C4 Sample Questions from Brock Flashcards
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.
A) mRNA has a very short half-life.
mRNA is rapidly degraded in most cells, ensuring that protein synthesis is responsive to changing cellular needs. This short lifespan is crucial for regulating gene expression.
The functional unit of genetic information is the
A) nucleotide.
B) gene.
C) chromosome.
D) protein.
B) gene.
The gene is the basic physical and functional unit of heredity. It carries information for a specific trait or characteristic. While nucleotides are the building blocks of DNA and RNA, and chromosomes are structures containing DNA, the gene is the specific sequence that codes for something.
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.
B) at a lower temperature than GC-rich DNA.
A-T base pairs have two hydrogen bonds, while G-C base pairs have three. It takes more energy (higher temperature) to break the three hydrogen bonds of G-C pairs, so AT-rich DNA denatures at a lower temperature.
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.
D) Archaea and Eukarya have very similar RNA polymerases that are different than bacterial RNA polymerases.
These drugs target bacterial RNA polymerase specifically, which is structurally distinct from archaeal and eukaryotic RNA polymerases.
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.
C) Plasmids contain genes that are NOT essential for cellular growth and replication.
Chromosomes carry essential genes, while plasmids carry genes that may offer advantages in certain environments (like antibiotic resistance) but are not required for basic survival.
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.
A) chromosomes.
Essential genes for basic cellular functions are located on the chromosome to ensure their stable inheritance.
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.
B) The 23S rRNA catalyzes peptide bond formation in the growing polypeptide chain.
The 23S rRNA within the large ribosomal subunit acts as a ribozyme, catalyzing the formation of peptide bonds.
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.
D) excessive heat.
Heat shock proteins, a type of chaperone, are produced in response to heat stress to help protect proteins from denaturation.
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.
C) encodes for essential functional genes.
Chromosomes carry genes essential for basic cellular functions, while plasmids carry non-essential genes.
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.
A) segments of DNA that move from one site to another.
Transposable elements, also known as “jumping genes,” can move within a genome.
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.
C) that confer resistance to antibiotics.
Plasmids often carry genes that provide advantages in specific environments, such as antibiotic resistance.
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.
A) The DNA sequence likely functions as a ribosome-binding site.
If mRNA is produced but few proteins are made, the problem likely lies in translation initiation, which involves the ribosome binding to the mRNA.
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.
C) the protein is secreted and folds outside of the cell.
The N-terminal signal sequence is often cleaved off during protein secretion.
Transcription in eukaryotes occurs in the
A) RNA polymerase.
B) endoplasmic reticulum.
C) cytoplasm.
D) nucleus.
D) nucleus.
Transcription occurs in the nucleus of eukaryotic cells.
T/F: Most prokaryotic genomes are double-stranded circular DNA.
True. Most prokaryotic genomes consist of a single, circular chromosome.
