1 / 45

NUCLEIC ACIDS (DNA and RNA)

NUCLEIC ACIDS (DNA and RNA). They are large, complex molecules of high molecular weight. They contain C, H, O, N and P. Their monomers are nucleotides. The Structure of a Nucleotide. Nitrogenous bases (adenine, guanine, thymine,cytosine, uracil). PO 4. 1. 3. Phosphoester bond. 2.

ronli
Download Presentation

NUCLEIC ACIDS (DNA and RNA)

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. NUCLEIC ACIDS (DNA and RNA) They are large, complex molecules of high molecular weight. They contain C, H, O, N and P. Their monomers are nucleotides.

  2. The Structure of a Nucleotide Nitrogenous bases (adenine, guanine, thymine,cytosine, uracil) PO4 1 3 Phosphoester bond 2 Glycoside bond 5C Sugar (ribose or deoxyribose) Nucleic acids are polymers of nucleotides.

  3. Nucleoside 5C Sugar Phosphate group Nitrogenous base Nucleotides + + Nucleic acids Nucleotide Adenine Guanine Adenine = Thymine Purine bases Cytosine Guanine Number of H bonds between bases Cytosine Thymine Pyrimidine bases A G A+G Purines = 1 = 1 = 1 = 1 T C T+C Pyrimidines

  4. A+G T+C 1/2 = = Number of nucleotide in DNA Number of nucleotide in DNA A+G T+C 1 = = Number of nucleotide in one strand Number of nucleotide in one strand Number of H bonds = ( A X 2 ) + ( G X 3 ) Number of H bonds = ( T X 2 ) + ( CX 3 ) = Number of phosphodiester bonds Number of nucleotide in DNA - 2 Number of nucleotide in one strand - 1 Number of phosphodiester bonds = X 2

  5. A+T G+C • ratio is specific for species. If the ratio is smaller and it is resist to heating. • In prokaryotes, DNA is found in cytoplasm and naked. In eukaryotes, histones are found in the structure of DNA. DNA is located in nucleus, mitochondrion, chloroplast. • All kind of biological process are directed by DNA. • DNA is replicated during interphase. • DNA undergoes mutations. If a mutation occurs within the sex cell, it is inherited to next generation.

  6. Nucleic Acids DNA (Deoxyribonucleic acid) RNA (Ribonucleic acid) DNA: Found in nucleus, mitochondria and chloroplast in eukaryotes Is the hereditary material that is transmitted from one generation to the next, during reproduction Contains 5 C sugar(deoxyribose), phosphate group (PO4), nitrogenous bases adenine (A) guanine (G) cytosine (C) thymine (T) DNA is double stranded (double helix)

  7. Crick and Watson walking along the Backs. 1953

  8. RNA: Found in nucleus and cytoplasm Works with DNA, involved in protein synthesis Contains 5 C sugar (ribose), phosphate group (PO4) and nitrogenous bases adenine (A) guanine (G) cytosine (C) uracil (U) RNA is single stranded.

  9. GRIFFITH’S EXPERIMENT

  10. Griffith was trying to find out a vaccine against pneumonia Blood analysis showed the presence of some live S- type bacteria transformation

  11. THE CHEMICAL BASES OF HEREDITY HERSEY AND CHASE EXPERIMENT

  12. Hersey and Chase worked with bacteriophage because it is analog of chromosome

  13. DNA REPLICATION Three possible mechanisms of DNA replication

  14. Semiconservative replication:The two parental strands seperate, each forms a template for new strand. • Conservative replication:Each of the two strands of parent DNA is replicated, without strand seperation. • Dispersive replication:During replication, parent chains break at intervals, and replicated segments are combined into strands with segments from parent chains. All daughter helixes are part old, part new.

  15. DNA REPLICATION F1 generation DNA is labelled with 15 N isotope 15 15 14 15 14 15 100% hybrid DNA Normal or 14 N compound medium F2 generation Normal or 14 N compound medium 14 15 14 15 14 14 14 14 50% hybrid DNA 15 N - 14 N 50% normal DNA 14 N - 14 N

  16. DNA REPLICATION If normal DNA is given; 2n 2 hybrid and 2 pure heavy DNA are formed If hybrid DNA is given; 2n one of the DNA is always hybrid the others are pure Replication number Replication number

  17. DNA REPLICATION MECHANISM

  18. DNA REPLICATION Replication occurs in three stages: 1. UNWINDING:Helicase enzymes seperate the parental double helix by breaking down the H bonds, forming the replication fork. Replication fork

  19. DNA REPLICATION 2. CONTINUOUS SYNTHESIS: The “leading strand” is assembled continuously in the 5' to 3' direction by DNA polymerase, using the single parental strand as a template, it adds nucleotides to the growing 3' end

  20. With okazaki fragments replication is discontinuous 3' 5' Replication is continuous 5' DNA ligase links the okazaki fragments which are 1000- 2000 nucleotide long fragments in prokaryotes and 100-300 nucleotide long in eukaryotes 3' 3' 5' C G A T 3' 5' 5' 3' 5' 3' DNA polymerase can work only in the 5' - 3' direction

  21. DNA REPLICATION 3. DISCONTINUOUS SYNTHESIS: The “lagging strand” is assembled discontinuously. It is produced as a series of short segments ( Okazaki fragments), each of which is synthesized in the 5' to 3' direction by DNA polymerase, using the single parental strand as a template

  22. OKAZAKI FRAGMENTS • In bacteria, the Okazaki fragments are each 1000-2000 nucleotides long • In eukaryotes, they are 100 to 300 nucleotides length • Finally, the fragments are joined to the 5' end of the growing chain by a DNA ligase enzyme

More Related