C4 Brock Sample Questions

Question 1

The functional unit of genetic information is the
A) nucleotide.
B) gene.
C) chromosome.
D) protein.

Answer 1

B) gene.

A gene is considered the functional unit of genetic information because it encodes the instructions for making a specific protein or functional product.

Question 2

Which of the following statements is TRUE concerning mRNA?
A) mRNA has a very short half-life.
B) mRNA has complex secondary structure.
C) mRNA is catalytic.
D) mRNA is the product of translation.

Answer 2

A) mRNA has a very short half-life.

Many mRNA molecules have short half-lives, which allows for rapid response to changes in the cell’s environment by altering gene expression.

Question 3

DNA-binding proteins interact predominantly within which portion of a double-stranded DNA helix?
A) major groove
B) minor groove
C) 3ʹ end
D) supercoil

Answer 3

A) major groove

The major groove of the DNA double helix provides a wider and more accessible space for DNA-binding proteins to interact with specific DNA sequences.

Question 4

AT-rich DNA will denature/melt
A) at a higher temperature than GC-rich DNA.
B) at a lower temperature than GC-rich DNA.
C) usually at the same temperature as GC-rich DNA, with some minor variations.
D) in accordance with the animal or plant from which it was taken.

Answer 4

B) at a lower temperature than GC-rich DNA.

AT base pairs have two hydrogen bonds, whereas GC base pairs have three. This makes AT-rich DNA more easily denatured (melted) at lower temperatures due to the weaker interactions.

Question 5

Supercoiling is important for DNA structure, because
A) it holds together the antiparallel strands of DNA in the double helix.
B) it provides energy for transcription.
C) it condenses the DNA so that it can fit inside the cell.
D) it prevents RNA from pairing with DNA in the double helix.

Answer 5

C) it condenses the DNA so that it can fit inside the cell.

Supercoiling helps to pack DNA into a smaller space, making it possible for the lengthy molecule to fit within the cell’s nucleus or the prokaryotic cell.

Question 6

Many pharmaceutical drugs specifically inhibit transcription in Bacteria but not Archaea or Eukarya. Why would drugs that inhibit transcription only affect Bacteria and not Archaea even though they are both prokaryotes?
A) Archaea and Eukarya have very similar ribosomes that are different than bacterial ribosomes.
B) Bacteria lack a nucleus.
C) Archaea lack operons.
D) Archaea and Eukarya have very similar RNA polymerases that are different than bacterial RNA polymerases.

Answer 6

D) Archaea and Eukarya have very similar RNA polymerases that are different than bacterial RNA polymerases.

The specificity of these drugs towards bacterial transcription is largely due to differences in RNA polymerase structure between bacteria and the other two domains of life.

Question 7

How are plasmids different than chromosomes?
A) Plasmids are always small, linear pieces of DNA. B) Plasmids are composed of single-stranded DNA.
C) Plasmids contain genes that are NOT essential for cellular growth and replication.
D) `Plasmids carry unimportant genes that are of little significance for the ecology and metabolism of an organism.

Answer 7

C) Plasmids contain genes that are NOT essential for cellular growth and replication.

While not exclusively true in all cases, plasmids often carry accessory genes that provide advantageous but non-essential traits, distinguishing them from chromosomes which carry essential genes.

Question 8

Genes that are encoded for polymerases, gyrases, ribosomal proteins, and other proteins essential to replication, transcription, and translation are present on
A) chromosomes.
B) plasmids.
C) chromosomes and plasmids.
D) neither chromosomes nor plasmids.

Answer 8

A) chromosomes.

Essential genes for basic cellular processes like replication, transcription, and translation are typically found on chromosomes, ensuring their presence and stability in the cell.

Question 9

The precursor of each new nucleotide in a strand of DNA is a
A) deoxynucleoside 5ʹ-diphosphate.
B) deoxynucleoside 3ʹ-diphosphate.
C) deoxynucleoside 5ʹ-triphosphate.
D) deoxynucleoside 3ʹ-triphosphate.

Answer 9

C) deoxynucleoside 5ʹ-triphosphate.

dNTPs (deoxynucleoside triphosphates) are the direct precursors for DNA synthesis, providing the energy for phosphodiester bond formation.

Question 10

DNA replication always proceeds in only one direction because the of the incoming nucleotide is attached to the free of the growing DNA strand.
A) 5ʹ-phosphate / 3ʹ-hydroxyl
B) 3ʹ-phosphate / 5ʹ-hydroxyl
C) 5ʹ-deoxyribose / 3ʹ-base
D) 3ʹ-base / 5ʹ-deoxyribose

Answer 10

A) 5ʹ-phosphate / 3ʹ-hydroxyl

DNA synthesis proceeds in the 5’ to 3’ direction because DNA polymerase adds new nucleotides to the 3’-hydroxyl end of the growing strand, attaching to the 5’-phosphate of the incoming nucleotide.

Question 11

Which of the following is formed on the lagging strand during DNA synthesis?
A) DNA secondary structures
B) Okazaki fragments
C) RNA polymerase
D) replisomes

Answer 11

B) Okazaki fragments

Due to the antiparallel nature of DNA and the unidirectional synthesis, the lagging strand is synthesized discontinuously as short segments known as Okazaki fragments.

Question 12

The template for RNA polymerase is _______, and the new RNA molecule is ________ to the template.
A) an independent RNA segment / parallel and identical
B) DNA / antiparallel and complementary
C) an independent RNA segment / antiparallel and complementary
D) DNA / parallel and identical

Answer 12

B) DNA / antiparallel and complementary

RNA polymerase uses DNA as a template, and the synthesized RNA strand is antiparallel and complementary to the DNA template strand.

Question 13

In the process of transcription, promoters are specific sequences of that are recognized by ________.
A) DNA / DNA polymerase
B) RNA / DNA polymerase
C) DNA / sigma factors
D) RNA / ribosomes

Answer 13

C) DNA / sigma factors

Sigma factors, part of the RNA polymerase holoenzyme in prokaryotes, recognize and bind to specific DNA sequences known as promoters to initiate transcription.

Question 14

An example of correct nucleotide pairing is
A) T and U.
B) G and U.
C) A and T.
D) C and U.

Answer 14

C) A and T.

In DNA, adenine (A) pairs with thymine (T) through two hydrogen bonds.

Question 15

Stop codons are also called codons.
A) nonsense
B) release factor
C) degeneracy
D) conversion

Answer 15

A) nonsense

Stop codons are often referred to as nonsense codons because they do not code for any amino acid, instead signaling the termination of protein synthesis.

Question 16

Transfer RNA (tRNA) molecules
A) function to transfer ribonucleotides to RNA polymerase during transcription.
B) function to transfer the correct amino acids to the ribosome during translation.
C) contain codons that bind to ribosomes during translation.
D) are only present in the nucleus or eukaryotes.

Answer 16

B) function to transfer the correct amino acids to the ribosome during translation.

The primary role of tRNA is to act as an adaptor molecule, linking the language of nucleotides to the language of amino acids by bringing the correct amino acid to the ribosome during protein synthesis.

Question 17

tRNA is released from the ribosome at the site.
A) P
B) A
C) R
D) E

Answer 17

D) E

The E (Exit) site is where the tRNA, after donating its amino acid to the growing peptide chain, is released from the ribosome.

Question 18

Which statement is TRUE regarding protein synthesis?
A) Ribosomal proteins catalyze peptide bond formation in the growing polypeptide chain.
B) The 23S rRNA catalyzes peptide bond formation in the growing polypeptide chain.
C) Transfer RNAs catalyze peptide bond formation in the growing polypeptide chain.
D) Messenger RNA catalyzes peptide bond formation in the growing polypeptide chain.

Answer 18

B) The 23S rRNA catalyzes peptide bond formation in the growing polypeptide chain.

In the ribosome, the 23S rRNA (part of the large subunit) plays a crucial catalytic role in forming peptide bonds between amino acids.

Question 19

The Tat system is involved in
A) protein synthesis.
B) transcriptional initiation.
C) protein folding.
D) protein secretion.

Answer 19

D) protein secretion.

The Twin-arginine translocation (Tat) system is a protein transport system that secretes folded proteins across the cytoplasmic membrane in bacteria.

Question 20

In all cells, genes are composed of
A) nucleic acids.
B) mRNA.
C) proteins.
D) chaperones.

Answer 20

A) nucleic acids.

Genes, by definition, are sequences of nucleic acids (DNA or, in some viruses, RNA) that encode information.

Question 21

Which of the following is an example of one codon?
A) CATT
B) GCCATT
C) CAG
D) CCGUAA

Answer 21

C) CAG

A codon is a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule. CAG is a specific example of a codon.

Question 22

In all cells a gene encodes for
A) a protein (via mRNA).
B) a tRNA.
C) an rRNA.
D) a protein, tRNA, or rRNA depending on the specific gene.

Answer 22

D) a protein, tRNA, or rRNA depending on the specific gene.

While many genes encode proteins, others encode functional RNA molecules like tRNA and rRNA, which are crucial for protein synthesis.

Question 23

Which of the following is NOT correct regarding DNA and RNA synthesis?
A) The overall direction of chain growth is from the 5ʹ to 3ʹ end.
B) Both processes require an RNA primer to begin.
C) The template strand is antiparallel to the newly synthesized strand.
D) DNA is the template for both DNA and RNA synthesis.

Answer 23

D) DNA is the template for both DNA and RNA synthesis.

While DNA serves as the template for DNA replication and transcription (RNA synthesis), RNA can also serve as a template for certain processes (e.g., reverse transcription in retroviruses).

Question 24

Termination of RNA synthesis is ultimately determined by
A) exhaustion of RNA polymerase activity.
B) special protein factors.
C) terminases.
D) specific nucleotide sequences on the template strand.

Answer 24

D) specific nucleotide sequences on the template strand.

Termination of transcription is often signaled by specific DNA sequences that, when transcribed into RNA, trigger the release of the newly synthesized RNA from the RNA polymerase.

Question 25

GTP provides energy for
A) transcription.
B) translation.
C) DNA replication.
D) protein folding.

Answer 25

B) translation.

During translation, GTP is used as an energy source for the translocation step, where the ribosome moves along the mRNA.

Question 26

Transcription of chaperones is greatly accelerated when a cell is stressed by
A) excessive osmotic pressure.
B) extremes in pH value.
C) lack of oxygen.
D) excessive heat.

Answer 26

D) excessive heat.

Heat shock and other stresses induce the transcription of chaperone genes, whose products help in the proper folding of proteins and protection against stress.

Question 27

The flow of biological information begins with
A) DNA replication.
B) RNA transcription.
C) mRNA translation.
D) transcriptional regulation.

Answer 27

C) mRNA translation.

Given the provided options and focusing on the flow into protein synthesis, translation is the process where mRNA’s information is used to build proteins. However, the traditional start of genetic information flow is DNA (replication/transcription), not listed as an option.

Question 28

DNA participates in protein synthesis through
A) cyclic messengers.
B) direct pairing with amino acids.
C) an RNA intermediate.
D) protein folding.

Answer 28

C) an RNA intermediate.

DNA’s information is first transcribed into mRNA, which then serves as the template for protein synthesis during translation.

Question 29

The two strands of the DNA double helix are held together by
A) 5ʹ to 3ʹ attraction.
B) hydrogen bonds between nucleotide bases.
C) codons.
D) peptide bonds between nucleotide bases.

Answer 29

B) hydrogen bonds between nucleotide bases.

Hydrogen bonding between the bases (A-T and G-C) of the two strands stabilizes the DNA double helix.

Question 30

In Bacteria, a chromosome can be distinguished from a plasmid, because a chromosome is a genetic element that
A) is circular.
B) is linear.
C) encodes for essential functional genes.
D) replicates via a bidirectional fork.

Answer 30

C) encodes for essential functional genes.

Bacterial chromosomes typically carry genes essential for survival, growth, and reproduction, distinguishing them from plasmids, which often carry accessory genes.

Question 31

Transposable elements are
A) segments of DNA that move from one site to another.
B) transcribed genes.
C) segments of RNA that are involved in transposing DNA into proteins.
D) proteins that aid in the secretion of enzymes out of the cell.

Answer 31

A) segments of DNA that move from one site to another.

Transposable elements (transposons) are DNA sequences that can change their location within a genome, affecting genetic diversity and gene regulation.

Question 32

In complementary base pairing of DNA, adenine pairs with ___________ (or _________ in RNA) and cytosine always pairs with ________.
A) guanine / uracil / thymine
B) uracil / thymine / guanine
C) thymine / guanine / uracil
D) thymine / uracil / guanine

Answer 32

D) thymine / uracil / guanine

In DNA, A pairs with T, and C pairs with G. In RNA, A pairs with U (instead of T), and C still pairs with G.

Question 33

The function of the DNA polymerase is to catalyze
A) the addition of deoxynucleotides.
B) the formation of RNA primers.
C) the addition of ribonucleotides.
D) hydrogen bonding between complementary base pairs.

Answer 33

A) the addition of deoxynucleotides.

DNA polymerase is the enzyme responsible for adding deoxynucleotides to a growing DNA chain during replication and repair.

Question 34

DNA replication is started with a(n) _______, which, in most cases, in vivo is a short stretch of ________.
A) promoter / DNA
B) mRNA / RNA
C) primer / RNA
D) ribosome-binding sequence / DNA

Answer 34

C) primer / RNA

DNA replication initiates with an RNA primer, a short RNA sequence that provides a starting point for DNA synthesis.

Question 35

The function of RNA polymerase is to
A) catalyze the formation of phosphodiester bonds between deoxyribonucleotids.
B) catalyze the formation of phosphodiester bonds between ribonucleotides.
C) cleave mRNA to remove introns.
D) activate tRNAs.

Answer 35

B) catalyze the formation of phosphodiester bonds between ribonucleotides.

RNA polymerase is the enzyme responsible for synthesizing RNA from a DNA template by forming phosphodiester bonds between ribonucleotides.

Question 36

An operon is a useful genetic element, because it A) encourages the binding of RNA polymerase.
B) allows coordinated expression of multiple related genes in prokaryotes.
C) translates DNA sequence into amino acid sequence.
D) encourages the binding of ribosomes in the correct location.

Answer 36

B) allows coordinated expression of multiple related genes in prokaryotes.

Operons enable the simultaneous regulation and expression of functionally related genes in prokaryotes, enhancing efficiency in response to environmental changes.

Question 37

Plasmids often encode for proteins
A) involved in translation.
B) required for cellular growth.
C) that confer resistance to antibiotics.
D) involved in DNA replication.

Answer 37

C) that confer resistance to antibiotics.

Many plasmids carry genes that provide bacteria with advantageous traits, such as antibiotic resistance, which can be shared among bacterial cells.

Question 38

The codon on the matches with the anticodon on the to direct the addition of the correct amino acid to the growing polypeptide chain.
A) mRNA / tRNA
B) tRNA / mRNA
C) DNA / mRNA
D) tRNA / rRNA

Answer 38

A) mRNA / tRNA

During translation, mRNA codons are recognized by tRNA anticodons, ensuring the correct amino acids are added to the growing protein chain.

Question 39

The structure and function of a protein are determined by its sequence.
A) nucleotide
B) amino acid
C) ribonucleotide
D) translocation

Answer 39

B) amino acid

The specific sequence of amino acids in a protein dictates its 3D structure and, consequently, its function in the cell.

Question 40

You experimentally change the DNA sequence directly upstream of a start codon of an operon in E. coli to investigate the function of this region of DNA. Analysis reveals that after the change the same amount of mRNA is made from the operon, but there are very few proteins made from the operon. What is the most likely function of the DNA sequence that you changed?
A) The DNA sequence likely functions as a ribosome-binding site.
B) The DNA sequence likely functions as a promoter.
C) The DNA sequence likely functions as a termination sequence.
D) The DNA sequence likely functions as in transcriptional regulation.

Answer 40

A) The DNA sequence likely functions as a ribosome-binding site.

The change affected protein production but not mRNA synthesis, suggesting the altered region is crucial for translation initiation, which is the role of the ribosome-binding site (Shine-Dalgarno sequence in prokaryotes).

Question 41

In ______ several ribosomes can simultaneously translate a single mRNA molecule in a complex called a(n) ______.
A) prokaryotes / polysome
B) eukaryotes / polysome
C) prokaryotes / initiation complex
D) eukaryotes / splicing complex

Answer 41

A) prokaryotes / polysome

In prokaryotes, due to the lack of a nuclear membrane, translation can initiate before transcription is complete, leading to the formation of polysomes, where multiple ribosomes translate the same mRNA simultaneously.

Question 42

You are studying a protein in Salmonella typhimurium that you believe is a toxin. Whenever you attempt to purify the protein from lysed cell cultures, you get two forms of the protein. One form is smaller than the other and is missing 15 amino acids from the N-terminus compared to the larger form. This leads you to hypothesize that
A) there are two termination sites in the mRNA.
B) the protein requires chaperonins to fold properly.
C) the protein is secreted and folds outside of the cell.
D) you need to re-do the experiment because there should only be one form.

Answer 42

C) the protein is secreted and folds outside of the cell.

The presence of two protein forms, one shorter than the other by 15 N-terminal amino acids, suggests the removal of a signal peptide, which is typical for proteins secreted out of the cell. This processing would occur after translation, explaining the two observed forms.

Question 43

Transcription in eukaryotes occurs in the
A) RNA polymerase.
B) endoplasmic reticulum.
C) cytoplasm.
D) nucleus.

Answer 43

D) nucleus.

Unlike prokaryotes, eukaryotic cells have a nucleus, which houses the genetic material and is the site where transcription (the synthesis of RNA from DNA) takes place.

Question 44

During DNA replication Okazaki fragments are linked together by , an enzyme that creates phosphodiester bonds between nicked fragments of DNA.
A) exopolymerase
B) DNA gyrase
C) topoisomerase
D) DNA ligase

Answer 44

D) DNA ligase

DNA ligase is the enzyme responsible for sealing the gaps (nicks) between Okazaki fragments on the lagging strand during DNA replication, creating a continuous strand.

Question 45

A triplet of bases on an mRNA molecule is known as a(n)
A) amino acid.
B) anticodon.
C) codon.
D) ribosome-binding sequence.

Answer 45

C) codon.

In molecular biology, a codon is a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule, specifying an amino acid or termination signal.

Question 46

Each adenine-thymine base pair has ______ hydrogen bonds, while each guanine-cytosine base pair has _____ hydrogen bond(s).
A) two / one
B) two / three
C) four / three
D) three / two

Answer 46

B) two / three

AT base pairs are held together by 2 hydrogen bonds, whereas GC base pairs are held together by 3 hydrogen bonds, contributing to the greater stability of GC-rich DNA.

Question 47

In DNA replication there are leading and lagging strands, because
A) DNA replication is conservative and a completely new DNA molecule must be made.
B) DNA replication is semiconservative and each strand is copied simultaneously in opposite directions.
C) the strands of DNA are parallel and are copied in the same direction simultaneously.
D) one strand of DNA is copied faster than the other.

Answer 47

B) DNA replication is semiconservative and each strand is copied simultaneously in opposite directions.

The semiconservative model of DNA replication, coupled with the unidirectional nature of DNA synthesis, necessitates the simultaneous replication of both strands in opposite directions, resulting in one continuously synthesized leading strand and one discontinuously synthesized lagging strand.

Question 48

Most prokaryotic genomes are double-stranded circular DNA

Answer 48

TRUE

The majority of prokaryotes (e.g., bacteria) indeed have genomes that are double-stranded and circular, although there are exceptions (e.g., some bacteria with linear chromosomes).

Question 49

Inverted repeats are common features of transcription termination sequences in all three domains of life.

Answer 49

TRUE

Inverted repeats (palindromic sequences) are found in termination sequences (e.g., rho-independent terminators) across all domains (Archaea, Bacteria, Eukarya), facilitating hairpin loop formation that helps terminate transcription.

Question 50

In nature, the predominant form of DNA is supercoiled in a negative direction.

Answer 50

TRUE

Most naturally occurring DNA is indeed supercoiled, and in the case of many prokaryotes and some eukaryotic DNA (e.g., mitochondrial DNA), this supercoiling is predominantly in a negative direction, which helps pack the DNA more efficiently.

Question 51

Genes found on plasmids do NOT impact metabolism or cellular structures.

Answer 51

FALSE

Plasmids often carry genes that can significantly impact metabolism (e.g., antibiotic resistance, metabolic pathway genes) and, in some cases, cellular structures (e.g., genes for pili or other surface structures).

Question 52

A plasmid is all the genetic material present in a virus.

Answer 52

FALSE

A plasmid is a small, self-replicating circular DNA molecule found in bacterial and sometimes eukaryotic cells. Viral genetic material, however, can be either DNA or RNA, is not necessarily circular, and is packaged within a viral capsid.

Question 53

DNA replication is bidirectional in prokaryotes with circular chromosomes.

Answer 53

FALSE

While some prokaryotes have circular chromosomes, DNA replication in these organisms is typically unidirectional from a single origin of replication, not bidirectional as seen in some eukaryotes with linear chromosomes.

Question 54

RNA acts at both the genetic and the functional levels.

Answer 54

TRUE

RNA serves at the genetic level as messenger RNA (mRNA) carrying genetic information from DNA to the ribosome. At the functional level, RNA acts as transfer RNA (tRNA) and ribosomal RNA (rRNA), directly participating in protein synthesis, and in some cases, as catalytic RNA (ribozymes).

Question 55

RNA is incapable of forming secondary structure.

Answer 55

FALSE

RNA is fully capable of forming complex secondary structures (e.g., stem-loops, hairpin loops) due to the ability of its nucleotide bases to form hydrogen bonds with each other, which is crucial for its function in cells.

Question 56

Aminoacyl-tRNA synthetase catalyzes the reaction between the appropriate amino acid and ATP to form an activated amino acid: amino acid + ATP ↔ aminoacyl-AMP + P-P.

Answer 56

TRUE

This statement accurately describes the first step in the aminoacylation process, where aminoacyl-tRNA synthetases link amino acids to ATP, forming aminoacyl-AMP, which then attaches to tRNA, preparing it for protein synthesis.

Question 57

The formation of new DNA does NOT require energy.

Answer 57

FALSE

DNA replication requires energy, which is primarily provided by the phosphodiester bond formation between nucleotides, a process driven by the energy released from the hydrolysis of high-energy phosphate compounds like ATP and the nucleotide triphosphates (dNTPs) themselves.

Question 58

rRNA has an enzymatic role in all stages of protein synthesis.

Answer 58

TRUE

As a component of ribosomes, rRNA plays a structural role but also has enzymatic (ribozyme) activity, particularly in the peptidyl transfer reaction, which is crucial for peptide bond formation during protein synthesis.

Question 59

Proteins known as chaperones are found only in Bacteria.

Answer 59

FALSE

Molecular chaperones, which assist in the proper folding of proteins, are found not only in Bacteria but also in Archaea and Eukarya, highlighting their universal importance in maintaining protein homeostasis across all domains of life.

Question 60

Throughout the living world, the genetic code is generally universal; however, there are slight variations.

Answer 60

TRUE

The genetic code, which maps nucleotide sequences to amino acids, is largely universal across different organisms. However, there are known exceptions and variations, particularly in some mitochondria and certain microorganisms.

Question 61

DNA replication involves the synthesis of an RNA primer on one strand of the DNA.

Answer 61

TRUE

DNA replication indeed involves the synthesis of RNA primers, but this occurs on both the leading and lagging strands in the case of circular or linear chromosomes with multiple replication origins. The statement might imply only one strand is involved, which can be misleading.