MBIO 305 Exam 1
Microorganisms that have complicated nutritional requirements are
fastidious
Which of the following is NOT a sterilization method?
Pasteurization
Which of the following is found only in bacteria?
Peptidoglycan
Place the following events in the process of virus replication and the generation of a transducing particle in the correct order.
1. A bacteriophage attaches to a specific receptor on a host cell 2. Phage DNA enters the bacterial cell. The empty phage coat remains outside the host cell 3. Enzymes coded for by the phage cut the bacterial DNA into small pieces 4. Phage nucleic acid is replicated and coat proteins are synthesized 5. During Virus assembly, bacterial DNA can sometimes mistakenly be packaged in the protein coat, creating a transfusing particle.
Which of the following statements regarding bacterial genetics is/are TRUE?
A change in genotype can change the phenotype. An auxotroph has a different genotype than a prototroph. An auxotroph has a different phenotype than a prototroph.
Which of the following statements about translation are CORRECT?
A codon can code for "punctuation"—for example, where translation should start or stop. Two different codons can code for the same amino acid. A codon is found on mRNA while an anticodon is found on the tRNA.
From which of the following would you be most likely to obtain a pure culture?
A single colony on a streak plate.
If the codon GGU is positioned in the A site of the ribosome, which of the following will occur?
A tRNA with the anticodon CCA will deliver its amino acid to the site. Correct
Match the important points regarding selection of an appropriate germicide with the description/rationale that fits it best.
Activity in the presence of organic matter:Some germicides may become less efficient when used in/on areas with organic matter. Storage and stability:Some germicides may lose efficiency over time, or may be required in very large amounts that would make them impractical for frequent applications. Toxicity:All germicides are somewhat harmful to humans and the environment. This parameter identifies HOW harmful the chemical is. Compatibility with the material being treated:Some substances are negatively affected by treatment with some germicides (i.e. corrosives damaging metals/rubber). Cost and availability:Some germicides are highly effective, but are rare and/or expensive.
Which of the following involves genetically modifying bacteria to produce compounds useful to humans?
Biotechnology
Match the mutation with the correct name. Not all labels are used.
C to G: silent Mutation G to C Missense mutation A to T: Nonsense mutation
_____ are groups of three bases in mRNA that specify one amino acid in the amino acid chain.
Codons
Match the term to its description to test your understanding of the use of moist heat to control microbial growth
Commercial Canning: Uses an autoclave called a retort to destroy the endospores of Clostridium botulinum. It will not destroy the endospores of some thermophiles. Steam under Pressure: Requires use of an autoclave. To sterilize, temperature must reach 121°C for a minimum of 15 minutes. Pasteurization: Heat applied to beverages to prevent spoilage and kill pathogens. High-temperature-short-time protocols include holding liquids at 72°C for 15 sec. Does not sterilize.
Which of the following shows the direction genetic information flows?
DNA → RNA → protein
Please match the term with its description to test your understanding of microbial control terminology.
Disinfection: Reduction of most microbial life on inanimate surfaces Sterilization: Destruction of all microbial life Preservation: Slows microbial growth but does not reduce the number of existing microbes. Decontamination: Mechanical removal of most microbes from living or inanimate surfaces
Which of the following is found exclusively in prokaryotic cells?
Endospore
Select the TRUE statement regarding eukaryotes
Eukaryotes have a more complex internal structure than archaea or bacteria AND have a membrane around the DNA.
Aldehydes can be used to disinfect superficial wounds.
False
Which of the following statements regarding bacterial gene control is FALSE?
Genes for constitutive enzymes can be turned on and off as necessary.
Which of the following are found exclusively in eukaryotic cells? Check all that apply.
Golgi apparatus, lysosomes, mitochondria, ER
Which of the following about heat treatment is FALSE?
It produces toxic byproducts.
During which phase of growth do researchers measure the generation time of a culture of bacteria?
Log phase
Match the statement to the term that it most accurately describes to test your understanding of theelements of good microscopy.
Magnification: The apparent increase in size of an image. Contrast:Ability to be distinguished from the surroundings. Resolution: The ability to distinguish between two separate structures that are very close to one another.
Using the genetic code (below), determine what type of mutation would occur if the last nucleotide in the codon AGA was converted to a U.
Missense
Which of the following statements about bacteria is FALSE?
Most bacteria have been grown in culture and characterized.
Identify all the statements that describe the benefits of microbes from a human perspective.
Nitrogen gas is not accessible for use by most organisms without the help of some microbes. Today's environmental oxygen levels may be a direct result of photosynthetic microbes. Microbes degrade/recycle metabolic wastes from other living organisms.
On one of the strands of bacterial DNA, the new complementary strand is synthesized discontinuously in small pieces of DNA called ______.
Okazaki fragments Correct
The initial transfer RNA occupies the _____ site on the ribosome.
P site
What usually terminates the process of translation?
Presence of a stop codon on mRNA
Please categorize the following words/ phrases as pertaining to either prokaryotes or eukaryotes by placing the words/statements in the appropriate column.
Prokaryotes: Nucleoid, single celled, bacteria, binary fission, peptidoglycan Eukaryotes: Membrane bound nucleus, single celled multicellular, protozoa, microscopic or macroscopic, mitosis
Which of the following types of repair does not require the standard DNA polymerase with proofreading capability?
SOS repair
Match the staining technique to the appropriate example.
Simple Stain: Single dye staining (example: Methylene blue stain) Differential Strain: Gram stain Special Strain: Endospore stain
When studying microbes, why is it important to separate mixed communities into individual pure cultures of the different species?
So we can understand the biochemical characteristics of one species without confusing it with another species.
If an organism lost the ability to make primase, what would it be unable to do?
Synthesize a short sequence of complementary RNA to the existing DNA strand.
Which of these is base-paired correctly?
T - A
In direct selection methods used to identify possible carcinogens (example: Ames testing), what does it mean when a chemical can cause a bacterium to develop resistance to some environmental condition?
The chemical is a mutagen.
Consider the figure and check the CORRECT statements.
The nucleobase shown in yellow should be a C. The CH3 groups alert the mismatch repair system to which DNA strand is the template strand. Without the CH3 groups, it is possible that the mismatch repair system would replace the G nucleobase (purple arrow) with an A.
Which of the following describes stationary phase of a growth curve?
The number of cells dividing equals the number dying.
Why is translation needed?
The subunits of nucleic acids are nucleotides, while those of proteins are amino acids
Match the following key terms to refresh yourself with the concepts of Chapter 8: Bacterial Genetics.
Transduction:mechanism of horizontal gene transfer in which bacterial DNA is transferred inside a phage coat Plasmid: an extrachromosomal DNA molecule that replicates independently of the chromosome Genotype: the sequence of nucleotides in an organisms DNA Auxotroph: a microorganism that requires an organic growth factor Wild Type: form of the cell or gene as it typically occurs in nature Phenotype: the observed characteristic of a cell Homologous Recombination: process by which a cell replaces a stretch of DNA with a segment of similar DNA sequences Transposon: segment of dan that can move from one genetic site to another within the genome Non Homologous Recombination: DNA recombination that does not require nucleotide sequence similarly Conjugation: a mechanism for horizontal gene transfer in which both cells become physically connected Horizontal Gene transfer: DNA transfer from one bacterium to another by conjugation, transformation, transduction Mutation: a change in the nucleotide sequence of a cells DNA that can be passed to its offspring Prototroph: a microorganism that does not requires an organic growth factors DNA mediated Transformation: mechanism of horizontal gene transfer in which the DNA is transferred as "naked" DNA
As hydrogen ions (protons) move across the bacterial cytoplasmic membrane along the electrochemical gradient, energy is harvested and used to drive ATP synthesis.
True
If you know the sequence of nucleotides in mRNA, you can deduce the DNA sequence it was transcribed from.
True
Pili that are used for attachment are also called fimbriae.
True
Replication, transcription and translation take place in the bacterial cytoplasm.
True
Compare and contrast the characteristics of viruses, viroids, and prions by placing the statements into the appropriate columns.
Viruses: DNA or RNA genome, Certain members can infect plants, animals, and even bacteria, Composed of nucleic acids surrounded by protein (lipid coating) Viroids: RNA genome only, members can only infect plants, composed of naked RNA only Prions: No genome (protein based), members can only infect certain animals, composed of only protein
In the absence of lactose, the lac repressor is
active and can bind to the operator.
The two strands of the DNA molecule are ______.
antiparallel
High concentration of salt and sugar in foods
are useful in preserving the food AND tend to draw water out of a cell.
Which of the following statements about bacteria is FALSE?
as a group, bacteria are very well characterized
The most common organisms causing food spoilage are
bacteria, yeasts, and molds.
A newly synthesized protein that contains a signal sequence will likely
be secreted from the cell that made it
DNA polymerase
can only add nucleotides in a certain direction.
Horizontal gene transfer can occur via
conjugation.
Moist heat kills microorganisms by
denaturing their proteins (causes proteins and enzymes to lose their three-dimensional functional shape). It also may melt lipids in cytoplasmic membranes.
Chlorine has traditionally been used to disinfect water, preventing the spread of waterborne illnesses. However, chlorine (and other disinfectants) can react with naturally occurring water chemicals, forming ______, which can have long-term health risks.
disinfection by products (DBP)
One bacterial chromosome replicates to become two chromosomes with
each made of one strand of DNA from the original chromosome and one newly synthesized strand.
Which of the following does not require energy?
facilitated diffusion
Which of the following bacterial structures is most directly linked to chemotaxis?
flagella
Production of extracellular polymeric substances (EPS) is necessary for bacteria to
form biofilms.
A culture of E. coli is irradiated with UV light. The UV light affects the cell's DNA by
forming covalent bonds between thymine bases on the same strand of DNA.
A segment of DNA encoding a protein or an RNA molecule is a ______.
gene
The lac operon is expressed when
glucose is low and lactose is present.
Early in the process of DNA replication, the enzyme ______ separates the two strands.
helicase
The two strands of DNA are joined to each other or held together by
hydrogen bonding
Which of the following kills food microbes, rather than just reducing their growth?
irradiation
Which of the following are considered the major elements that primarily make up components of cells in microorganisms and all living things?
nitrogen, phosphorus, sulfur, carbon, oxygen, hydrogen, potassium, magnesium, calcium, iron
Which of the following conditions would typically trigger sporulation for bacteria?
nutrient depletion
An enclosed compartment filled with an inert gas such as nitrogen would be most appropriate for growing ______.
obligate anaerobes
The specific point on the DNA molecule where replication begins is the
origin of replication.
The bond connecting amino acids is a ______ bond.
peptide
A ______ is the physical expression of the genes present and can change depending upon what genes are turned "on".
phenotype
The three basic parts of a DNA nucleotide are
phosphate, deoxyribose sugar, nitrogenous base. Correct
Haemophilus influenzae is a Gram-negative coccobacillus. If you looked at a Gram-stained culture using a light microscope, you would expect to see
pink, short rods
Choose which of the following results Pasteur might have obtained if the broth in his swan-necked flask experiment had contained endospores.
the broth would seem sterile after boiling but would soon develop bacterial growth
DNA polymerase
requires a template for the synthesis of DNA.
Protein synthesis occurs on the ______.
ribosomes
The target of penicillin in bacterial cells is ______.
the cell wall
Two different mechanisms for copying the DNA strands are used because
the strands are oriented in opposite directions.
Translation is needed because
the subunits of DNA and RNA are nucleotides while those of protein are amino acids
The mechanism by which genes are transferred into bacteria via viruses is called
transduction
The portions of bacteria that are involved in the movement of small molecules into the cells are called
transport proteins, permeases AND carriers
Microbes will only grow until the least represented (limiting) nutrient is used up.
true