Lec 1 Molecular biology

Dna structure Molecular biology It is old science it contain biochemistry, genetics, microbiology and cell biology Chromosome Very long double strand DNA packed with histone protein, It is very impact structure if you pullout you got contain DNA double strand DNA Language consists 4letters (4nucleotides) that form a lot of words (sequences) DNA on gel (agarose gel electrophoresis) appear fluorescent red bands under UV light due to stacking of ethidium bromide on DNA Gene It is part of DNA (Specific sequence) of DNA about 100bp or may be reach 1500 nucleotide such as 16S ribosomal DNA which is found in bacteria

RNA Contains the sugar (ribose) Contains adenine, uracil, cytosine, cytosine, guanine) Single helix DNA Contains the sugar deoxribose Contains adenine, thymine, cytosine and guanine. Double helix

RNA DNA H Ribose

What type of bond Covalent bonds (Phosphodiester bond ) Hydrogen bonds N base and sugar in nucleotides

Due to present binding between DNA and protein

DNA is negative (- charged) for this unstable but histone protein positive (+charged) neutralize DNA molecular to make it stable. Histone protein of prokaryotes are called basic protein or histone –like protein

Chargaff In 1947, American scientist named chargaff discovered that: The amount of guanine and cytosine bases are equal in any sample of DNA The same is true for the other two nitrogen base The amount of adenine and thymine are equal in any sample of DNA The observation that A=T and that C=G became known as Chargaff rules

Watson and Crick Watson and Crick, 1953 Constructed a model of DNA from Franklin’s X-RAY Diffraction Double-helix model is similar to a teisted ladder 1 – sugar-phosphate backbones make up the sides 2– hydrogen- bonded base make up the rungs ‘steps received a Nobel Prize in 1962