Nucleic acids (DNA & RNA)

to conform to X-ray data
In April 1953, James Watson and

Francis Crick shook the scientific world with an elegant double-helical model or the structure of deoxyribonucleic acid or DNA.

Watson and Crick began to work on a model of DNA with two strands, the double helix.

store and transmit hereditary information.
There are two types of nucleic

acids:
1)- ribonucleic acid (RNA);
2)- deoxyribonucleic acid (DNA).
DNA also directs mRNA synthesis, thus, controls protein synthesis.
Organisms inherit DNA from their parents.
Each DNA molecule is very long and usually consists of hundreds to thousands of genes.
When a cell divides, its DNA is copied and passed to the next generation of cells.
The mRNA interacts with ribosomes to direct the synthesis of amino acids in a polypeptide (protein)

attached to the sugar of the next nucleotide in line.

The

result is a “backbone” of alternating phopates and sugars, from which the bases starts.

are polymers of monomers called nucleotides.

Each nucleotide consists of three

parts: a nitrogen base, a pentose sugar, and a phosphate group.

The nitrogen bases (rings of carbon and nitrogen) come in two types: Purines and Pyrimidines.

The pentose sugar joined to the nitrogen base is ribose in nucleotides of RNA and deoxyribose in DNA.

The only difference between the sugars is the lack of an oxygen atom on carbon 2 in deoxyribose.

to the phosphate of the next with a phosphodiester link.

This

creates a repeating backbone of sugar-phosphate units with the nitrogen bases as appendages.

The sequence of nitrogen bases along a DNA or mRNA polymer is unique for each gene.

Genes are normally hundreds to thousands of nucleotides long.

The linear order of bases in a gene specifies the order of amino acids (the monomers of a protein).

have two polynucleotide strands (double strand) that spiral around to

form a double helix.

outside of the helix.

Pairs of nitrogenous bases (one from each

strand) connect the polynucleotide chains with hydrogen bonds.

Most DNA molecules have thousands to millions of base pairs (bP).

construction of a protein.

b)- Ribosomal RNA (rRNA) is the

construction site where the protein is made in the ribosome.

c)- Transfer RNA (tRNA) is the truck delivering the proper amino acid to the site at the right time.

RNA
Ribo-Nucleic-Acid
Deoxiribo-Nucleic-Acid