All Biochemistry Resources
Example Questions
Example Question #9 : Transcription
Which of the following is a ribozyme?
RNase H
RNA polymerase II
All of these are ribozymes
Guanyltransferase
RNase P
RNase P
RNase H is involved in reverse transcriptase, but it is not a ribozyme. RNase P is a ribonuclease that cleaves/processes rRNA and generates 5' ends. The RNA component of RNase P is its catalytic subunit.
Example Question #31 : Nucleic Acid Synthesis
Within a eukaryotic chromosome, which of the following pairs of processes can occur at the same time?
Replication and splicing
Transcription and translation
Transcription and splicing
Translation and splicing
Replication and transcription
Transcription and splicing
In eukaryotes, transcription and splicing could occur simultaneously. Both of these processes take place in the nucleus of the cell, while translation takes place in the cytoplasm. Therefore, translation could not happen at the same time as either transcription or splicing. Replication occurs totally independently from all of the other processes listed.
Example Question #51 : Anabolic Pathways And Synthesis
Oftentimes, biochemists say that the genetic code is degenerate. What are they referring to when they say this?
The sequence of one type of molecule is able to code for the sequence of another type of molecule
The same genetic code is not shared by all species
A change in the reading frame alters expression of all subsequent codons
Some codons are able to code for more than just one amino acid
Some amino acids can be coded for by more than just one codon
Some amino acids can be coded for by more than just one codon
While some of these answer choices are true, others are false. But even for the choices that are true, only one of them directly answers the question. Let's go ahead and look at each choice.
- Some amino acids can be coded for by more than just one codon
This is a true statement, and is also the correct answer. The degeneracy of the code is due to the fact that, for some amino acids, a number of different codons can result in the same amino acid. For example, the amino acid tyrosine can be coded for by either UAU or by UAC.
- A change in the reading frame alters expression of all subsequent codons
While this is a true statement, it does not answer the question. Nonetheless, it's important to know that mutations which either insert or delete a nucleotide will change the entire rest of the reading frame. Consequently, there are likely to be many errors and the resultant polypeptide will likely not be functional.
- Some codons are able to code for more than just one amino acid
This is a false statement. But be careful. This answer choice looks a lot like the correct one. The difference is that, for this choice, we're talking about a single codon being able to code for more than one amino acid. This is not the case.
- The sequence of one type of molecule is able to code for the sequence of another type of molecule
This is a true statement with regards to gene expression. For transcription, the DNA (sequence of deoxyribonucleotides) serves as a template for the formation of mRNA (sequence of ribonucleotides). And for translation, that same mRNA serves as a precursor for the formation of a polypeptide (sequence of amino acids).
- The same genetic code is not shared by all species
From what we know, this is a false statement. The genetic code is universal, meaning that all living things have been found to have the same codon-amino acid relationship.
Example Question #52 : Anabolic Pathways And Synthesis
When biochemists says that genes can be in either direction of the DNA, what do they mean?
The template for transcription can be found on either strand of DNA
Genes can be found both in the middle and at ends of a chromosome
The different alleles for a given gene within chromosomes can be partitioned to either of two cells during mitosis
Genes can be transcribed in both directions, from and
The template for transcription can be found on either strand of DNA
The saying that genes can run in either direction is referring to how they can be expressed. Genes can be found on either strand of the DNA molecule. Since these two strands run antiparallel to one another, the genes being read on one strand would be read in the opposite direction on the other strand.
Genes can also be located on various loci within a given chromosome. Also, it is true that genes assort independently during cell division, but this doesn't answer the question. Also, genes can only be read in the direction. They can never be read in the direction. This is because DNA polymerase, the enzyme responsible for elongating the chain, can only add nucleotides to a chain that has a hydroxyl group at the position.
Example Question #31 : Nucleic Acid Synthesis
Reverse transcriptase is an enzyme that produces DNA molecules from RNA. Which of the following is correct?
Retroviruses have this enzyme and use it to replicate their RNA genome
In eukaryotes reverse transcriptase is encoded by retrotransposons
Reverse transcriptase activity is present in DNA viruses
All of these
Telomerase (the enzyme that maintains telomere length in eukaryotes) has reverse transcriptase activity
All of these
The reverse transcriptase activity of retroviruses like HIV is used to replicate their RNA genome in the host cell. This activity is not needed or present in DNA viruses which can use the host's enzymes to replicate. The reverse transcriptase activity of telomerases is used to prevent telomere ends shortening after multiple replications in somatic cells. Telomeres are short sequences at the end of chromosomes that prevent deterioration of the chromosomes. Retrotransposones are elements that amplify repetitive sequences in the DNA of eukaryotes.
Example Question #32 : Nucleic Acid Synthesis
What is the name of the process in which RNA is converted to DNA?
Replication
Reverse translation
Translation
Transcription
Reverse transcription
Reverse transcription
For biochemical purposes, it is important to have an understanding of the "Central Dogma" of molecular biology. DNA multiplies via replication, is turned into RNA via transcription, and finally to proteins via translation. Going back to DNA from RNA is known as reverse transcription, and is the correct answer. The term "reverse translation" can refer to an aspect of cloning, but does not naturally occur.
Example Question #33 : Nucleic Acid Synthesis
Which of the following matches is correct regarding eukaryotic termination of transcription?
The mRNA cap is added to the 3' end of mRNA
The mRNA cap and the Poly A tail are added to the 3' end of mRNA
The mRNA cap and the poly A tail are added to the 5' end of mRNA
The poly A tail is added to the 3' end of mRNA
The poly A tail is added to the 5' end of mRNA
The poly A tail is added to the 3' end of mRNA
After transcription, mRNA is modified so that it can be preserved for a longer time in the cell. A nucleotide cap structure is attached to the 5' end of the mRNA and a poly A tail is attached to the 3' end of the mRNA in order to accomplish this goal.
Example Question #34 : Nucleic Acid Synthesis
What is the likely genetic make-up of a virus which contains a RNA-dependent RNA polymerase?
Single-stranded DNA
Minus-strand RNA
Plus-strand RNA
Double-stranded RNA
Double-stranded DNA
Minus-strand RNA
We're given the type of enzyme contained within a virus, and we're asked to make a determination of the virus' genetic makeup.
To begin with, we're told that the enzyme is an RNA-dependent RNA polymerase. The name of the enzyme gives us insight into what it does. It requires RNA as a template to produce more RNA.
So if this enzyme can convert RNA into RNA, where does the original RNA come from? The answer is that it must come from the virus. This means that we must be dealing with single-stranded RNA.
Now, the question is to determine the sense of the RNA genome of the virus. That is to say, it can be minus or plus. A minus-sense RNA is one whose complementary sequence can be translated into protein. A plus-sense RNA is one that doesn't need any processing to be translated. Rather, plus-sense RNA can be translated right away. Since we know that the enzyme present is going to produce RNA from RNA, we can then reason that the viral genome is likely minus-sense. When the minus-sense RNA is enacted on by this enzyme, the result is a new strand of RNA that can be translated into protein to serve the needs of the virus.
Example Question #35 : Nucleic Acid Synthesis
What is the relationship of the RNA transcript to the DNA template strand?
I. The RNA transcript is antiparallel to the DNA template strand.
II. The RNA transcript is complementary to the DNA template strand.
III. The RNA transcript is identical to the DNA template strand.
IV. In the RNA transcript, thymine is replaced with uracil.
I, II, and IV
I, II, and III
I and II
I, III, and IV
I and IV
I, II, and IV
The RNA transcript contains nucleotide bases at each position, which are complementary to the DNA. RNA is synthesized in the 5' to 3' direction from a DNA template strand with antiparallel direction (3' to 5').The coding DNA strand is identical to the RNA transcript with the exception that thymine is replaced with uracil in RNA.
Example Question #36 : Nucleic Acid Synthesis
How does initiation of transcription occur in eukaryotes?
I. In eukaryotes sigma protein factor is not required for transcription to occur.
II. Transcription factors such as TFIID bind and activate the gene promoter.
III. RNA polymerase II recognizes and binds the promoter of the gene to be transcribed.
I and II
II and III
I only
I, II, and III
III only
I, II, and III
Eukaryotes have three types of RNA polymerase, I, II, and III. RNA polymerase II recognizes the promoter and binds to the promoter forming a preinitiation complex. The polymerase is composed of 10-12 subunits. Transcription factors also bind the promoter (the region of DNA upstream of the start or origin of transcription).In eukaryotes sigma protein factor is not required for transcription to occur.
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