NUCLEIC ACIDS Dr. Gamal Gabr, College of Pharmacy.

NUCLEIC ACIDSNUCLEIC ACIDS

Dr. Gamal Gabr, College of Pharmacy


Deoxyribonucleic acid (DNA), which stays in the cell nucleus, and Ribonucleic acid (RNA), which functions in the cell cytoplasm.

Store and pass on essential genetic information that controls reproduction and protein synthesis.

DNA molecules are made up of the nitrogen-containing bases adenine, guanine, cytosine, and thymine; phosphoric acid (H3PO4); and the simple sugar commonly called deoxyribose.

RNA molecules are composed of the nitrogen-containing bases adenine, guanine, cytosine, and uracil; phosphoric acid (H3PO4); and the simple sugar ribose.


Nucleotide structure

Nucleotides are composed of a nitrogenous base, a pentose monosaccharide, and one, two, or three phosphate groups.

The nitrogen-containing bases belong to two families of compounds: the purines and the pyrimidines.

Both DNA and RNA contain the same purine bases: adenine (A) and guanine (G). Both DNA and RNA contain the pyrimidine cytosine (C), but they differ in their second pyrimidine base: DNA contains thymine (T), whereas RNA contains uracil (U).


Nucleosides

The addition of a pentose sugar to a base produces a nucleoside. If the sugar is ribose, a ribonucleoside is produced; if the sugar is 2-deoxyribose, a deoxyribonucleoside is produced. The ribonucleosides of A, G, C, and U are named adenosine, guanosine, cytidine, and uridine.

NucleotidesThe addition of one or more phosphate groups to a nucleoside produces a nucleotide.


Digestion of nucleic acids

The nucleic acids in the diet are hydrolyzed to a mixture of nucleotides by ribonuclease and deoxyribonuclease presents in pancreatic and intestinal secretions. Then the nucleotidases liberate the phosphate from nucleotides. The resulting nucleosides are hydrolysed by nucleosidases forming free bases and pentose sugars. Even when humans consume a diet rich in nucleoproteins, dietary purines and pyrimidines are not incorporated directly into tissue nucleic acids. Humans synthesize the nucleic acids, ATP, NAD+, coenzyme A, from amphibolic intermediates


Constituents of DNA and RNA


Nucleoside + phosphate yields phosphate ester nucleotide.


Polymerized nucleotide yields nucleic acidIn the nucleic acid the phosphate negative charges are neutralized by metal cations (such as Mg2+) or positively charged proteins (histones).


It was figured out in 1953 by James D. Watson, an American scientist, and Francis Crick, a British scientist.

This model visualizes DNA as a so called double á-helix structure of oppositely wound polymeric strands held together by hydrogen bonds between opposing pyrimidine and purine groups.

In the secondary structure of DNA, only cytosine can be opposite guanine and only thymine can be opposite adenine and vice versa.

The two strands of DNA are complementary. This means that a particular portion of one strand fits like a key in a lock with the corresponding portion of another strand.

Nucleic Acids in Protein Synthesis


When a new cell is formed, the DNA in its nucleus must be accurately reproduced from the parent cell.

Life processes are absolutely dependent upon accurate protein synthesis, as regulated by cell DNA

The DNA in a single cell must be capable of directing the synthesis of up to 3000 or even more different proteins.

The directions for the synthesis of a single protein are contained in a segment of DNA called a gene.

The process of transmitting information from DNA to a newly synthesized protein involves the following steps:

Nucleic Acids in Protein Synthesis


1) The DNA undergoes replication: This process involves separation of a segment of the double helix into separate single strands. This process continues until a complete copy of the DNA molecule has been produced.

2) The newly replicated DNA produces messenger RNA (mRNA), a complement of the single strand of DNA, by a process called transcription.

3) A new protein is synthesized using mRNA as a template to determine the order of amino acids in a process called translation.

RECOMBINANT DNA AND GENETIC ENGINEERING

Segments of DNA contain information for the specific syntheses of particular proteins.

it has become possible to transfer this information between organisms by means of recombinant DNA technology, which has resulted in a new industry based on genetic engineering.

Most often the recipient organisms are bacteria, which can be reproduced (cloned) over many orders of magnitude from a cell that has acquired the desired qualities.

Therefore, to synthesize a particular substance, such as human insulin or growth hormone, the required genetic information can be transferred from a human source to bacterial cells, which then produce the substance as part of their metabolic processes.


The first step in recombinant DNA gene manipulation is to lyze (open up) a donor cell to remove needed DNA material by using enzyme action to cut the sought-after genes from the donor DNA chain.

These are next spliced into small DNA molecules. These molecules, called cloning vehicles, are capable of penetrating the host cell and becoming incorporated into its genetic material.

The modified host cell is then reproduced many times and carries out the desired biosynthesis.


Three types of RNA involved in comprising the structural and functional core for protein synthesis, serving as a template for translation, and transporting amino acid, respectively, are: mRNA, tRNA, rRNA

With 3'-AUG-5‘ mRNA codon would the tRNA in the diagram be able to form a codon-anticodon base pairing interaction

A gene is a segment of DNA that codes for a protein mRNA takes the genetic code to the cytoplasm The three nucleotide sequence on RNA is called a codon In the ladder anology of the DNA molecule, the "rungs" of

the ladder are paired nitrogenous bases The enzymes that break hydrogen bonds and unwind DNA

are helicases


Transcription results in messenger RNA In RNA, one codon translate to one amino acid

NUCLEIC ACIDS Dr. Gamal Gabr, College of Pharmacy.

Documents

Transcript of NUCLEIC ACIDS Dr. Gamal Gabr, College of Pharmacy.