Wgu Biochemistry Task 1

DNA and RNA
Replication
Deborah J Brooks
Biochemistry (GRT1) Task 1
Western Governors University

Objectives
DNA Replication at Biochemical Level
 Role of Ligase
 Role of mRNA
 Role of RNA Polymerase Inhibition related to the death cap mushroom


Introduction
Nucleic acids are required for the storage and expression of genetic information. There are two chemically distinct types of nucleic acids.
 DNA

(deoxyribonucleic acid). The repository of genetic information.



RNA (ribonucleic acid). “The working copies” of DNA. The copying or translation process in DNA synthesis.

DNA Replication
DNA replication at the biochemical level involves the copying of doubled-stranded DNA to produce a second double helix that is identical to the first
Ligase in DNA Replication
Diagram

Role of mRNA

mRNA Diagram

Polymerase Inhibition and the
Death Cap Mushroom
 This

knowledge of biochemistry of DNA can help to explain how the death cap mushroom poisons an individual who consumes it.

 The

poisonous effect of the death cap mushroom is related to the biochemistry of
DNA and RNA and the process of RNA polymerase inhibition.

Death cap mushroom/Amatoxins
 The

death cap mushroom gives off amatoxins that are toxic to the liver as well as being absorbed from the gastrointestinal tract.  The

main toxin given off by death cap mushroom is ά- amanitine, and there are also nine cyclic 900-Dalton molecular weight octapeptide amatoxins.

Death cap/Polymerase
Inhibition


Shortly after an individual ingest άamanitine, the nucleoli of his/her liver cells will disintegrate, which in turn interferes with DNA transcription because it inhibits
RNA polymerase II.



The way ά-amanitine does this is to bind to the 140,000-Dalton RNA polymerase ll subunit, inhibiting it.



This inhibition effectively stops protein synthesis in the body, so the organs that are most dependent on protein synthesis are the ones that are most sensitive to