University:
Kentucky State University
Course:
BIO 408 | Cell Biology
Academic year:

2021
Views:

344

Pages:

9
Author:

Carissa Thomas

General description Transcription is the process of making RNA from DNA. One of the two strands of the DNA double helix acts as a template for the synthesis of an RNA molecule. Using DNA strands Although RNA polymerase can read both DNA strands, it uses one strand for any particular gene in order to make RNA. P P P What does determine which strand is used for transcription? Complementary sequences mRNA is complementary to DNA. The RNA chain produced by transcription is also known as the transcript. 5’- 3’- The growing RNA chain is extended in the 5’ to 3’ direction. Enzyme and substrate The enzymes that perform transcription are called RNA polymerases. RNA polymerases catalyze the formation of the phosphodiester bonds between two nucleotides. The substrates are nucleoside triphosphates (ATP, CTP, UTP, and GTP). A hydrolysis of high-energy bonds in NTP provides the energy needed to drive the reaction forward. Polysomes As RNA is synthesized, it is initially bonded to DNA, but after a short distance, the older polymerized RNA nucleotides are separated, and the newer ones become bonded This allows the simultaneous synthesis of many RNA chains from the same gene forming structures known as polysomes DNA replication vs. transcription The RNA strand does not remain hydrogen-bonded to the DNA template strand. RNA polymerase read the A in DNA and inserts U in the growing chain of RNA rather than T. RNA molecules are much shorter than DNA molecules. Unlike DNA, RNA does not store genetic information in cells. DNA polymerase vs. RNA polymerase RNA polymerase catalyzes the linkage of ribonucleotides, not deoxyribonucleotides. Unlike DNA polymerases, RNA polymerases can start an RNA chain without a primer. RNA polymerases make about one mistake for every 104 nucleotides. the consequences of an error in RNA transcription are much less significant than that in DNA replication. Although RNA polymerases are not as accurate as the DNA polymerases, they have a modest proofreading mechanism.