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Example Questions
Example Question #1 : Dna And Rna
Which molecule contains an anticodon region?
rRNA
mRNA
htRNA
tRNA
DNA
tRNA
tRNA carries the anticodon. tRNA is a transfer ribonucleic acid; it is a type of RNA molecule that decodes the mRNA sequence to form a protein. The anticodon is the part of the tRNA structure that complements the mRNA codon, dictating the identity of the amino acid carried by the tRNA and required to build the proper polypeptide chain.
Example Question #2 : Dna And Rna
Which of the following statements about RNA is false?
Hairpin turn structures are composed of two RNA molecules in a parallel configuration
RNA forms intramolecular double helices
None of the other answers is false
A hydroxyl group on the 2’ of riboses makes RNA phosphodiester bonds fragile
mRNA has a half-life shorter than the cell division cycle
Hairpin turn structures are composed of two RNA molecules in a parallel configuration
The presence of an group on the 2’ carbon if ribose does indeed make any phosphodiester bonds at this site subject to hydrolysis. RNA can sometimes form double-helices, such as in tRNA. mRNA is constantly being degraded in the cytoplasm, and so it has a very short half-life relative to the life of the cell. RNA’s hairpin turn structures are composed of only one molecule which has doubled back on itself, rather than two separate molecules.
Example Question #1 : Dna And Rna
Which of the following statements about B DNA are incorrect?
B DNA is the most commonly found double helical structure
B DNA is right handed with 10 base pairs per turn
B DNA has a wide and deep major groove and a narrow and shallow minor groove
B DNA has a diameter of
All of these are correct
B DNA has a wide and deep major groove and a narrow and shallow minor groove
B DNA has a wide and deep major groove and a narrow and deep minor groove. All other statements regarding B DNA are true.
Example Question #1 : Dna And Rna
1. chromosome
2. solenoid
3. nucleosome
4. radial loop
5. base pair
6. nucleotide
Place the above structures in order from smallest to largest.
The correct order is base pair, nucleotide, nucleosome ("bead on a string"), solenoid, radial loop, chromosome. A solenoid is created by the packing of DNA with multiple nucleosomes, and a radial loop is compacted even further in chromatin.
Example Question #1 : Dna And Rna
Two strands of DNA were isolated from a solution, named DNA-1 and DNA-2. DNA-2 was found to have a higher melting point (temperature at which the two strands break apart). What can we conclude about the two strands' nucleotide composition?
DNA-1 has a higher guanine and cytosine concentration
DNA-2 has a higher adenine and thymine concentration
DNA-1 has a higher adenine and thymine concentration
DNA-2 has a higher guanine and cytosine concentration
DNA-2 has a higher guanine and cytosine concentration
Recall that guanine and cytosine form three hydrogen bonds to one another in DNA, while adenine and thymine only form two hydrogen bonds to one another. This means that DNA strands with higher concentrations of guanine and cytosine will be more stable, and thus require greater energy to break apart. In this case, since DNA-2 required more energy (higher temperature) to denature, it has a higher concentration of guanine and cytosine.
Example Question #13 : Nucleic Acid Structures And Functions
Transcription is initiated when RNA polymerase binds to the DNA at the __________. (In humans, this is known as the TATA box).
initiator
operator
promoter region
poly-A tail
start codon
promoter region
The promoter region is a short segment of DNA that is recognized and bound to by RNA polymerase prior to transcription. The promoter region is usually upstream of the operator and will not be transcribed into mRNA.
Example Question #1 : Dna And Rna
Which of the following statements concerning DNA packing is incorrect?
More than one of these are incorrect
Histones are rich in the amino acids Asp and Glu, giving them a net negative charge
Nucleosomes appear as "beads on a string" when viewed under a microscope
Joining two units of H2A, H2B, H3, and H4 all together forms a histone octamer
A nucleosome is a histone with DNA coiled around it, allowing for extremely efficient DNA packing
Histones are rich in the amino acids Asp and Glu, giving them a net negative charge
Histones are rich in the amino acids Asp Lys and Glu Arg, giving an overall net negative positive charge. (Because DNA is negatively charged, this allows for tighter binding between the histones and coiled DNA).
Example Question #1 : Dna And Rna
Which of the following is a difference between DNA and RNA?
The sugar of DNA is glucose and the sugar of RNA is fructose
DNA is only found in prokaryotes and RNA is found in eukaryotes
DNA has a as opposed to a
on carbon two
RNA contains sulfur and DNA contains phosphate
DNA has a as opposed to a
on carbon two
DNA's sugar is deoxyribose, which involves the lack of a hydroxyl group on the second cabon. RNA's sugar is ribose. DNA and RNA is found in both prokaryotes and eukaryotes and both contain phosphate and neither contain sulfur.
Example Question #2 : Dna And Rna
What enzyme involved DNA replication has a 3'-5' proofreading exonuclease activity to help ensure fidelity in replication of DNA?
Primase
Helicase
DNA polymerase III
DNA polymerase I
DNA ligase
DNA polymerase III
DNA polymerase III is the only DNA replication enzyme with proofreading (3'-5' exonuclease) capabilities. Ligase links Okazaki fragments. Helicase unwinds the two DNA strands. DNA polymerase I contains 5'-3' exonuclease activity, but this is involved in primer removal, not proofreading. Primase is a type of RNA polymerase.
Example Question #3 : Dna And Rna
The primosome remains that are associated with the lagging strand in DNA replication are known as which of the following?
Primase fragments
DNA ligase
DNA polymerase III
DNA polymerase I
Okazaki fragments
Okazaki fragments
Okazaki fragments are found in the lagging strand, and are linked by DNA ligase. These short fragments of DNA are formed because DNA polymerase III (the main polymerizing enzyme complex) can only add nucleotides the the 3' end of a DNA strand. Since DNA strands are antiparallel, this is unavoidable.
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