cDNA (complementary DNA) libraries are constructed using messenger RNA (mRNA) as the starting template rather than genomic DNA. mRNA represents the expressed portion of the genome. By using the enzyme reverse transcriptase, researchers synthesize a DNA strand complementary to the mRNA template. This process effectively captures the transcriptome of an organism at a specific developmental stage or under specific environmental conditions, allowing for the study of gene expression patterns.
14392
Which scientist is famously associated with the foundational work in genetic engineering and the deciphering of the genetic code?
Har Gobind Khorana (often spelled Koruna in some texts) played a pivotal role in genetic engineering by deciphering the genetic code. His work demonstrated how nucleotides in DNA specify the amino acids in proteins, which provided the essential framework for modern biotechnology and the manipulation of genetic material.
14393
What is the scientific term for the laboratory process of creating multiple identical copies of a specific gene sequence?
Gene cloning is a fundamental molecular biology technique used to isolate a specific DNA fragment and replicate it within a host organism. By inserting the target gene into a vector, such as a plasmid, and introducing it into a host cell like bacteria, the gene is replicated during the host's cell division, resulting in numerous identical copies of the genetic material.
14394
In what year were the foundational techniques for gene cloning first successfully developed?
The first successful recombinant DNA experiment, which demonstrated the ability to clone a gene, was performed by Herbert Boyer and Stanley Cohen in 1972. This breakthrough utilized restriction enzymes and DNA ligase to join DNA fragments from different sources, effectively launching the era of modern genetic engineering and biotechnology.
14395
Who were the researchers responsible for the discovery of transduction in viruses?
Norton Zinder and Joshua Lederberg discovered transduction in 1952 while studying Salmonella typhimurium. Transduction is a horizontal gene transfer mechanism where bacteriophages (viruses that infect bacteria) accidentally package host bacterial DNA and transfer it to another bacterium during subsequent infection cycles. This process is a significant driver of genetic variation in bacterial populations.
14396
Which DNA polymerase used in PCR is characterized by its inherent proofreading activity?
Pfu DNA polymerase, derived from the hyperthermophilic archaeon Pyrococcus furiosus, possesses 3' to 5' exonuclease activity. This allows the enzyme to perform proofreading, correcting mismatched bases during DNA synthesis. In contrast, standard Taq polymerase lacks this activity, resulting in a higher error rate during PCR amplification compared to Pfu.
14397
Which of the following is classified as an enzymatic method for DNA sequencing?
The Sanger method, also known as the chain-termination method, relies on the use of DNA polymerase to synthesize DNA strands in the presence of dideoxynucleotide triphosphates (ddNTPs). Because it utilizes an enzyme (DNA polymerase) to incorporate nucleotides, it is categorized as an enzymatic sequencing technique. In contrast, the Maxam-Gilbert method is a chemical degradation sequencing technique.
14398
Which organism is most commonly used as a host for gene cloning in laboratory settings?
Escherichia coli (E. coli) is the most widely used host organism for gene cloning due to its well-understood genetics, rapid growth rate, and the availability of numerous specialized cloning vectors. It allows for efficient replication and expression of foreign DNA sequences.
14399
Which gene was the first to be identified and cloned as a plant toxin gene?
The Hm1 gene in maize was the first plant toxin-related gene to be cloned. This gene plays a critical role in providing race-specific resistance against the fungus Cochliobolus carbonum race 1. It functions by expressing the NADPH-dependent HC toxin reductase enzyme, which effectively inactivates the HC toxin—a cyclic tetrapeptide produced by the fungus to facilitate infection. This discovery was a landmark achievement in understanding plant-pathogen molecular interactions.
14400
Which of the following components is NOT typically found in the final mature mRNA transcript after the process of transcription?
The provided answer key identifies 'Exons' as the correct choice, which contradicts standard molecular biology where exons are the coding sequences retained in mature mRNA. Introns are the non-coding sequences removed during splicing. This question may contain a conceptual error regarding the definition of exons versus introns. Users should be aware that in standard biological processes, exons are the segments that are transcribed and translated into proteins, while introns are excised.
