Skip to main content

Renin Angiotensin Mechanism.

Transcription or RNA synthesis.

 

Introduction:

  • Transcription is the first step in gene expression. Synthesis of an RNA molecule involves copying the DNA sequence of a gene.

  • RNA polymerases, which link nucleotides to create an RNA strand using a DNA strand as a template, carry out transcription.

  • Transcription has three stages: 

    • initiation, 

    • elongation,

    • termination.

  • Transcription is controlled separately for each gene in our genome.

RNA polymerase:

  • RNA polymerase, the primary enzyme responsible for transcription, builds a complementary strand of RNA using a template made of single-stranded DNA. 

  • Specifically, RNA polymerase builds an RNA strand in the 5' to 3' direction, adding each new nucleotide to the 3' end of the strand.

Initiation:

  • RNA polymerase binds to a sequence of DNA called the promoter, found near the beginning of a gene. 

  • Each gene has its own promoter. 

  • Once bound, RNA polymerase opens the DNA strands, providing the single-stranded template needed for transcription.

Elongation:

  • One strand of DNA, the template strand, acts as a template for RNA polymerase. As it "reads" this template one base at a time, the polymerase builds an RNA molecule from complementary nucleotides, making a chain that grows in reverse, i.e. from 5' to 3'. 

  • The RNA transcript uses the base uracil (U) rather than thymine (T), but it contains the same information as the non-template (coding) strand of DNA.

Termination:

  • Gene sequences called terminators signal that the RNA transcript is complete. 

  • Once they are transcribed, they cause the transcript to be released from the RNA polymerase. 

  • The transcript is called “pre mRNA,” which undergoes modifications.

Modifications of pre mRNA:

  • pre-mRNAs must have their ends modified, by addition of a 5' cap (at the beginning) and a 3' poly-A tail (at the end).

  • Many undergo splicing. 

    • In this process, non essential parts of the pre-mRNA (called introns) are chopped out, and the remaining essential parts (called exons) are joined back together.

  • Modifications increase the stability of the mRNA, while splicing gives the mRNA its correct sequence.

Commonly Asked Questions.

  1. Write a short note on RNA synthesis.

  2. Write a short note on Transcription.
Labels:

Popular posts from this blog

Rate of Drying Curve.

  Definition Drying is defined as the removal of liquid from a product usually with application of heat. Rate of Drying Curve. Drying process can be divided into three periods Initial Adjustment Period. Constant drying rate period. First falling drying rate period. Second falling rate period. Initial Adjustment Period (A-B): Also called the “ Heating up” period . In this period the substance gets heat and increases in temperature. Drying has not yet started. Constant drying rate period (B-C): During this period the temperature of the solid and the rate of drying remain constant. The moisture evaporating from the surface is replaced by water diffusing from the interior of the solid at a rate equal t o the rate of evaporation.  The moisture content at the end of constant rate (point C) is referred to as the critical moisture content (CMC).  At CMC, dry spots start appearing and drying rate starts falling . First falling drying rate period (C-D): This period is also called ...
Read more

Heat Exchangers and Heat Interchangers.

  In pharmaceutical industries many types of equipments are used for transfer of heat, they can be classified as follows, Heat Exchangers. Heat Interchangers. Heat Exchangers: These devices are used for transferring heat from a fluid (Hot Gas or Steam) to another fluid (Liquid) through a metal wall. Heat Interchangers: These devices are used for transferring heat from a One liquid to another liquid or one gas to another gas through a metal wall. HEAT EXCHANGERS; The equipment used for heat transferring are known as heat exchangers. Some of the processes that involves heat transfer in pharmaceutical industries are: Preparation of starch paste (in steam jacketed kettle). Crystallization. Evaporation. Distillation.  Classification of heat exchangers On the basis of transfer of heat, heat exchangers are classified as: Direct transfer type:  The hot and cold fluids are separated by a metal wall through which the heat is transferred from hot fluid to cold fluid. E.g. shell and ...
Read more

Flash Distillation.

  Principle: When a hot mixture is allowed to enter from a high-pressure zone into a low pressure zone, the entire liquid mixture is suddenly vaporized. This process is known as flash vaporization .  During this process, the chamber is cooled.  The less volatile fraction is condensed and the more volatile component remains in the vapor phase .  This process requires time, hence liquid and vapor are kept in intimate contact until equilibrium is achieved. Flash distillation is also called equilibrium distillation because separation of two liquids takes place when liquid and vapor phases are at equilibrium. Equipment used for Flash Distillation: Construction: It consists of a pump, which is connected to a feed reservoir.  Pumps help in pumping the feed into the heating chamber.  The heating chamber is heat supplied by steam.  The other end of the pipe is directly introduced into the vapor-liquid separator through a reducing valve.  The vapor outlet...
Read more