Practice Questions_dr. Schlegel_may_aug2011 _pt.2

RNA polymerase initiates transcription by recognizing specific nucleotide sequences called promoters. Promoters are regions of DNA that signal the starting point for transcription. They provide binding sites for RNA polymerase and other transcription factors, allowing the initiation of transcription and the synthesis of RNA from the DNA template strand.

Transposons are "jumping genes" that have the ability to move from one location to another within an organism's genome. They are also known as transposable elements and can cause genetic changes by inserting themselves into different positions in the DNA sequence. This mobility allows transposons to play a role in evolution and can have both positive and negative effects on an organism's phenotype.

The SOS response is a DNA repair mechanism that is activated in response to extreme DNA damage. When the DNA is severely damaged, the SOS response is triggered to prevent further damage and promote DNA repair. This response involves the upregulation of various genes involved in DNA repair and replication, as well as the activation of error-prone DNA polymerases that can introduce mutations in order to bypass the damaged DNA. Overall, the SOS response is an important mechanism to ensure the survival of cells under conditions of extreme DNA damage.

Generalized transduction is a type of horizontal gene transfer where viruses, called bacteriophages, carry random fragments of host DNA from one bacterial cell to another. This occurs when a bacteriophage mistakenly packages host DNA instead of its own DNA during the viral replication process. As a result, when the virus infects another bacterial cell, it transfers this random DNA sequence, which can then be incorporated into the recipient cell's genome. Therefore, the statement that in generalized transduction, viruses carry random DNA sequences from one cell to another is true.

The leading strand is the DNA strand that is synthesized continuously during DNA replication. This is because the leading strand is oriented in the 3' to 5' direction, which allows DNA polymerase to add nucleotides in a continuous manner. In contrast, the lagging strand is oriented in the opposite direction (5' to 3') and requires the synthesis of short Okazaki fragments that are later joined together. Therefore, the leading strand is the correct answer as it is the strand that is synthesized continuously during DNA replication.

The replication fork/bubble is the point at which a DNA double helix is "unzipped" during the process of DNA replication. This is where the two strands of the DNA molecule separate and serve as templates for the synthesis of new complementary strands. The replication fork/bubble is formed by the action of enzymes called helicases, which unwind the DNA helix and create a Y-shaped structure. The replication fork/bubble is a crucial site for DNA replication as it allows for the simultaneous synthesis of both leading and lagging strands.

A gene is a specific sequence of nucleotides that codes for a protein or an RNA molecule. It is the fundamental unit of heredity and carries the instructions for the synthesis of proteins, which are essential for the functioning and development of organisms. Genes are located on chromosomes and are responsible for the transmission of traits from parents to offspring. They play a crucial role in determining an individual's characteristics and are involved in various biological processes.

The anticodon of a transfer RNA molecule is complementary to a codon in a messenger RNA molecule. The anticodon is a sequence of three nucleotides located on the tRNA molecule that specifically recognizes and binds to the corresponding codon on the mRNA during protein synthesis. This complementary base pairing between the anticodon and codon ensures that the correct amino acid is added to the growing polypeptide chain.

During translation, the growing polypeptide is positioned in the P site of the ribosome. The P site, also known as the peptidyl site, is one of the three binding sites on the ribosome where tRNA molecules are held during protein synthesis. The P site specifically holds the tRNA molecule carrying the growing polypeptide chain, allowing for the addition of new amino acids to the chain.

dATP and dCTP are examples of triphosphate deoxyribonucleotides, which are the building blocks of DNA molecules. These molecules are essential for DNA replication and synthesis, as they provide the necessary nucleotides to form the DNA chain. The "tri-" in triphosphate indicates that these molecules have three phosphate groups attached to the sugar backbone, providing energy for the DNA synthesis process. Deoxyribonucleotides refer to the type of sugar present in the molecule, which is deoxyribose. Therefore, dATP and dCTP are specific examples of triphosphate deoxyribonucleotides that contribute to the formation of DNA molecules.

Cells that are able to perform transformation are referred to as "competent". This term is commonly used in molecular biology to describe cells that have been treated or engineered to take up foreign DNA molecules and incorporate them into their own genetic material. Competent cells have enhanced abilities to uptake and express exogenous DNA, making them useful tools in genetic engineering and biotechnology applications.

The organization of the genes targeted by this quorum-sensing system is best described as a regulon. A regulon refers to a set of genes or operons that are controlled by a common regulatory protein or mechanism. In this case, the binding of the autoinducer peptide to the sensor kinase leads to altered regulation of genetic loci present on different parts of the chromosome and transcribed in different directions. This suggests that the quorum-sensing system is coordinating the expression of multiple genes or operons, which is characteristic of a regulon.

The product of micF is a nucleic acid, so the most likely way it would bind to mRNA would be by sequence complementarity. The fact that it binds mRNA means that it is working AFTER transcription. Of the options presented, it would have to be an antisense RNA (also, all of the other options are proteins)

A missense mutation is a type of mutation where a single nucleotide change in the DNA sequence results in the substitution of one amino acid in the protein sequence for another. In this case, the codon AUG, which codes for methionine, is mutated to AAG, which codes for lysine. This change in the DNA sequence leads to the incorporation of lysine instead of methionine in the protein, resulting in a missense mutation.

Answer: B., C. and E. Organic acids are produced by fermentative pathways. Anaerobic respiration does not require oxygen as terminal electron acceptor—this function is taken by other molecules not derived from glycolysis (sulfate, nitrate, fumarate, ferric ion, etc). Anarobic respiration DOES require an ETC (hence cytochromes), an electron acceptor such as sulfate, and will produce a reduced form of that acceptor, such as nitrite.