tissues. This allows:
formation of different types of closely related proteins.
-
Splicing together DNA from 2 different organisms is called:
recombinant DNA technology.
-
The modification of the DNA of an organism to produce new genes withnew traits is most properly called:
genetic engineering.
-
The use of organisms to develop useful products is called:
biotechnology.
-
Bacteriophages are:
viruses that infect bacteria.
-
A ____________ is required to transfer genes from one organism toanother.
vector
-
Transformation is a process whereby:
plasmids are transferred into bacterial cells.
-
DNA ligase links two ____________ DNA fragments by ____________ bonds.
linear; covalent
-
The amplification of recombinant plasmids occurs by:
the process of growth and division of the host cell.
-
In polymerase chain reaction technology, the two strands of DNA areseparated by:
heating them.
-
____________ is a technique that can be used to separate DNA molecules
PCR
-
The chain termination method is used in:
gel electrophoresis.
-
If a protein-coding gene is identified, its function can be studied by using RNA interference to ______________.
turn the gene off
-
Why is insulin produced by genetically engineered E. coli cells superior to insulin obtained from animal sources?
It contains human rather than animal sequences, reducing the chances of an allergic response.
-
Introducing a gene for a surface protein produced by a disease-causing agent into a nonpathogenic vector is a method to:
produce a recombinant vaccine.
-
The FBI currently determined an individual’s DNA profile using:
13 STR markers.
-
Retroviruses make _________ by the process of ________.
DNA copies of RNA; reverse transcription
-
An organism in which foreign genes have been incorporated is called a:
transgenic organism.
-
Transgenic organisms are used to aid studies of:
All of these.
-
_______ is an example of a plant that is genetically modified to produce high quantities of β-carotene for conversion to vitamin A.
Rice
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