BT-202Netaji Subhas Institute of Technology,

Dwarka, New Delhi.Dr. Amita Pandey

Sept 14, 2011

• Nucleotide• Nucleoside

• 2’-deoxy-D-ribose• D-ribose

• Pyrimidines• Purines

Deoxyribonucleotide:-dAMP-dGMP-dTMP-dCMP

Ribonucleotide:-AMP-GMP-UMP-CMP

Nucleoside:-Deoxyadenosine-Deoxyguanosine-Deoxythymidine-Deoxycytidine

Nucleoside:-Adenosine-Guanosine-Uridine-Cytidine

• Minor bases -methylated-hydroxymethylated-glycosylated

Phosphodiester bond

Hydrolysis of RNA molecules

Mixture of 2’- and 3’-monophoaphate

derivatives

• Oligonucleotide-50 nucleotides polymer

• Polynucleotide-longer polymers

DNA structure by Watson and Crick1953

-hydrophobic interactions-van der Waals interactions-dipole-dipole interactions

-hydrogen bonds

• Primary structure: -nucleotide sequence

• Secondary structure:-stable structure taken up by nucleotides

• Tertiary structure:-folding of chromosomes

Frederich Miescher (1868): isolated and characterized DNA from leukocytes and called it “nuclein”. He found that it was rich in phosphorus and nitrogen.

O. T. Avery, C. MacLeod, and M. McCarty (1940s): first time said DNA was the genetic material.

A.D. Hershey and M. Chase (1952): confirmed that DNA not protein is the genetic material.

E. Chargaff (1940s): “Chargaff’s rules” he said that A = T and G = C.

R. Franklin and M. Wilkins (1950s): DNA molecules are helical with two periodicities along their long axis.

Watson and Crick (1953):

-hydrophillic phosphate and deoxyribose on outside -hydrophobic bases on inside-two grooves-hydrogen bonding between base pair-antiparallel-10.5 bp in each turn-complementary

Complementarity laid the foundation for DNA replication

B-form is the most stable

A form B-form Z-form

-A-form arises dehydration

-Z-form is detectable in both bacteria and eukaryotes

• Palindrome• Mirror repeats• Hairpins• Cruciforms

• Triplex DNA• G tetraplex

Hoogstein pairing

• F. Jacob and J. Monod (1961): proposed the name messenger RNA.

• Transcription: process of forming mRNA on DNA template.

• Monocistronic: mRNA encoding a single polypeptide.

• Polycistronic: mRNA encoding for more than one polypeptide.

mRNA

G pairs with C and A pairs with U

• A-form of RNA is predominant form• Hairpins are most common secondary structures

• rRNA: provides peptidyl transferase activity during translation– Large subunit (LSU): 18S rRNA– Small subunit (SSU): 5S, 5.8S, and 28S rRNAs

Reversible denaturation and annealing of DNA

-viscosity of DNA-pH-temperature

-absorption of UV light-hypochromic effect-hyperchromic effect

• Melting point tm

-higher GC content higher

melting temp

Partially denatured DNA

Hybridization

• Hybrid duplexes-temperature-evolutionary relationship

• Southern hybridization

• Northern hybridization

Mutations

Alteration in DNA structure that produce permanent changes in the genetic information

-deamination cytosine undergoes deamination spontaneously

Adenine deaminates to HypoxanthineGuanine deaminates to Xanthine

-depurination-apurinic or apyrimidinic

• Radiation-cyclobutane pyrimidine dimers-6-4 photoproduct

• Ionizing radiation-ring opening-fragmentation of bases

• Chemicals-deaminating agents eg. Nitrous acid-alkylating agents

• Oxidative damage-hydrogen peroxide, hydroxyl radicals, and superoxide radicals

Learning check!

• Phosphatidylethanolamine has a net charge of at pH 7.0.zero

• Lipids molecules are the only essential components of biological membranes.TrueFalse

• Lipids in bilayer have high ratio of diffusion.lateral

• Palmitic acid is a acid.fatty

• Match Glycerophospholipids CholesterolSphingolipids PhosphatidylcholineSteroid Spingomyelin

• Lipids containing hydrocarbon chain serve as energy stores.TrueFalse

• Ergosterol is a glucorticoid.TrueFalse

• Polyunsaturated Fas contain multiple bonds.double

• Phospholipases are enzymes that catalyze of glycophospholipids.hydrolysis

• Which of the following is not a complex lipidTriacylglycerolGlycolipidsSphingolipidsPhospholipids

• Sphingolipids are significant components of biological membranes.TrueFalse

• Which FA would have a melting temperaturehigher than palmitic acid (16:0)?Myristic acid (14:0)Palmitic acid (16:1)Oleic acid (18:1)Stearic acid (18:0)

Assignment # 4

Lehninger:Question 2, 5, 6, 8, and 9.