Molecular Biology (Chapter 1-5, 20-23)

The correct statement is that colonies that contain recombinants are colorless due to the disruption of the lacZ gene by the insert. This is because the lacZ gene is responsible for producing an enzyme called beta-galactosidase, which is required for the breakdown of a colorless substrate called X-gal into a blue product. When the lacZ gene is disrupted by the insert, the colonies are unable to produce the enzyme and therefore do not turn blue.

The T7phage promoter is included in the construction of an expression vector to stimulate a high level of RNA synthesis. The T7phage promoter is a strong promoter that efficiently drives transcription in bacterial cells. It is commonly used in molecular biology research to produce large amounts of RNA transcripts for various applications. The other options listed, such as the origin of replication, Amp gene, His region, and GFP, are not directly involved in stimulating RNA synthesis.

Gel filtration is the most effective method for rapidly purifying proteins based on size. This technique separates proteins based on their molecular weight using a porous gel matrix. When a protein sample is applied to the gel, smaller proteins are able to enter the pores and travel through the gel more slowly, while larger proteins are excluded and elute first. As a result, the proteins are separated and can be collected in individual fractions. Gel filtration is advantageous because it does not require harsh conditions or denaturing agents, allowing for the preservation of protein structure and activity during purification.

TerE is not part of the E.coli primosome. The primosome is a complex of proteins that is involved in DNA replication. DnaA, DnaB, oriC, and DnaG are all components of the primosome. However, TerE is not involved in DNA replication and is unrelated to the primosome.

Correct answer is: (C) crossover events occur between homologous genes

The correct answers is: (C) Most tRNA molecules would not be able to attach to amino acids

Based on the information provided, the presence of at least 120 clear plaques indicates that the vector could be a phage. Phages are viruses that infect bacteria and can form clear plaques on a bacterial lawn. Plasmids, Ti plasmids, puc18, and cosmids are all types of vectors, but they do not typically form clear plaques. Therefore, the most plausible conclusion is that the vector is a phage.

In hybridization, DNA from two separate sources combine. This process involves the joining of two DNA molecules from different sources to form a hybrid molecule. This can be done in a laboratory setting by denaturing the DNA strands, allowing them to separate, and then reannealing them together. Hybridization is commonly used in molecular biology techniques such as DNA sequencing, DNA fingerprinting, and gene expression analysis.

RecA is the correct answer because it is known to coat the single stranded DNA tail produced by exonuclease activity in the E. coli RecBCD pathway. RecA plays a crucial role in homologous recombination by binding to the single stranded DNA and facilitating the strand invasion and exchange with the homologous DNA template. This allows for the repair of DNA damage and the formation of new genetic combinations.

Correct answer is: (B) phosphate-sugar-base

Correct answer is: (D) heat inactivation

not-available-via-ai

Correct answer: (A) McClintock and Creighton

Correct answer is: (B) a genetic trait can be transferred from one organsim to another

Using a prokaryotic expression system for eukaryotic proteins can lead to the proteins being improperly folded. Prokaryotic cells lack the machinery and post-translational modifications required for proper folding of eukaryotic proteins. As a result, the proteins may not adopt their correct three-dimensional structure and may be functionally inactive or unstable. This can affect their biological activity and overall usefulness in research or industrial applications.

When cloning eukaryotic DNA into prokaryotic cells, it is necessary to add DNA without introns. This is because prokaryotic cells lack the machinery to process and remove introns from mRNA. Therefore, if DNA with introns is used, the prokaryotic cells will not be able to correctly transcribe and translate the DNA into protein. By adding DNA without introns, the prokaryotic cells can efficiently express the genes of interest without any intron-related complications.

A primosome is a collection of proteins that are required for the synthesis of primers during the replication of DNA. Primers are short RNA sequences that serve as starting points for DNA replication. These proteins work together to unwind the DNA double helix, stabilize the unwound DNA, and recruit the enzyme responsible for primer synthesis. Therefore, the correct answer is "a collection of proteins needed for synthesis of primers for replicating DNA."

The statement that E.coli RecA protein is only necessary for the presynapsis step of homologous recombination is false. E.coli RecA protein is actually required for multiple steps in homologous recombination, including presynapsis, synapsis, and postsynapsis. It plays a crucial role in DNA strand exchange, promoting the pairing of homologous DNA molecules and facilitating the exchange of genetic material. Therefore, the correct answer is False.

Correct answer is: (E) both (A) and (B) are correct

Correct answer is: (D) genes are arranged in a linear order on chromosomes

The noncoding strand of a gene is not the same as the antisense strand. The noncoding strand is the template strand that is transcribed into RNA, while the antisense strand is the complementary strand to the coding (sense) strand.

The correct answer is: (B) Linn and Arber

Baculovirus is the best choice for the expression of eukaryotic proteins because it is a type of virus that infects insect cells and has been widely used as a vector for protein expression in eukaryotic systems. Baculovirus vectors offer high protein yields, proper post-translational modifications, and efficient protein folding, making them suitable for the production of complex eukaryotic proteins.

Southern blotting is a technique used for detecting specific DNA sequences, not for quantifying gene expression. It involves the transfer of DNA fragments from a gel to a membrane, which is then hybridized with a labeled probe. This technique is useful for determining the presence or absence of a specific DNA sequence, but it does not provide information about the level of gene expression. Other techniques like northern blotting, S1 mapping, RNase protection, and nuclear run-off are commonly used for quantifying gene expression.

Prokaryotic single stranded DNA binding proteins play a crucial role in cell replication by binding to and stabilizing single-stranded DNA (ssDNA) during DNA replication. They prevent the ssDNA from reannealing and aid in the action of helicase, which unwinds the DNA strands. Additionally, they stimulate DNA polymerase, which is responsible for synthesizing new DNA strands. Therefore, the statement "They are not essential for cell replication" is incorrect because these proteins are indeed essential for the process of DNA replication in prokaryotic cells.

UV radiation causes DNA damage by forming pyrimidine dimers. Pyrimidine dimers occur when two adjacent pyrimidine bases (thymine or cytosine) in the DNA molecule become covalently bonded, disrupting the normal structure of the DNA helix. This can lead to errors in DNA replication and transcription, potentially causing mutations and other genetic abnormalities. X-rays and gamma radiation can also cause DNA damage, but they do so through different mechanisms such as ionization. Alkylating agents and ethidium bromide can also cause DNA damage, but they do not specifically form pyrimidine dimers.

DNA gyrase is an enzyme that adds negative supercoils to DNA molecules, not positive supercoils. Supercoiling is the process of twisting the DNA molecule upon itself, and DNA gyrase is responsible for introducing negative supercoils by cutting and resealing the DNA strands. These negative supercoils help in the compaction and organization of DNA within the cell. Therefore, the given statement is false.

The correct answer: (C) the strands to remain separted. a common procedure to ensure that denatured DNA stays denatured is to brunge the hot dna solution into ice also called quenching.

The correct asnswer is: (D) the unit would dissociate from RNA and protein components

The statement is false because bacteria use the restriction-modification system to protect themselves from foreign DNA, not to synthesize new DNA molecules. This system involves the production of restriction enzymes that can recognize and cut specific DNA sequences, preventing the entry of foreign DNA into the bacterial cell. The modification enzymes then add methyl groups to the bacterial DNA, marking it as "self" and protecting it from being cut by the restriction enzymes. This system is a defense mechanism rather than a mechanism for DNA synthesis.

The correct answer is 1000nt/sec. This means that DNA polymerase III holoenzyme can synthesize 1000 nucleotides per second in vivo. This is a high rate of DNA synthesis, indicating the efficiency and speed of this enzyme in replicating DNA.

Correct answer is: (D) All A-C are correct

Correct answer is: (E) A, B and C

The correct answer is: (B) No label would be found in the RNA

The given sequence 5'-ACCGTAG- GATGCCA-3' is not an example of an inverted repeat sequence. Inverted repeat sequences are DNA sequences that read the same forward and backward on complementary strands. In this case, the sequence does not have a complementary sequence that reads the same in the opposite direction. Therefore, the correct answer is False.

Correct answer is: (B) Beadle and Tatum

Correct answer is: (B) Destruction by the host's white blood cells

cDNA, or complementary DNA, is synthesized from a messenger RNA (mRNA) template using the enzyme reverse transcriptase. It is a DNA molecule that contains only the exons, or coding regions, of a gene, without the introns, or non-coding regions. This allows for the production of a DNA molecule that is a complementary copy of the mRNA, which can then be cloned into prokaryotes for further study or manipulation. Therefore, the correct answer is "eukaryotic DNA with only exons that can be cloned into prokaryotes."

The most common type of DNA damage repair is excision repair. This process involves the removal of damaged or incorrect nucleotides from the DNA strand and replacing them with the correct ones. It is a highly efficient mechanism that helps maintain the integrity of the DNA molecule and prevent the accumulation of mutations. Excision repair is involved in repairing various types of DNA damage, including UV-induced pyrimidine dimers, chemical adducts, and other types of base modifications. This repair mechanism is essential for the cell's survival and plays a crucial role in maintaining genomic stability.

DNA gyrase is an enzyme that introduces negative supercoils in the DNA. Supercoiling is the twisting or coiling of the DNA molecule, and it can be either positive or negative. In the case of DNA gyrase, it introduces negative supercoils by breaking and rejoining the DNA strands, which helps in the compaction and organization of the DNA molecule. Positive supercoiling, on the other hand, is introduced by other enzymes such as topoisomerase I. Therefore, the correct answer is negative.

Barbara McClintock discovered the first eukaryotic transposable element in maize. This means that she found the first instance of a mobile genetic element that can change its position within the genome of a maize plant. This discovery was groundbreaking as it provided evidence for the existence of genetic elements that can move and potentially impact gene expression and genome evolution. McClintock's work in maize genetics revolutionized our understanding of genome dynamics and earned her the Nobel Prize in Physiology or Medicine in 1983.

Correct answer is: (B) Morgan

The correct answer is: (E) ribonuclease

Branch migration is not a spontaneous process that takes place after a Holliday junction is formed. Instead, branch migration is an enzymatic process that occurs during the resolution of a Holliday junction, where the DNA strands are moved along the junction to promote either crossover or non-crossover events. Therefore, the correct answer is False.

The Ds transposable element of maize cannot transpose on its own because it lacks transposase. Transposase is an enzyme that is required for the movement of transposable elements within a genome. Without transposase, the Ds element is unable to undergo transposition, which is the process of moving from one location to another within the genome. Therefore, the absence of transposase prevents the Ds element from transposing on its own.

The migration of polypeptides through the gel in SDS-PAGE is primarily determined by their size, as smaller molecules can move more easily through the pores of the gel. The strength of the electric field also affects the migration, as a stronger field will cause faster movement. The molecular mass of the protein is indirectly related to its size and can influence the migration. SDS (sodium dodecyl sulfate) is a detergent used in SDS-PAGE to denature proteins and give them a negative charge, which helps to separate them based on size. However, the native charge on the polypeptides does not directly affect their migration in SDS-PAGE, as SDS masks the native charge and provides a uniform negative charge to all proteins.

The (e)-subunit of DNA Polymerase III core enzyme does not function in proofreading by having 5'---->3' exonuclease activity. The correct answer is False.

When the UC18 plasmid DNA sample is treated with the BAMHI restriction enzyme, it cuts at the restriction sites located at position 100 and position 2000. This results in two fragments being produced: one fragment of size 1900 bp (from position 100 to position 2000) and another fragment of size 1100 bp (from position 2000 to position 100 and then back to position 100 again). Therefore, the correct answer is 1900,1100.

The statement that is not true concerning DNA replication in prokaryotes is "DNA replication requires only one enzyme". In reality, DNA replication in prokaryotes requires multiple enzymes, including DNA polymerase, primase, helicase, ligase, and topoisomerase. These enzymes work together to unwind the DNA double helix, synthesize new DNA strands, and seal any gaps in the newly synthesized DNA. Therefore, the statement that DNA replication requires only one enzyme is incorrect.

The statement is false because EcoRI and BamHI have different recognition sequences, so they would not produce compatible sticky ends. Therefore, a fragment restricted with EcoRI enzyme cannot be used for ligation into a plasmid restricted with BamHI.

The run-on transcription assay is a technique used to measure the transcription rates of genes. It involves using isolated nuclei, not including cytoplasmic RNA, and performing the reaction in the presence of labeled nucleotides. By analyzing the labeled RNA, the assay can identify the genes that are being actively transcribed. Therefore, the statement "Cytoplasmic RNA is included in the assay" is not true about the run-on transcription assay.

A report gene assay would be the best choice for this study because it allows researchers to measure the activity of the isolated insulin gene. The assay involves linking the insulin gene to a reporter gene, such as luciferase or green fluorescent protein, which produces a measurable signal when the insulin gene is active. This would provide valuable information about the function of the insulin gene and its regulatory elements. Southern analysis, immunoblotting, PCR, and immunoprecipitation are not suitable for directly studying the function of a gene.

The constant region of an antibody does not contain the antigen binding domains. The antigen binding domains are located in the variable region of the antibody. The constant region is responsible for mediating effector functions and determining the class and isotype of the antibody.

Correct answer is: (E) Mapping is used ot determine the compositon of a gene.

All of the choices are true. Since the recombinant plasmid contains an ampicillin resistance marker, all transformed bacteria, including both the transformed and untransformed ones, will be able to grow on a plate containing ampicillin. Additionally, the presence of multiple restriction enzyme sites in the plasmid makes it difficult to screen for a colony containing the plasmid. Therefore, it is true that it will be difficult to screen for a colony containing a plasmid. Lastly, it is recommended to use an ampicillin-sensitive bacterial host for screening purposes.

To generate rare restriction sites on the cDNA strands, one would use the technique of ligating cDNA to specific linkers. Linkers are short DNA sequences that contain rare restriction sites. By ligating these linkers to the cDNA strands, rare restriction sites can be introduced. This allows for the identification and isolation of specific DNA fragments within the cDNA library using the corresponding restriction enzymes. Restriction enzymes, PCR with multiple cycles, and BamHI restriction followed by ligation are not methods specifically used to generate rare restriction sites on the cDNA strands.

DNase-1 footprinting is used to study the interaction of proteins with DNA. This technique involves the digestion of DNA with DNase-1, which cleaves DNA at specific sites. However, when a protein is bound to the DNA, it protects the DNA from digestion, resulting in the formation of a "footprint" or region of DNA that is not cleaved by DNase-1. By analyzing the pattern of DNA cleavage, researchers can determine the location and strength of protein-DNA interactions. S1 nuclease protection, DNA fingerprinting, southern analysis, and northern blotting are all techniques used for different purposes and are not specifically used to study protein-DNA interactions.

Spectrophotometry is a method used to measure the absorption or transmission of light by a substance. It is commonly used to determine the concentration of a substance in a solution. However, spectrophotometry does not have the ability to detect radioactivity directly. On the other hand, the other methods listed (liquid scintillation counter, autoradiography, x-ray film, and phosphorimaging) are all commonly used techniques to detect and measure radioactivity in biological samples.

Site-directed mutagenesis is a technique used to make specific changes to the bases in DNA. This can involve introducing mutations, deletions, or insertions at specific locations in the DNA sequence. It allows researchers to study the effects of specific changes on gene function and protein structure. The other options mentioned, such as inserting fragments, inducing site-specific recombination, and removing large segments of DNA, are not the primary purposes of site-directed mutagenesis.

The correct answer is square planar conformation. Molecular modeling studies have shown that RuvA and a Holliday junction form a square planar conformation, which allows for rapid branch migration. This conformation provides the necessary flexibility and stability for the efficient movement of the DNA strands during genetic recombination.

During meiosis in N. crassa, gene conversion can occur through mismatch repair. Mismatch repair is a mechanism that corrects errors in DNA replication by identifying and removing mispaired bases. In the context of gene conversion, mismatch repair can be triggered when a heteroduplex is formed during recombination. If there is a mismatch between the two DNA strands in the heteroduplex, the mismatch repair machinery can recognize and repair the mismatch by either replacing the incorrect base with the correct one or by initiating DNA synthesis to correct the mismatch. This process can result in the conversion of one allele to another, leading to genetic diversity.

All of the techniques mentioned (EMSA, DNase footprinting, filter binding, and gel mobility shift assay) can be used to confirm the suspicion that a novel histone protein only interacts with the promoter region of B-globin genes. EMSA (Electrophoretic Mobility Shift Assay) can determine if the protein binds to the DNA sequence, DNase footprinting can identify the specific binding site, filter binding can quantify the binding affinity, and gel mobility shift assay can confirm the interaction between the protein and the DNA. Therefore, all of these techniques are appropriate for confirming the suspicion.

The statement is false because the recombinases RAG-1 and RAG-2 are not expressed in plasma and memory B-cells. These recombinases are actually expressed in developing B and T cells during the process of V(D)J recombination, which is crucial for generating diverse antigen receptors. Once B cells undergo this recombination process and mature into plasma or memory B cells, RAG-1 and RAG-2 expression is turned off.

DNA Pol (&) is not correctly matched with its function of ligation of DNA strands. DNA Pol (&) is actually involved in the process of nucleotide excision repair, which is a DNA repair mechanism.

DNA gyrase is a type of topoisomerase II enzyme that is responsible for alleviating supercoiling in DNA. Supercoiling occurs when the DNA helix becomes twisted and can interfere with various cellular processes. To unwind the supercoiled DNA, DNA gyrase uses the energy from ATP hydrolysis. ATP provides the necessary energy for DNA gyrase to break and rejoin DNA strands, allowing for the release of supercoiling and the maintenance of DNA structure and function.

During retroviral replication, reverse transcriptase uses a host tRNA molecule as a primer. Reverse transcriptase is an enzyme that synthesizes DNA from an RNA template, and it requires a primer to initiate the synthesis. In this case, the host tRNA molecule serves as the primer, providing the necessary starting point for reverse transcriptase to begin synthesizing viral DNA. The other molecules listed, such as host snRNA, viral RNA, viral DNA, and host DNA, do not serve as primers during retroviral replication.

Electron microscopy was key in demonstrating the presynapsis and synapsis steps of homologous recombination because it allows for high-resolution imaging of biological samples, including DNA molecules. This technique enables researchers to visualize the physical interactions between DNA strands during the process of homologous recombination, providing valuable insights into the mechanisms and steps involved.

West and colleagues used gel mobility shift assays to demonstrate that RuvC could bind to and resolve Holliday junctions.

Recombinant repair is not an actual repair mechanism, but rather a damage bypass mechanism. It involves the exchange of genetic material between two DNA molecules, which can lead to the formation of new combinations of genes. This process does not directly repair the damage in the DNA, but rather allows for genetic diversity and adaptation in organisms.

Tn3 is the correct answer because it is a transposon, a type of DNA sequence that can move from one location to another within a genome. Transposons do not have a reverse transcriptase gene associated with them. In contrast, HIV, Ty, AMV, and L1 are all retroviruses or retrotransposons, which have a reverse transcriptase gene that allows them to convert their RNA genome into DNA for integration into the host genome. Therefore, Tn3 is the only option that does not have a reverse transcriptase gene.

DnaG is the correct answer because it is the primase that synthesizes RNA primers during DNA replication in E.Coli. Primers are necessary for DNA polymerase to start replication, and DnaG is responsible for synthesizing these primers by adding RNA nucleotides to the DNA template. DnaG is an essential component of the replication machinery and plays a crucial role in initiating DNA replication.

The Tn3 transposon is a type of mobile genetic element that can move from one location to another within a genome. It typically contains inverted repeat sequences, antibiotic resistance genes, resolvase genes, and transposase genes. The oriT site, on the other hand, is a site that is involved in the initiation of DNA transfer during conjugation, which is a different mechanism of genetic transfer. Therefore, it is not likely to be a characteristic of the Tn3 transposon.