Recent questions tagged molecular-biology

Description : Are chromosomes the only parts of bacteria that can be transformed?

Last Answer : Bacteria possess extrachromosomal loops of DNA called plasmids. Plasmids are small, self-replicating loops of DNA with about 10 to 50 genes. They are not essential for the survival of the ... process called curing, which can occur spontaneously or can be induced by certain environmental factors. 

Description : What is cosmid?

Last Answer : Genetically engineered vector containing phage and plasmid genetic elements which accepts inserts of larger length (average of 45 kb) than phage (15 kb) or plasmid (1-10 kb) derived vectors. The ... the vector DNA which is then amplified and maintained as a giant plasmid in the host cell. 

Description : What is the structural basis of activation of heterotrimeric G proteins?

Last Answer : Heterotrimeric G proteins are composed of α, β, and γ polypeptide chains. Usually, the α and γ chains are anchored to the inner leaflet of the plasma membrane by lipid anchors that ... possible physiological effects that depend on which G protein-coupled receptor(s) they become associated. 

Description : How do brain cells store memories?

Last Answer : The part of your brain responsible for processing memory is the hippocampus. It is believed that memories are formed at the level of individual nerve cells. The synapse is the point at which adjoining ... , a protein, promotes synaptic growth and can convert short term memory to long term memory. 

Description : Insulin possesses two polypeptide chains denoted A and B that are linked by disulfide bonds. Upon denaturation by reduction of the SH groups of insulin, followed by reoxidation, only 7% of the ... can these data be reconciled with the hypothesis that the amino acid sequence directs protein folding?

Last Answer : Insulin is synthesized as preproinsulin that is proteolytically processed in the β cells of the islets of Langerhans in the pancreas, to give proinsulin. After synthesis and folding, a section of the ... lacking the C peptide, lacks some of the information necessary to direct the folding process. 

Description : What is the controversy surrounding Bt corn and the monarch butterfly?

Last Answer : Bt corn was specifically engineered to control the European corn borer, which in 2003 caused an estimated $1 billion worth of damage to U.S. farmers. In 1999 a study was ... to increase the probability of female monarchs encountering milkweed plants that are uncontaminated with corn pollen. 

Description : How can drug resistance develop in microorganisms? 

Last Answer : The use of antibiotics over the last 60 years has led to the development of drugresistant strains of bacteria.These bacterial strains always existed in the microbial population, but they never needed ... of drug resistance due to the selective pressures exerted by the increased use of antibiotics. 

Description : The bacterial RNA polymerase inhibitors rifampicin and streptolydigin each bind to the same subunitof the enzyme, but their overall effect on the activity of the enzyme is different. Why is this so?

Last Answer : Each of these inhibitors binds exclusively to the β-subunit of RNA polymerase. This subunit is involved in both initiation and elongation of RNA chain growth. Rifampicin binds to the subunit in such ... on elongation. Streptolydigin, on the other hand, binds in a manner that blocks both activities. 

Description : How is the production of a tissue-specific protein restricted to a particular tissue when the gene is present in the nucleus of all cells?

Last Answer : Most of the control of tissue-specific gene expression occurs at the level of transcription; this is achieved with tissuespecific transcription factors. E.g., all the genes that are to be expressed in ... when bound by a transcription factor, called GATA-1, which is present only in erythroid cells. 

Description : How do we study what function(s) a particular gene has in a cell?

Last Answer : One of the most informative ways to investigate the function of a gene is to determine its effect in vivo, by artificially introducing DNA into the cells of an organism. Such DNA is ... . Transgenic organisms therefore provide models to explore gene function, gene control, and human diseases  

Description : What characteristics of DNA polymerase III make it an ideal enzyme for replicating the whole genome?

Last Answer : The key features of DNA polymerase III are its catalytic potency, its fidelity, and its processivity. It is able to catalyze the addition of ~103 bases per second, compared to only about 10 per ... to dissociate from the template strand after synthesis of short (tens of bases) stretches of DNA.  

Description : What features of the structure of mRNA enable its interaction with the 30S subunit? 

Last Answer : Toward the 5′ end of mRNA there is a region of ~20 nucleotides prior to the initiation codon AUG. This leader region contains a purine-rich sequence that is responsible for the interaction of ... , which also involves the binding of the appropriately charged methionyl-tRNA opposite the AUG codon.  

Description : The development of genetic engineering has raised various concerns, moral and scientific. What might some of these be?

Last Answer : In many bacteria, the plasmids used in recombinant studies contain the gene conferring resistance to antibiotics.It was feared, during early attempts to effect DNA transplantation, that bacteria would be ... set up to deal with the ethical and biological issues involved in genetic engineering.  

Description : What are introns, and how do they affect the processing of genetic information?

Last Answer : Introns, a feature of eukaryotic DNA, are intervening stretches of DNA lying between the exons. The exons represent message material that actually gets translated into protein, whereas the introns must ... RNA is part of a protein-RNA particle known as the small nuclear ribonucleoprotein particle. 

Description : Why is the concept of a single gene as the ultimate unit of inheritance inadequate to provide a unitary explanation for protein synthesis, recombination, and mutation?

Last Answer : The primary function of the gene is to code for a protein product. Sufficient DNA must be present to account for each of the amino acids making up the primary structure of the protein. It is ... . The recon, the unit involved in recombination, may be only slightly shorter than the full cistron. 

Description : Why does thymine replace uracil in DNA? 

Last Answer : First, some clarification. As you already know, the difference between RNA and DNA is the existence of a hydroxyl (-OH) group on the 2' carbon of the ribose sugar in the backbone. The removal ... thymine for uracil in DNA protects the DNA from attack and maintains the fidelity of DNA replication.  

Description : How DNA Repair can happen? 

Last Answer : A. DNA damage caused by ultraviolet light: 1. cyclobutane-type pyrimidine dimer is the major photoproduct formed 2. a second product, the 6-4 photoproduct, is formed in about 10 % of UV induced ... 2. Bloom's syndrome. 3. Cockayne's syndrome 4. Fanconi's anemia 5. Ataxia telangiectasia   

Description : How Genes can be exchanged between chromatids? 

Last Answer : When two homologous chromosomes physically exchange corresponding segments during prophase I of meiosis, geneticists call it crossing over. Recombinations occur at chiasmata during pachytene of meiosis-I. If just ... to cut between genes that are far apart than genes that are closer together.  

Description : What is Barr body Genes? 

Last Answer : Located inside the nuclear envelope, it is a densely staining object that is an inactivated X chromosome in female mammalian cells. Most Barr body genes are not expressed. They are reactivated in gonadal ... transcript, is an RNA; multiple copies of XIST attach to the X chromosome inactivating it.  

Description : How the DNA nanoarchitecturing works? 

Last Answer : DNA nanoarchitectures constructs that can be self-assembled from branched DNA molecules. Their components may be simple branched species or more complex structural motifs. Simple branched DNA junctions have been ... a map of the western hemisphere are examples of patterns generated by this method. 

Description : What is genetic engineering? 

Last Answer : Genetic engineering, also popularly known as molecular cloning or gene cloning, is the artificial recombination of nucleic acid molecules in a test tube; their insertion into a virus, bacterial plasmid ... research, especially cancer research. Food processing: Rennin (enzyme) in cheese aging.

Description : What is green fluorescent protein (GFP) ? 

Last Answer : Green fluorescent protein is a protein found in a luminescent jellyfish (Aquorea victoria) that lives in the cold waters of the northern Pacific. Bioluminescence is the production of light by living ... of proteins. There are a variety of green fluorescent proteins that can glow different colors. 

Description : What are the stages of mitosis? 

Last Answer : Mitosis involves the replication of DNA and its separation into two new daughter cells. while only four phases of mitosis are often listed. the entire process is actually comprised of six phases: ... division of cytoplasm, cell membranes, and organelles occur. In plants. a new cell wall forms. 

Description : How much DNA is in a typical human cell? 

Last Answer : If the DNA (deoxyribonucleic acid) molecules in a single human cell were stretched out and laid end to end they would measure approximately 6.5 feet (2 meters). The average human body contains 10 to ... cells from one human were unraveled, it would stretch to the sun and back more than 500 times. 

Description : What is self-catalytic RNAs? 

Last Answer : Ribozymes - The term "ribozyme" was originally suggested by Thomas R. Cech, Nobel Prize winning biochemist, who first discovered this class of RNA molecules. A ribozyme is an RNA molecule that ... is catalyzed by the 23S ribosomal RNA, a potential ribozyme, rather than ribosomal proteins.  

Description : How DNA-RNA hybridization occurs 

Last Answer : Both DNA and RNA are able to form hybrids in solution with other DNA or RNA molecules that have complementary base pairing. Double-stranded DNA can be "denatured" by heating to high temperature. If the resulting single- ... RNA pairs with T of the DNA, and U or the RNA pairs with A of the DNA.  

Description : What are the features of hnRNA? 

Last Answer : Heterogeneous nuclear RNA (hnRNA) - The primary precursor mRNA transcript made in the eukaryotic nucleus are called "hnRNA," an abbreviation for "heterogeneous nuclear RNA. Features are as follows: Introns: Since many eukaryotic ... C in hnRNA. Thus hnRNA and mRNA are sequences of A, G, C and U's. 

Description : How sex occurs in bacteria? 

Last Answer : The occurrence of sex in bacteria was first described by Joshua Lederberg and Edward Tatum in 1946 (Nature, volume 158, page 558), who were studying mixed cultures of E. coli strains with ... Tatum, "These experiments imply the occurrence of a sexual process in the bacterium Escherichia coli." 

Description : Do all molecules of DNA have the same amounts of nitrogenous bases?

Last Answer : The number and sequence of nitrogenous bases in the DNA molecule are key elements in variations that are found in chromosomes. Different organisms have different numbers of the four bases, and the sequence ... and thymine will always be the same, as will the percentage of cytosine and guanine. 

Description : Is a gene the same as a DNA molecule? 

Last Answer : Genes are the units of heredity. A gene is a segment or section of a DNA molecule. This segment of DNA provides a genetic code for the synthesis of proteins. The nucleic acid language of the ... . This is the molecular language that will ultimately specify an amino acid sequence in a protein. 

Description : What is an example of gene control? 

Last Answer : An elegant example of gene control in bacteria is the operon system. A cluster of genes that is responsible for synthesizing a particular protein is called an operon. This cluster of genes typically includes ... (meaning they are normally off ) or repressible (meaning they are normally on ). 

Description : What are the main causes of Mutation? 

Last Answer : Some mutations occur randomly and spontaneously during the process of mitosis or meiosis. Other mutations are caused by mutagenic agents, which are environmental or man-made factors that can increase the frequency ... . A few examples of carcinogens are asbestos, benzene, some food dyes, and PCBs.