Transcription

-

 Transcription is a fundamental biological process in which the genetic information in a DNA sequence is copied into a complementary RNA sequence. This is the first step in gene expression, leading to the production of proteins.

Steps of Transcription

Initiation

Transcription begins when RNA polymerase, an enzyme, binds to a specific DNA region called the promoter.

The promoter is located upstream of the gene that is to be transcribed. The binding of RNA polymerase to the promoter causes the DNA to unwind, forming a small open complex known as the transcription bubble.

Elongation:

RNA polymerase moves along the DNA template strand in the 3’ to 5’ direction, synthesizing a single-stranded RNA molecule in the 5’ to 3’ direction.

As it moves, RNA polymerase adds RNA nucleotides (adenine, uracil, cytosine, and guanine) complementary to the DNA template strand. For example, if the DNA has a cytosine (C), the RNA will have a guanine (G).

Termination:

Transcription continues until RNA polymerase reaches a terminator sequence on the DNA.

The RNA polymerase detaches from the DNA, and the newly synthesized RNA strand, now called messenger RNA (mRNA), is released.

RNA Processing (in eukaryotes):

After transcription, the mRNA undergoes processing, which includes:

Capping: Addition of a 7-methylguanylate cap to the 5’ end of the mRNA.

Polyadenylation: Addition of a poly-A tail to the 3’ end of the mRNA.

Splicing: Removal of non-coding regions (introns) and joining of coding regions (exons) to produce a mature mRNA molecule ready for translation.

Importance of Transcription:

Transcription is crucial because it is the step that converts the genetic information stored in DNA into a format that can be used to make proteins, which are essential for the structure, function, and regulation of the body’s tissues and organs. The mRNA produced during transcription serves as a template for the next step, translation, where the genetic code carried by the mRNA is used to synthesize proteins.

 


Comments

Post a Comment

Popular posts from this blog

Staphylokinase (Sak) and Streptokinase (SK)

-
Staphylokinase (Sak)  and  Streptokinase (SK)  are fascinating enzymes with a dual identity—used both in medicine and by bacteria as virulence factors. Medically, streptokinase (produced by  Streptococcus pyogenes ) has long been used as a clot-dissolving drug in conditions like heart attacks, deep vein thrombosis, and pulmonary embolism. It is cost-effective but has notable drawbacks, including a high risk of systemic bleeding due to its non-specific action and the potential to trigger immune reactions, especially upon repeated use. In contrast, staphylokinase (from  Staphylococcus aureus ) is still under clinical investigation but shows promise as a more clot-specific alternative, acting mainly at the site of clots and posing a lower bleeding risk. However, its clinical application is limited so far due to slower activation and ongoing trials. From a pathogenic standpoint, both enzymes help bac...
Read more

Activation of Yellow marrow into Red marrow

-
 When the body senses a shortage of blood cells , it sends signals to reactivate the yellow bone marrow. 1. Detection of Blood Cell Shortage In conditions like anemia , injury , or infection , there are not enough red blood cells (RBCs) or other blood cells. The body detects low oxygen levels or low cell counts in the blood.  2. Signal Release The kidneys release a hormone called erythropoietin (EPO) . Cytokines (immune signaling proteins) are also released. These signals reach the bone marrow through the blood.  3. Stem Cell Activation in Yellow Marrow The yellow marrow contains mesenchymal stem cells (fat-storing stem cells). Under normal conditions, these produce fat. But in response to signals (like EPO and cytokines), they start converting into hematopoietic cells (blood-producing cells). 4. Fat Cells Decrease Fat cells in yellow marrow shrink or die off . More space opens up for blood-forming cells to grow. 5. Re...
Read more

Complement system

-
  Complement system is significant part of innate immune system.it contains 30 proteins in blood plasma and on the surface of the cell which will activate as a chain reaction (one will activate the next) Following are the major functions of complement system. Opsonization- label the microbes so that the phagocytic cells will get activated Chemotaxis-Attract the immune cells to the infected site Cell lysis- Forms a membrane attack complex (MAC) that can directly kill bacteria Clearance of Immune complexes- Helps to remove  antibody antigen complex from the body Pathways 1. Classical pathway classical pathway will be triggered by the antibodies and it comes under the part of adaptive immunity. Example If a person got infected with the measles virus . The body will start produced IgG antibodies against the virus. These antibodies bind to the virus. The classical pathway is activated to destroy the virus . classical pathway needs antibodies to induce the immune response . 2. Lect...
Read more