Transcription is the one of the two stage involved in gene expression. It involves the synthesis of a mRNA molecule using a DNA template. The process of transcription is carried out by an enzyme called RNA polymerase which binds to the PROMOTER region of the DNA molecule and begins to synthesize RNA nucleotides based on what it reads on the DNA.
The addition of nucleotide bases on the RNA strand by RNA polymerase enzyme follows the COMPLEMENTARY BASE PAIRING RULE, which states that Adenine always pairs with Thymine while Guanine always pairs with Cytosine in a DNA molecule. In the case of transcription, the Uracil base replaces Thymine in the newly synthesized RNA. Hence, for every Adenine nucleotide read by RNA polymerase, it adds a Uracil nucleotide. The same goes for Thymine-Adenine, Cytosine-Guanine and Guanine-Cytosine i.e. A-U, G-C.
Based on this principle, a DNA template with a sequence: TGGCAAGTACGT will produce an mRNA molecule with sequence: ACCGUUCAUGCA
The protective covering of the brain
that provides passageways for cerebrospinal fluid (CSF) to drain into the
superior sagittal sinus is called the arachnoid mater.
To add, the arachnoid mater is the middle
of three layers that make up the meninges, or membranes, that surround the spinal
cord and brain.
