what are differences of transcription factors between prokaryotic.pdf

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arri2009av

Water being diverted during a flood in Helsinki, Finland (latitude 60°N) flows along a diversion channel of width 47 m in the south direction at a speed of 3.4 m/s. On which side is the water the highest (from the standpoint of noninertial systems) and by how much? Solution That angle of the water surface is tan alpha = 2 w v cos theta / g = (2 * 2 pi * 3.4 * cos 60) / (9.8) * (24 * 60) = 4.36 * 10-5 rad The difference in height of the water on the two sides is = w * tan alpha = 47 * 4.36 * 10-5 = 2.05 mm.

Education

what are differences of transcription factors between prokaryotic and eukaryotic
microorganisms
what are differences of transcription factors between prokaryotic and eukaryotic
microorganisms
Solution
Prokaryotes contain a single type of RNA polymerase, while eukaryotes (multicellular organisms
and yeasts) contain three distinct types.
Transcription in Prokaryotes
In prokaryotes, all transcription is performed by a single type of RNA polymerase. This
polymerase contains four catalytic subunits and a single regulatory subunit known as sigma (s).
Several distinct sigma factors have been identified, and each of these oversees transcription of a
unique set of genes. Sigma factors are thus discriminatory, as each binds a distinct set of
promoter sequences.
Transcrption in eukaryotes
in eukaryotes, transcription is achieved by three different types of RNA polymerase (RNA pol I-
III). These polymerases differ in the number and type of subunits they contain, as well as the
class of RNAs they transcribe; that is, RNA pol I transcribes ribosomal RNAs (rRNAs), RNA
pol II transcribes RNAs that will become messenger RNAs (mRNAs) and also small regulatory
RNAs, and RNA pol III transcribes small RNAs such as transfer RNAs (tRNAs).

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Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation, and expression of genes. RNA and DNA are nucleic acids, and, along with proteins and carbohydrates, constitute the four major macromolecules essential for all known forms of life. Like DNA, RNA is assembled as a chain of nucleotides, but unlike DNA it is more often found in nature as a single-strand folded onto itself, rather than a paired double-strand.

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• Define transcription • Define translation • What are the 3 steps of translation? • Define the “genetic dogma” • What is the function of Transfer RNA? • What is the function of RNA polymerase? • What is the function of DNA polymerase? • Define “splicing of RNA” • What is an exon? • What component of the cell does the translation? • What molecule in the cell does transcription? • What are the functions of: operon, promotor? • What is the difference between inducible operon and repressible operon? Solution • Define transcription Transcription is the process of making an RNA copy of a gene sequence. This copy, called a messenger RNA (mRNA) molecule, leaves the cell nucleus and enters the cytoplasm, where it directs the synthesis of the protein, which it encodes. Here is a more complete definition of transcription. • Define translation Translation is the process of translating the sequence of a messenger RNA (mRNA) molecule to a sequence of amino acids during protein synthesis. The genetic code describes the relationship between the sequence of base pairs in a gene and the corresponding amino acid sequence that it encodes. In the cell cytoplasm, the ribosome reads the sequence of the mRNA in groups of three bases to assemble the protein. Here is a more complete definition of translation: • What are the 3 steps of translation? Step # 1. Initiation: Initiation of translation in E .coli involves the small ribosome subunit, a mRNA molecule, a specific charge initiator tRNA, GTP, Mg++ and number of proteinaceous initiation factors (IFs). These are initially part of the small subunit and are required to enhance binding affinity of the various translational components (Table 8.1). Unlike ribosomal proteins, IFs are released from the ribosome once initiation is completed. Step # 2. Elongation: Once both subunits of the ribosome are assembled with the mRNA, binding site for two charged tRNA molecules are formed. These are designated as the ‘P’ or peptidyl and the ‘A’ or aminoacyl sites. The charged initiator tRNA binds to the P site, provided that the AUG triplet of mRNA is in the corresponding position of the small subunit. The increase of the growing polypeptide chain by one amino acid is called elongation. Step # 3. Termination: Termination of protein synthesis is carried out by triplet codes (UAG, UAA, UGA; stop codons) present at site A. These codons do not specify an amino acid, nor do they call for a tRNA in the A site. These codons are called stop codons, termination codons or nonsense codons. The finished polypeptide is still attached to the terminal tRNA at the P site, and the A site is empty. • Define the “genetic dogma” A theory in genetics and molecular biology subject to several exceptions that genetic information is coded in self-replicating DNA and undergoes unidirectional transfer to messenger RNAs in transcription which act as templates for protein synthesis in translation • What is the function of Transfer RNA? The tRNA molecule, or tr.

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