Microbiology: Module 4

A long circular chromosome fits into a small E. coli cell

- by supercoiling - by using nucleoid associated proteins for packing -by the DNA double helix twisting on itself like a wound-up rubber band

Which of the following statements about a point mutation is FALSE?

- it may be a change to a different nucleotide. -it affects a base pair. - it may be a substituted nucleotide.

Genetic changes help modern bacteria in all of the following ways except -bacteria multiply rapidly allowing for genetic changes to appear quickly. -bacteria have been the recipients of genetic engineering. -bacteria can thrive everywhere. - large numbers of bacteria limit the potential for mutation.

- large numbers of bacteria limit the potential for mutation.

All of the following are genetically engineered solutions in use in the United States EXCEPT? -produce tomatoes that are less susceptible to viruses - produce insulin synthetically -produce more milk in dairy cows -all of the above

-All of the above

All of the following are part of an operon EXCEPT? -Promoter -Structural genes -Operator -Regulatory genes

-Regulatory genes

The genetic information carried on a plasmid can be used for

-antibiotic resistance. - bacteriocin synthesis. - transfer of genetic material.

Which of the following is not necessary for the process of DNA replication. -Okazaki fragments. -DNA polymerase. -DNA ligase -mRNA

-mRNA

Which of the following statements about DNA probes is false? -they are segments of RNA. -they can be used for medical diagnoses. - they may bind to the DNA of a host cell's chromosome. - they may contain a radioactive compound

-they are segments of RNA.

The mRNA that codes for a particular protein will have ___ nucleotides for each amino acid in the protein.

3

Which of the following is TRUE concerning the structure and function of enzymes? -Enzymes can function at a wide range of pH. -After an enzyme has catalyzed a reaction, it resumes its original shape and can interact with a new substrate molecule. -An apoenzyme is a combination of a cofactor bound to a holoenzyme. -Competitive inhibition of an enzyme occurs when an inhibitor binds to an allosteric site on the enzyme. -All enzymes bind cofactors necessary for their function.

After an enzyme has catalyzed a reaction, it resumes its original shape and can interact with a new substrate molecule.

To transfer a gene into plants, transposons isolated from which bacteria are used?

Agrobacterium.

What did the doctor mean when he referred to the HCV genotype causing Ingrid's infection, and why would identifying the genotype be helpful?

By referring to the HCV genotype that caused Ingrid's infection, the doctor meant that the genes that cause HCV were transferred to Ingrid through replication, transcription and translation when using the needle while getting her tattoo. This occurred through the process of transduction. It is important to determine the particular genotype to determine which medicine is going to treat the virus.

Organisms that require organic sources of carbon and energy are called _______.

Chemoheterotrophs

A cell that is capable of accepting DNA from the environment is called ___________.

Competent

involves F+ cells are donor cells.

Conjugation

involves a transfer of genes during a period of direct contact.

Conjugation

involves plasmids moving between live bacteria.

Conjugation

requires direct contact between donor and recipient cells.

Conjugation

The enzyme that seals DNA fragments together is called _______________.

DNA ligase

_________ is a useful tool in biotechnology that is a small slide surface on which genes or DNA segments are attached and arranged spatially in a known pattern that can be used to assess gene expression in microorganisms.

DNA microarrays

Experiments in genetic engineering are limited to transfer of DNA fragments between bacteria of the same genus and species.

False

Initiation of messenger RNA (mRNA) transcription requires a primer, which is provided by a promoter.

False

Prokaryote genome studies have shown that genes involved with the same process are spread out throughout the genome. This makes genetic control more efficient since their activity can be easily coordinated with each other.

False

Spectrophotometry is a direct method of determining the number of cells in a sample.

False

Sticky-end fragments generated by EcoRI will hydrogen bond to any other sticky-end sequence.

False

The central dogma states that DNA replication is semiconservative.

False

There are two origins of replication in every bacterial DNA molecule.

False

Transformations are generally more common than conjugations because DNA passes easily through the recipient cell's wall and membrane.

False

Under ideal conditions, the number of DNA molecules produced during PCR increases linearly.

False

You are a dog loving scientist who wants to insert into your dog a gene that encodes a protein that protects dogs from heartworms. A dog's cells are not competent, so they cannot take up the gene from the environment, but you know the heartworm resistant gene sequence, have a plasmid, a competent bacterium, and a related (though incompetent) F+ bacterium that lives as an intracellular parasite in dogs. Describe a possible scenario by which you could use natural processes to genetically alter your dog to be heartworm resistant.

First the genes needs to be inserted into a plasmid. Then, the gene carrying plasmid needs to be mixed with "competent" bacteria so these bacteria through transformation will pick the plasmid up. Then, the transformed bacteria should be cultured with the F+ "incompetent" bacteria. Through conjugation, the F+ bacteria will acquire the plasmid (with the gene). Finally, the F+ bacteria carrying the plasmid (with the gene) will be inoculated into the dog.

The base sequence of a messenger RNA molecule that is complementary to the sequence CGTTAGA would be expressed as

GCAAUCU.

Explain how the genotype of a prokaryote determines its phenotype?

Genotype is the actual set of genes or an organism and those genes are what make up the phenotype or the physical characteristics and traits of that organism such as the structures morphology and metabolism. Genotypes specify certain phenotypes by determining what kinds of RNA and which structural, enzymatic, and regulatory protein molecules are produced. This is done through the central dogma of genetics where the DNA strand goes through transcription where a cell transcribes RNA through a DNA gene. mRNA then carries this information to the ribosomes as codons. Ribosomes then translate polypeptides using the code carried by RNA molecule. These polypeptides then determine the phenotype.

Metabolic activity of a microbe is at maximum level in the ________ phase of growth.

Log

Which codon would match to the tRNA anticodon TTT?

No such anticodon exists

Discuss one of the pros and cons regarding the application of recombinant DNA technology.

One of the largest advantages that I can see of recombinant DNA technology is that we can use specific genes that we know can have a positive affect on eliminating negative phenotypes. An example of this would be the ability to produce more insulin in your body for those that have a defective gene. While I do see many positives in recombinant DNA technology, one of the negatives could be the unexpected impact that a new gene might have on the body when combined with the current gene. For example, in gene therapy a "good" gene replaces a historically negative gene for a particular medical condition, however, we have seen many unexpected side effects that have slowed the advancements in this area.

____________ is a technique that takes a segment of DNA and replicates it millions of times in just a few hours.

Polymerase chain reaction

The PCR process commonly uses DNA polymerase isolated from T. aquaticus bacteria. Explain why can't DNA polymerase isolated from E. coli be used instead.

Polymerase chain reaction is the process of enzymatically replicating a large scale of DNA without using living cells which allows scientists and researchers to do things such as detecting hereditary diseases, determining "genetic fingerprints" and analyzing relationships among different cells. The process of polymerase chain reaction is quite simple and involves a three step process: heating the cell at 94 degrees (C) in order to break the hydrogen bonds on DNA and unzip the double helix for replication. Unfortunately this hot temperature denatures most DNA polymerase enzymes those isolated from E.coli. E. coli does not thrive in hot temperatures and is killed when heated appropriately. T. aquaticus bacteria, however, is a bacterium that thrives in hot springs and therefore can survive the heat and move forward with the replication, transcription and translation process.

Detection of a pathogen by PCR requires the use of a set of unique sequence _________.

Primers

Transcription acts to

Produce RNA molecules

involves DNA polymerase activity.

Replication

produces Okazaki fragments

Replication

requires DNA ligase to seal DNA fragments.

Replication

Describe three ways scientists use synthetic nucleic acids

Scientists use synthetic nucleic acids in several ways. The first is by elucidating, or identifying, genetic code by using certain synthetic nucleic acids to understand the amino acid sequence of proteins that will follow. Once the genetic code is identified, we can then create genes for specific proteins that can be used for positive medical advancements, such as the gene for insulin. Finally, synthetic nucleic acids also allow us to create DNA or RNA probes that have a fluorescent chemical or radioactive element that will allow us to identify complimentary nucleotide sequences that researchers can use in genetic engineering.

Changes in temperature or pH can cause enzymes to lose activity. What is a common feature of these two effects?

Temperature and pH both induce an enzyme to lose its precise three-dimensional shape.

Variations in viral genotypes are the result of mutations, which are permanent changes in the genome. Describe the major types of mutations that occur to produce varying genotypes.

The major types of mutations are point mutations and gross mutations. Point mutations are most common and where a single nucleotide base pair is affected such as substitutions, insertion or deletions (frame shift mutations). Point mutations include silent mutations which do not alter the amino acid, missense mutations where a change specifies a different amino acid and nonsense mutations where a change puts a stop codon in place of an amino acid. The final type of mutation is a gross mutation which is where there is inversion, duplication, or transpositions

A wild-type organism and a genetic variant both have a gene encoding a receptor producing a chemotactic response to metabolite A. The genetic variant has a mutation in a regulatory gene for expression of the receptor. Which of the following statements with respect to the receptor is CORRECT?

The organisms have the same receptor genotype but different phenotypes.

What is a risk of using a retrovirus as a vector for gene therapy?

The retrovirus could insert its DNA copy into a gene rather than next to genes. This would cause the loss of genetic information. The result could be a mutation or even cell death.

All of the following describe F plasmids EXCEPT: -They are a double-stranded loop of DNA. -They carry genes for essential bacterial metabolism. -They are found in F+ cells. -They contain genes for production of the pilus

They carry genes for essential bacterial metabolism.

is a DNA-dependent RNA synthesis process.

Transcription

requires a promoter sequence.

Transcription

carries viral genes from bacterial chromosomes.

Transduction

includes the attachment of viral DNA to the bacterial chromosome.

Transduction

occurs when naked pieces of DNA are taken up from the environment.

Transformation

requires that competent cells be available.

Transformation

begins with a start codon.

Translation

involves a transfer of amino acids to an elongating chain.

Translation

involves releasing factors.

Translation

Cell contact is necessary for bacterial conjugation to occur but does not occur for transduction.

True

In semiconservative DNA replication, a new strand of DNA with bases complementary to a parent strand combines with a parent strand to form the double helix.

True

Many antibiotics affect protein synthesis in bacterial cells and therefore are clinically useful in treating human infections and disease.

True

The ability to utilize different metabolites for cellular respiration is one method for identifying bacteria.

True

Which of the following is an example of a frameshift mutation when the original DNA molecule is ATA CGC GGG TAC GTA? (The responses are in mRNA language).

UAU GCG CCA UGC AU

What is an advantage for choosing a disabled form of retrovirus as a vector for gene therapy?

With the virus crippled, retroviral disease is less likely to develop in the person treated by gene therapy.

Recombinant DNA technology can be most accurately defined as the

deliberate modification of the genome of an organism for practical purposes.

Organisms that can grow with or without oxygen present are

either facultative anaerobes or aerotolerant anaerobes.

The northern blot is a technique used to detect specific RNA molecules in a larger population of molecules that have been separated by ____________.

gel electrophoresis

An epidemiologist is investigating a new disease and observes what appear to be bacteria inside tissue cells in clinical samples from victims. The scientist wants to try to isolate the bacteria in the lab. What culture conditions are most likely to be successful?

inoculation of cell cultures

The Ames test is used to

learn whether a chemical can induce a bacterial mutation.

A ______________ is a substance which induces changes in DNA bases.

mutagen

The procedure known as "replica plating" is used in

negative selection only.

An mRNA stop codon codes for

no amino acid

A(n) (genome/codon/operon) is a set of prokaryotic genes that are regulated and transcribed as a unit.

operon

A ________________ is a closed circular piece of DNA that contains few genes which are non-essential to the cell.

plasmid

In gel electrophoresis, DNA molecules move toward the ________ electrode(s) because they have an overall ________ charge.

positive; negative

If a donor E. coli cell transfers DNA to a recipient Shigella cell what could happen?

possible transfer of antibiotic resistance

A plasmid was produced through genetic engineering that contains a gene for human insulin. Such a plasmid is called a(n)

recombinant plasmid.

Mutations arising from chance events in the environment are known as __________ mutations.

spontaneous

A bacterium's genome consists of

the complete set of genetic information.

The method of obtaining isolated colonies that utilizes surface area to physically dilute specimens is called:

the streak-plate technique.

Genes that are passed between parent and offspring is called

vertical gene transfer