Unit 4 Chee 370

The sigma factor is a protein that plays a crucial role in initiating transcription in bacteria. It recognizes and binds to a specific region on the DNA molecule called the promoter. The promoter region contains specific DNA sequences that serve as binding sites for the sigma factor and help recruit the RNA polymerase enzyme to initiate transcription. By tightly binding the polymerase to the promoter, the sigma factor ensures the efficient and accurate initiation of transcription.

RNA polymerase does not require the energy of ATP hydrolysis to open the helix. While DNA helicase uses ATP hydrolysis to separate the DNA strands during replication, RNA polymerase does not have this requirement. RNA polymerase is responsible for synthesizing RNA from a DNA template, and it does so by unwinding the DNA helix without the need for ATP hydrolysis. Therefore, the statement is false.

When polymerase starts without a free 3'OH end, it is called "de novo." This term refers to the synthesis of a new DNA strand without the use of a pre-existing template. In this case, the polymerase is not able to accurately incorporate the nucleotides, leading to a lower level of accuracy in the replication process.

During transcription, bacterial RNA polymerase will continue RNA chain elongation down the strand until it encounters the signal of the rho factor. The rho factor is a protein that plays a role in termination of transcription in bacteria. It binds to the mRNA transcript and causes the RNA polymerase to dissociate from the DNA template, leading to the release of the newly synthesized RNA molecule. This termination signal is important for proper regulation of gene expression and the production of functional RNA molecules.

The Pribnow box and the 35 sequence are indeed regions in prokaryotic promoters. These regions are important for the binding of RNA polymerase and initiation of transcription. The Pribnow box, also known as the -10 sequence, is a conserved sequence located 10 base pairs upstream of the transcription start site. It is recognized by the sigma factor of RNA polymerase, facilitating the binding of RNA polymerase to the promoter. The 35 sequence, located 35 base pairs upstream of the transcription start site, is another conserved sequence that helps in the recognition and binding of RNA polymerase. Therefore, the statement is true.

The bacterial transcription termination sequence is a long string of A-T pairs, and then an inverted repeat sequence that forms a hairpin structure when transcribed into RNA. This is because A-T pairs have only two hydrogen bonds, making them easier to separate during transcription. The inverted repeat sequence allows the RNA to fold back on itself, forming a hairpin structure that signals the termination of transcription.

The correct answer is that EUKARYOTIC RNA polymerase needs many proteins called general transcription factors for initiation, there are three, only one is generally used for transcribing genes/proteins, and transcription initiation has to deal with packing DNA into nucleosome and chromatin structure. This means that in eukaryotes, RNA polymerase requires the assistance of multiple general transcription factors to initiate transcription. There are three different types of RNA polymerases in eukaryotes, but only one of them is generally used for transcribing genes/proteins. Additionally, transcription initiation in eukaryotes involves dealing with the packaging of DNA into nucleosomes and the overall chromatin structure.

An open reading frame refers to a sequence of DNA or RNA that can be translated into a protein. It starts with a start codon (usually AUG) and continues until a stop codon is encountered. In this context, the statement is saying that an open reading frame is the part of a reading frame that does not contain a stop codon. This means that it can potentially be translated into a protein. Therefore, the correct answer is true.

They have 30 to 40. Eukaryotes have 50 to 100.

The TATA box is a specific sequence known as a promoter, which plays a crucial role in initiating transcription. It is recognized by the TFIID factor, which helps recruit other transcription factors and RNA polymerase to the promoter region. The TATA box is located 25 nucleotides upstream from the transcription start site, meaning it is positioned before the start of transcription.

This is characteristic of eukaryotes only

Polycistronic mRNA is a type of mRNA that contains multiple coding sequences or genes within a single transcript. This mRNA structure is commonly found in prokaryotes, such as bacteria, where multiple genes can be transcribed and translated together to produce multiple proteins. However, in eukaryotes, including plants and animals, mRNA is typically monocistronic, meaning it contains only one coding sequence or gene per transcript. Therefore, the statement that polycistronic mRNA is found in eukaryotes is untrue.

The three sites in the large ribosomal subunit are A, P, and E. These sites play a crucial role in protein synthesis. The A site (aminoacyl site) is where the incoming aminoacyl-tRNA binds to the ribosome. The P site (peptidyl site) is where the growing polypeptide chain is held. The E site (exit site) is where the tRNA that has released its amino acid exits the ribosome. These sites work together to ensure the accurate and efficient translation of the mRNA sequence into a protein.

The spliceosome is responsible for removing introns from pre-mRNA during the process of splicing. It is a complex made up of small nuclear ribonucleoproteins (snRNPs) and other proteins. The spliceosome recognizes specific sequences at the ends of introns and catalyzes the removal of these non-coding regions. This allows the exons to be joined together, forming the mature mRNA molecule that can be translated into protein. The other options, endonuclease, RNA Polymerase I, and general transcription factors, are not directly involved in the removal of introns.

adds a 3' cap

A consensus sequence is derived by comparing many sequences with the same basic function and finding the most common nucleotide found at each position. This means that the consensus sequence represents the most frequently occurring nucleotide at each position in a set of related sequences. It provides a representation of the majority or consensus nucleotides at each position, which can be useful for understanding the common features or patterns within a group of sequences.

A degenerate code refers to the fact that multiple codons can code for the same amino acid. This is possible because there are 64 possible codons (combinations of three nucleotides) and only 20 amino acids, so some amino acids are represented by more than one codon. This redundancy in the genetic code allows for flexibility and robustness in protein synthesis, as mutations or errors in the DNA sequence may not always result in a change in the amino acid sequence of the protein.

Peptidyl transferase is an enzyme found in the ribosome that catalyzes the formation of a peptide bond between two amino acids during protein synthesis. It is responsible for joining the amino acids together to form a growing polypeptide chain. Therefore, the statement that peptidyl transferase creates the peptide bond between the amino acids in the ribosomal sites is true.

tRNAs, or transfer RNAs, are molecules that play a crucial role in protein synthesis. They are responsible for carrying amino acids to the ribosome during translation. tRNAs are known for their unique cloverleaf structure, which is formed by base pairing within the molecule. Due to their complex structure and the need to accommodate various amino acids, tRNAs are approximately 80 nucleotides long. This length allows for the necessary folding and flexibility required for their function in protein synthesis.

In tRNA, the amino acid binding site is located at the 3' end. This is where the amino acid is covalently attached to the tRNA molecule through an ester bond. The 3' end of the tRNA molecule contains a specific sequence of nucleotides called the CCA sequence, which serves as the binding site for the amino acid. This binding is essential for the correct pairing of tRNA with its corresponding codon during protein synthesis.

The statement is true because some amino acids have multiple codons that can code for them. Each codon is recognized by a specific tRNA molecule, so if an amino acid has multiple codons, it will also have multiple matching tRNA molecules. This allows for redundancy in the genetic code and ensures that the correct amino acid is incorporated into the growing protein chain during translation.

It comes from GTP

They are modified before they leave the nucleus

Eukaryotic tRNAs are synthesized by RNA Polymerase III. This enzyme is responsible for transcribing genes that encode transfer RNA molecules. RNA Polymerase III recognizes specific DNA sequences called promoters, located upstream of tRNA genes, and initiates transcription by synthesizing a complementary RNA molecule. This process ensures the production of mature tRNAs that are essential for protein synthesis in eukaryotic cells. RNA Polymerase I and II are involved in the transcription of other types of RNA molecules, while DNA Polymerase is responsible for DNA replication, not RNA synthesis.

Amino acids are coupled to their tRNA molecules by aminoacyl-tRNA synthetase. This enzyme is responsible for attaching the correct amino acid to its corresponding tRNA molecule, ensuring that the correct amino acid is incorporated into the growing polypeptide chain during protein synthesis. The aminoacyl-tRNA synthetase recognizes both the specific amino acid and the specific tRNA molecule, forming a high-energy bond between them. This process is essential for accurate protein synthesis and is a crucial step in the central dogma of molecular biology.

Proteins are synthesized from their N-terminal (amino) end to their C-terminal (carboxyl) end. This means that during protein synthesis, amino acids are added one by one to the growing polypeptide chain starting from the N-terminal end and extending towards the C-terminal end. This process is guided by the genetic information encoded in the mRNA molecule.

Protein synthesis is a complex process that involves the translation of the genetic code into a protein sequence. However, due to various factors such as errors in DNA replication or mutations, mistakes can occur during this process. The given answer, 10,000 amino acids, suggests that protein synthesis has approximately one mistake in every 10,000 amino acids. This indicates that the overall accuracy of the process is relatively high, with only a small fraction of amino acids being affected by errors.

RNA polymerases don't have a proofreading mechanism, unlike DNA polymerases. Proofreading is the process by which DNA polymerases can detect and correct errors in the newly synthesized DNA strand. RNA polymerases, on the other hand, do not possess this ability, which makes them more prone to errors during transcription. This lack of proofreading mechanism is one of the key differences between RNA polymerase and DNA polymerase.

Protein synthesis occurs in the ribosome. The ribosome is a cellular structure responsible for translating the genetic information from the DNA into proteins. It is composed of RNA and proteins and is found in the cytoplasm of a cell. The ribosome reads the messenger RNA (mRNA) molecule and uses it as a template to assemble amino acids into a polypeptide chain, which then folds into a functional protein. This process is essential for the growth, development, and functioning of all living organisms.

The start codon for translation of mRNA is AUG. This codon serves as the signal for the ribosome to begin protein synthesis. It codes for the amino acid methionine, which is often the first amino acid in a protein chain. The AUG codon is recognized by the initiation complex, which helps to assemble the ribosome and initiate translation.

The tRNA that carries the start codon is called methionine. Methionine is an amino acid that serves as the initiator for protein synthesis. It is encoded by the start codon AUG in mRNA. The tRNA molecule that recognizes and binds to this start codon is specifically designed to carry methionine and bring it to the ribosome, where translation begins. This tRNA molecule ensures that the correct amino acid is positioned at the start of the growing polypeptide chain during protein synthesis.

This is the error rate of RNA polymerization. Replication has an error rate of 1 in 10^9

Okazaki fragments are short, newly synthesized DNA fragments that are formed on the lagging strand during DNA replication. These fragments are created in a discontinuous manner due to the antiparallel nature of DNA. Each Okazaki fragment is typically about 1000 to 2000 nucleotides long.

Eukaryotes have eukaryotic initiation factors to initiate translation.

The possible stop codons in the given options are UAA, UAG, and UGA. Stop codons are sequences of nucleotides in mRNA that signal the end of protein synthesis. When a ribosome encounters a stop codon, it releases the newly synthesized protein and detaches from the mRNA molecule. UAA, UAG, and UGA are recognized as stop codons by the ribosome, causing the termination of translation. GUA is not a valid stop codon, as it does not conform to the standard genetic code.