DNA STRUCTURE, GENETIC CODE, CHROMOSOMES MOLECULAR BIOLOGY – DNA structure, genetic code

GENES ARE ON CHROMOSOMES proteins DNA MOLECULAR BIOLOGY – DNA structure, genetic code

DNA STRUCTURE DISCOVERY MOLECULAR BIOLOGY – DNA structure, genetic code

James D. Watson 15 years old accepted to university 22 years old received Ph.D. in zoology at Indiana University, Bloomington 1950 research stay in Danmark attended a conference in Napoli Lecture by Maurice Wilkinse (Kings College of London) - study of DNA structure by X-ray diffraction MOLECULAR BIOLOGY – DNA structure, genetic code

Cavendish Laboratory, Cambridge Watson: study of 3D-structure of myoglobine Francis Crick 33 years old still Ph.D. student study of hemoglobine MOLECULAR BIOLOGY – DNA structure, genetic code

DNA STRUCTURE SHOULD FIT INTO 4 PRINCIPLES: 1. DNA has to be repricable 2. DNA code an information 3. Cell regulation depends on DNA 4. DNA changes by mutations MOLECULAR BIOLOGY – DNA structure, genetic code

Chemical composition of DNA was known: 5-carbon sugar Nitrogen containing base Phosphate 4 bases: adenine, guanine, thymine, cytosine DNA long polymere MOLECULAR BIOLOGY – DNA structure, genetic code

Linus C. Pauling ( ) 3D structure of proteins by X-ray crystalography alfa-keratine alfa-helix found everywhere Models of aminoacids cut from paper plausible 3-D models could be built from knowledge of chemical bonding and bond distances to fit experimental data. MOLECULAR BIOLOGY – DNA structure, genetic code

Rosalind E. Franklin ( ) Colleague of Wilkins Chemist with rich experience in X-ray crystalography MOLECULAR BIOLOGY – DNA structure, genetic code

X-ray crystalography MOLECULAR BIOLOGY – DNA structure, genetic code

NOVEMBER 1951 – seminar by Rosalind Franklin Watson attended the seminar built the first model – an embarassing failure (Watson's faulty report of the data presented at the seminar )

1952 PHOTOGRAPHY 51 Wilkins and Astbury mixture of dry and wet forms of DNA crystal (today A & B) no clear photography 1) the distance between bases (3.4A) 2) the length of the period (34A) 3) the rise of the helix (36 degrees)

MOLECULAR BIOLOGY – DNA structure, genetic code January 1953 Maurice Wilkins James D. Watson Watson: "The instant I saw the picture my mouth fell open and my pulse began to race" HELIX! February 1953 Franklin’s Report for Medical Research Council Max Perutz Francis Crick two strands run in opposite directions

Aren’t the hydrogen bonds too weak? Mathematician John Griffith, friend of Crick: based on chemical principles and qantum mechanics calculated the attractive forces between bases A T a G C (Crick did not know about the Chargaff’s rule A/T G/C) Watson: MOLECULAR BIOLOGY – DNA structure, genetic code

ENOL FORMKETO FORMS 2 TAUTOMERIC FORMS Jerry Donohue MOLECULAR BIOLOGY – DNA structure, genetic code

DNA STRUCTURE SOLVED! (without even one own experiment) MOLECULAR BIOLOGY – DNA structure, genetic code

1962 Nobel price : Francis Crick, James Watson a Maurice Wilkins 1958 (37 years) Rosalind E. Franklin MOLECULAR BIOLOGY – DNA structure, genetic code

5-carbon sugar Nitrogen containing base Phosphate 4 bases: adenine, guanine, thymine, cytosine D EOXYRIBO N UCLEIC A CID - DNA MOLECULAR BIOLOGY – DNA structure, genetic code

5’end 3’end H CH DNA strands have direction: DNA polymerase synthesis 5’ AGCTGGCTCGAACGTCGAT 3’ 3’ TCGACCGAGCTTGCAGCTA 5’ MOLECULAR BIOLOGY – DNA structure, genetic code

REPLICATION: Meselson-Stahl experiment heavier isotope 15 N common 14 N MOLECULAR BIOLOGY – DNA structure, genetic code

Marshall Nirenberg a Heinrich Matthaei Cracking the genetic code MOLECULAR BIOLOGY – DNA structure, genetic code

PROMOTER AATAAA exon 1exon 2exon 3 ATG TAA AAUAAA AUG UAA AAUAAA AUG UAA intron TRANSCRIPTION Pre-mRNA mRNA DNA RNA SPLICING protein TRANSLATION coding sequence MAPSSRGG….. 5’5’3’ 3’3’5’5’ ATGAGA TACTCT ATGAGA RNA template MOLECULAR BIOLOGY – DNA structure, genetic code

600x human DNA: letters pages books 1 letter/s – reading for a century stretched DNA = 1,8m MOLECULAR BIOLOGY – DNA structure, genetic code

Bacterial DNA ~ 1 mm long ~ 1  m 1000 x more than …thanks for mobiles no more twisted telephone cords Covalently closed circular DNA SUPERCOILING MOLECULAR BIOLOGY – DNA structure, genetic code

protein scaffold Bacterial chromosome consists of about 50 giant supercoiled loops of DNA TOPOISOMERASES – enzymes that insert or remove supercoiles Type I … break only one strand -> relaxing or twisting more the helix Type II … break both strands and pass another part of the double helix through the gap MOLECULAR BIOLOGY – DNA structure, genetic code

H2A, H2B, H3, H4 200 bp 80 bp 40 bp MOLECULAR BIOLOGY – DNA structure, genetic code

Euchromatin Heterochromatin MOLECULAR BIOLOGY – DNA structure, genetic code

SECOND SUMMARY – CRUCIAL KNOWLEDGE MOLECULAR BIOLOGY – DNA structure, genetic code

T A C C G T T A G T T C A C G A T T A T G G C A A T C A A G T G C T A A ON / OFF START STOP CODING SEQUENCE REGULATORY SEQUENCE A U G G C A A U C A A G U G C U A A RNA densely packed chromosome part of the chromosome where gene X is located A U G G C A A U C A A G U G C U A A RNA TRANSKRIPTION DNA  RNA U A C Met C G U Ala U A G Ile U U C Lys A C G Ala PROTEIN tRNA according to codons brings aminoacids Met Ala IleLysAla PROPERLY FOLDED PROTEIN executes its function in cell double-strand DNA MOLECULAR BIOLOGY – DNA structure, genetic code