A nucleotide is composed of a phosphate, a sugar, and one of the four nucleotide bases (adenine, thymine, guanine, or cytosine).
Correct Answer: A phosphate, a sugar, and a nucleotide base
Adenine preferentially binds with thymine because the stereochemistry of their structures favors the formation of two hydrogen bonds with optimal stability. Similarly cytosine pairs with guanine because their structures favor the formation of three hydrogen bonds.
Correct Answer: A preferentially binds to T
The bases in DNA are of two types: the purines (adenine and guanine) and the pyrimidines (thymine and cytosine). Purines are large double-ring structures, whereas the pyrimidines have single rings.
Correct Answer: Adenine and guanine
Topoisomerase is the enzyme that catalyses the clipping of the supercoiled DNA molecule. The clip relieves the strain on the supercoil.
Correct Answer: Topoisomerase
Transcription is the process in which DNA is transcribed into all three types of RNA: messenger RNA, transfer RNA and ribosomal RNA. The process by which DNA copies itself is called replication.
Correct Answer: A new DNA molecule
ATA contains thymine and is therefore only found in DNA (RNA contains uracil instead of thymine).
Correct Answer: Found in DNA
No two base codons exist.
Correct Answer: Found in neither nucleic acid
All codons have three bases.
Correct Answer: Found in both DNA and RNA
AUG, the initiation codon, is present only in RNA (only RNA contains uracil).
Correct Answer: Found in RNA
To start replication, the initiator protein must first recognize the replicator sequence of DNA and bind to it.
Correct Answer: The initiator protein binds to the replicator sequence
To start replication, the initiator protein must first recognize the replicator sequence of DNA and bind to it. This is followed by the partial unwinding of the DNA strands adjacent to that site.
Correct Answer: DNA partly uncoils
To start replication, the initiator protein must first recognize the replicator sequence of DNA and bind to it. This is followed by the partial unwinding of the DNA strands adjacent to that site. Then the entire DNA chromosome is copied.
Correct Answer: The entire DNA chromosome is copied
To start replication, the initiator protein must first recognize the replicator sequence of DNA and bind to it. This is followed by the partial unwinding of the DNA strands adjacent to that site. Then the entire DNA chromosome is copied. Next, the components involved in replication dissociate from the DNA.
Correct Answer: The components involved in replication dissociate from the DNA
To start replication, the initiator protein must first recognize the replicator sequence of DNA and bind to it. This is followed by the partial unwinding of the DNA strands adjacent to that site. Then the entire DNA chromosome is copied. Next, the components involved in replication dissociate from the DNA. At this point, the replicated circular chromosomes are still linked together but must be separated if the daughter cells that result from cell division are to acquire one chromosome each.
Correct Answer: Daughter chromosomes are separated from each other
We refer to genes occurring in DNA, being inherited from one generation to the next and containing information that defines the structure of a protein or RNA.
Correct Answer: A segment of DNA that contains inherited information that defines the structure of a protein or RNA
The two strands of DNA are held together by complementary base pairing between the strands. A new base added to a growing strand must therefore be complementary to the base on the template strand.
Correct Answer: The template strand
DNA polymerase is the enzyme involved in DNA replication. The processivity of DNA polymerase refers to how many bases it can add while it is at the replication fork and so it is associated with the speed of replication.
Correct Answer: The speed of DNA replication
One of the characteristics of DNA polymerase is its proofreading capability. This proof reading minimizes the errors that occur in the replication of DNA.
Correct Answer: Minimizes errors in DNA
DNA strands must separate in order for each strand to be replicated. As the strands separate they form a fork referred to as the replication fork. It is at this location that replication is taking place.
Correct Answer: DNA replication is ongoing
Replication of the leading stand and the lagging strand occur simultaneously, the lagging strand (not the leading strand) is made in pieces, and DNA replication goes from the 5′ to the 3′ direction.
Correct Answer: Made continuously
The lagging strand is replicated in pieces, which are called Okazaki fragments.
Correct Answer: On the lagging strand
DNA ligase joins (ligates) pieces of DNA together. Helicase and topoisomerase unwind DNA, DNA polymerase makes new DNA and RNA polymerase makes new RNA.
Correct Answer: DNA ligase
Transcription is the production of RNA based on a DNA code.
Correct Answer: A new strand of DNA
Transcription involves three steps, initiation, elongation and termination.
Correct Answer: Initiation, elongation and termination
Transfer RNA molecules function as adapters between mRNA attached to a ribosome and the amino protein chain. Each tRNA attaches to a specific amino acid and to a specific codon in the mRNA.
Correct Answer: Only one specific amino acid
The synthesis of proteins encoded by mRNA occurs at the ribosome.
Correct Answer: Translation occurs
Ribosomes are non-membrane-enclosed cytoplasmic structures made up of protein and ribosomal RNA. They are the site of protein production in the cell. Sometimes mRNA and tRNA are attached, but these are not considered part of the structure of RNA.
Correct Answer: Ribosomal RNA and protein
The ribosome has three binding sites for tRNA molecules. The A site is for tRNA carrying a single amino acid. The P site is for peptidyl-tRNA, which is holding on to the growing peptide chain, and the E site is for tRNA that is in the process of exiting from the ribosome.
Correct Answer: Has three sites for translation
A constitutive gene is always turned on.
Correct Answer: Constitutive
An inducible gene is usually turned off, but is turned is on in the presence of certain molecules
Correct Answer: Inducible
For the lac structural genes to be synthesized, RNA polymerase must be able to bind to the lac operon promoter, which can only happen if the lac repressor is not bound to the operator. The lac repressor is prevented from binding to the operator by the presence of the inducer (allolactose).
Correct Answer: Repressor must not bind to the operator
The simplest mutations are switches of one base for another. These are called missense or point mutations because they affect only one base.
Correct Answer: A single base in the RNA
The mutation is a change of UUU to UUC (AUG UUC UCU ACU). Both of these codons code for phenylalanine so there will be no change to the protein sequence. This is called a silent mutation.
Correct Answer: A silent mutation
The change is from UUU to UAA (AUG UAA UCU ACU). This is a stop codon (or stop) and will result in a truncated, non-functional protein. This is called a nonsense mutation.
Correct Answer: A nonsense mutation
The first C has been deleted (AUG UUU U_UA CU). The reading frame shifts from UCU (serine) to UUA (leucine).
Correct Answer: A frameshift mutation
A mutagen is a physical or chemical agent that causes mutations to the genetic material.
Correct Answer: Cause mutations
Ultraviolet radiation can cause DNA damage through the formation of thymine dimers, which are two thymine bases on the same strand of DNA bound to each other. When these bases link together on the same strand, they cause DNA polymerase to stop at that site, and replication stops.
Correct Answer: Ultraviolet radiation
Conjugation is the transfer of genetic material between bacterial cells by joining them together with a sex pilus. The two cells are not related and are alive at the same time so the transfer is not between generations and is said to be horizontal.
Correct Answer: Transfers DNA horizontally, to cells in the same generation
Transposition is a special form of recombination in which segments of DNA (transposons) move from one place on a bacterial chromosome to another.
Correct Answer: A specific form of recombination
Transformation is a form of genetic transfer that involves naked DNA. This DNA is taken up by a bacterial cell and recombines with that cell’s DNA. For this to happen, the recipient cell must be competent, which means that the wall of this cell can accommodate the uptake of large molecules. Conjugation is a different process in which DNA is transferred via a sex pilus.
Correct Answer: All of the choices
Transduction is a common event in both Gram-positive and Gram-negative organisms, and involves the transfer of genetic information using a bacterial virus (known as a bacteriophage). Pilli are involved in conjugation.
Correct Answer: Is carried out by a virus
One of the cells in conjugation must contain an F factor plasmid. This allows the formation of a pilus to connect the two mating cells together to permit the transfer of plasmid DNA.
Correct Answer: An F factor plasmid
Conjugation requires the donor cell to have an F plasmid.
Correct Answer: Dissimilation plasmids