Q&A Hero

Q: Optical density and viable cell concentration are LEAST proportional to each other during A) lag phase. B) exponential growth phase. C) stationary phase. D) death phase.

Q: The time between inoculation and the beginning of growth is usually called the A) lag phase. B) log phase. C) dormant phase. D) death phase.

Q: Enumerating cells in a biofilm is especially challenging for A) microscopic direct counting. B) measuring turbidity. C) viability counts with spread plating. D) microscopic direct county, measuring turbidity, and viability counts with spread plating.

Q: The time interval required for the formation of two cells from one is called the A) generation time. B) growth time. C) growth rate. D) division rate.

Q: A bacterium that lacks the mreB gene will have a ________ shape. A) bacillus B) coccoid C) short bacillus D) vibrio

Q: The process by which two cells arise from one is known as A) conjugation. B) binary fission. C) meiosis. D) mitosis.

Q: Which is most abundant and active in divisome complexes? A) FtsZ B) DNA replication forks C) MinCD D) MreB

Q: Which of the following is/are transferred to daughter cells during cell division? A) genomic DNA, the blueprint for everything the cell needs B) individual genes and enzymes to later be brought together to form the genome C) chromosome and enzymes to immediately begin cellular metabolism D) chromosome, proteins, and all other cellular constituents

Q: Explain why GC-rich DNA requires a higher temperature to denture or melt than AT-rich DNA and hypothesize as to why the GC content of chromosomes in microorganisms from different environments varies widely.

Q: Speculate on why it can be problematic to copy and express genes from Bacteria into Eukarya.

Q: Speculate why the half-life of mRNA is short, while the half-lives of rRNA and tRNA are long.

Q: Explain how Escherichia coli can grow with a doubling time of 20 minutes when chromosome replication takes 40 minutes.

Q: You are trying to design a protein that will be expressed in Escherichia coli and secreted outside of the cell for purification and use as a pharmaceutical. E. coli is a gram-negative cell and the protein folds after it has exited the cell. Which secretion system would work best for this project? Support your answer with evidence based on the properties of E. coli, the protein, and the secretion system.

Q: Is the following statement TRUE or FALSE? Explain why you think so. "Proteins are the only biomolecules capable of catalyzing bond formation."

Q: Describe protein synthesis in terms of initiation, elongation, and termination/release.

Q: How is an open reading frame (ORF) identified and used to determine the sequence of amino acids in the gene it encodes for?

Q: Explain the difference between an intrinsic terminator and a Rho-dependent termination site.

Q: Explain the process of RNA transcription using the terms upstream, Pribnow box, and consensus sequence.

Q: Explain the role of sigma factors in RNA synthesis in Bacteria.

Q: Some essential genes and DNA sequences in cells DO NOT encode for proteins but are still essential for cellular growth and replication. Give two examples of a gene or sequence of which this is true and explain why it is essential for growth or replication.

Q: Explain the function of the helicases and why they are necessary.

Q: Discuss how the initiation of DNA synthesis occurs in bacteria using the terms origin of replication, replication fork, and theta structures.

Q: Explain the concept of semiconservative replication and how simultaneous copying of both strands of DNA is accomplished in prokaryotic cells.

Q: Explain the difference between transcription and translation and how the processes differ in bacteriaand eukaryotes.

Q: What is the basic flow of genetic information in all cellular life? Include in your answer a diagram that illustrates the relationships between the basic components and steps in the flow of genetic information.

Q: The following is the sequence of bases in the sense strand of a DNA segment and contains the beginning of a gene. DNA 3' A T A T T A C C A G G C A T G G A C C C C C G G G 5' Based on this sequence, write the sequence of the anti-sense DNA strand and the mRNA. Label the 5' and 3' ends in your predicted sequences. The start codon in this organism is AUG. Indicate where the start codon is in your sequence. Why is the start codon important? Why does there have to be a specific start codon?

Q: You isolate a piece of DNA from a microorganism you cultivated from your teeth. The piece of DNA is 94 kbp is size and is circular. You sequence it and discover that it contains genes for capsule formation, pili, and antibiotic resistance, as well as an origin of replication. What is this piece of DNA and how is it related to the other genetic elements found in prokaryotic cells?

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

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

Q: Proteins known as chaperones are found only in Bacteria.

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

Q: The formation of new DNA does NOT require energy.

Q: 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.

Q: RNA is incapable of forming secondary structure.

Q: RNA acts at both the genetic and the functional levels.

Q: DNA replication is bidirectional in prokaryotes with circular chromosomes.

Q: The genetic material in a virus is technically called a plasmid.

Q: Genes found on plasmids DO NOT impact metabolism or cellular structures.

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

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

Q: Most prokaryotic genomes are double-stranded circular DNA.

Q: 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.

Q: Each adenine-thymine base pair has ________ hydrogen bonds, while each guanine-cytosine base pair has ________ hydrogen bonds. A) two / one B) two / three C) four / three D) three / two

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

Q: 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

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

Q: 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.

Q: 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

Q: 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.

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

Q: 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

Q: 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.

Q: 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.

Q: Polycistronic transcription units are common in A) Archaea. B) Bacteria. C) Eukarya. D) both Archaea and Bacteria.

Q: 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.

Q: 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

Q: 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.

Q: 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

Q: 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.

Q: 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.

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

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

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

Q: Transcription of chaperonins 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.

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

Q: 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.

Q: Which of the following is NOT correct regarding DNA and RNA synthesis? A) The overall direction of chain growth is from the 5' to 3' 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.

Q: 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.

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

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

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

Q: 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.

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

Q: Transfer RNA 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.

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

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

Q: 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

Q: The template for RNA polymerase is ________, and the new RNA chain 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

Q: 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

Q: 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) 5'-phosphate / 3'-hydroxyl B) 3'-phosphate / 5'-hydroxyl C) 5'-deoxyribose / 3'-base D) 3'-base / 5'-deoxyribose