1 / 46

Major Events in Genetics

Explore the major events in the field of genetics, including the discovery of genes and DNA, the role of genetic material in determining traits, and the structure and properties of DNA. Discover how genetic material is organized in prokaryotes and eukaryotes, and the importance of chromatin in gene expression.

gerardoa
Download Presentation

Major Events in Genetics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Major Events in Genetics

  2. A gene is a genetic sequence that codes for an RNA. In protein coding genes, the RNA codes for a protein. A gene is a coding unit

  3. DNA is the genetic material of bacteria, viruses and animal cellsHow was this discovered?

  4. 1870: DNA (nuclein) was first isolated from the nuclei of lymphocytes by F. Miescher. Alkali extraction.

  5. 1909: The T. Morgan Drosophila experiments led to the chromosomal theory of heredity.The word “gene” is first introduced

  6. Sex-linked transmission

  7. White eyes Red eyes White eyes Red eyes F1 100% Red eyes 100%White eyes X X F1 100% Red eyes F2 100%Red eyes 50% Red eyes 50%White eyes F2 50% Red eyes 50%White eyes 50% Red eyes 50%White eyes

  8. The bacterium Pneumoccocus kills mice by causing pneumonia Pneumoccocus virulence is determined by its capsular polysacharide component of cell surface allows the bacteria to escape destruction by the host. Several types of pneumoccocus have different types of polysacharides. Two groups S (smooth) and R (rough) GRIFFITH

  9. GRIFFITH 1928

  10. The transforming Principle is DNA • Some properties from dead S-type bacteria can transform the live R-type bacteria and render it virulent (S-type)

  11. What is the chemical nature of the transforming factor ? Avery, MacLeod e McCarty Only DNase destroyed the transforming factor.

  12. Bacteriophage

  13. Bacteriophages attacking a bacteria

  14. Alfred Hershey and Martha Chase • Performed experiments showing that DNA is the genetic material of a phage known as T2 • Used radioactive isotopes for labeling • Sulfur isotope, 39S, to label the protein • Phosphorous isotope, 32P, to label the DNA

  15. HERSHEY e CHASE Protein labelling: No radioactivity in progeny DNA labelling: radioactivity in progeny

  16. 1950 The Chargaff RULES • - The number of guanines and adenines equal the number of cytosines and thymines. • - The relative amounts of the G/C and A/T vary among different species.

  17. X ray diffraction allows to obtain information on the three dimensional structure of molecules.

  18. Rosalind Franklin and Maurice Wilkins • They were using a technique called X-ray crystallography to study molecular structure • Rosalind Franklin • Produced a picture of the DNA molecule using this technique • Already determined that the sugar-phosphate ladder was on the outside of the molecule • Wilkins received Nobel Prize in 1962 • Franklin –and Chargaff- did not.

  19. James Watson and Frances Crick • Watson and Crick published an article in the same Nature issue as Wilkins and Franklin in April 1953 that DNA was a double helix through observations of the X-ray crystallographic images of DNA • Watson and Crick reasoned that there must be additional specificity of pairing • Dictated by the structure of the bases • Each base pair forms a different number of hydrogen bonds • Adenine and thymine form two bonds, cytosine and guanine form three bonds

  20. Race to the structure

  21. A B Z

  22. A-DNA e B-DNA: Doppie eliche destrorse che portano rispettivamente 10,9 e 10 coppie di basi per giro completo dell’elica. Nella cellula il DNA si trova tipicamente come forma B, la forma A si riscontra solo in condizioni di umidità relativamente bassa.

  23. Z-DNA: Elica sinistrorsa con 12 paia di basi per ogni giro completo dell’elica. Elica sottile ed allungata con solco minore profondo e solco maggiore poco evidente. Associato a particolari sequenze di basi, come basi puriniche che si alternano a basi pirimidiniche.

  24. Properties of the geneticmaterial: • Potentiallyitcontains a hugeamount of information • The information can be translated in a phenotype. • The information can be copied in a faithfullmanner

  25. Specific structures of RNA

  26. Cromosomes of prokaryotes -single chromosome of circular double stranded DNA -in some cases, a major chromosome and severalmuchsmallerchromosomes (plasmids) Organizedas NUCLEOID of supercoiled DNA

  27. Eukaryoticchromosomes -Organized in chromatinwith histonic and non histonicproteins

  28. DNA domain organizedasloopsbound to a structureslinked to the nuclear membrane = NUCLEAR MATRIX. • DNA sequencesassociated to the nuclearmatrix = MAR (matrix attachment regions). • -MAR are generallyassociated to regionsactive in transcription and earlyreplication.

  29. Chromatin: -constitutive and facultativeheterochromatin -euchromatin

More Related