Nucleic acids

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Transcript of Nucleic acids

  • 1.Nucleic Acids DNA and RNA

2. Hundreds of thousands of proteins exist inside each one of us to help carry out our daily functions. These proteins are produced locally, assembled piece-by-piece to exact specifications 3. This information, detailing the specific structure of the proteins inside of our bodies, is stored in a set of molecules called nucleic acids. 4. Nucleic Acids DNA and RNA

  • DNA - deoxyribonucleic acid
  • RNA - ribonucleic acid
  • DNA- stores genetic information
  • RNA - use in protein synthesis
  • for putting genetic information


  • Nucleic Acids are POLYMERS
  • Proteins are polypeptides,
  • Carbohydrates are polysaccharides
  • Nucleic acid is polynucleotide- made of

6. Structure of NUCLEOTIDE

  • The deoxyribonucleic acid, DNA, is a long chain of nucleotides which consist of
        • Deoxyribose (a pentose = sugar with 5 carbons)
        • Phosphoric Acid
        • Organic (nitrogenous) bases (Purines - Adenine and Guanine, or Pyrimidines -Cytosine and Thymine

7. The Structure of Nucleic Acid

  • Nucleic Acid is a polymer of nucleotides
  • It is a very large molecule that have two main parts. The backbone of a nucleic acid is made of alternating sugar and phosphate molecules bonded together in a long chainphosphodiesterbonds.
  • Each of the sugar groups in the backbone is attached (via the bond shown in blue) to a third type of molecule called a nucleotide base.

8. 9. The Structure of Nucleic Acids

  • The phosphodiester bonds link the 3' carbon in the sugar ring of one nucleotide to the 5' carbon on the next nucleotide
  • sequence of bases constitutes the genetic information

10. Different pentose sugars in RNA & DNA RNA DNA Sugar carbons haveprime numbers,to distinguish them from atoms in bases 11. Nucleotides

  • Deoxyribonucleotides
  • Ribonucleotides

12. Heterocyclic Nitrogen Bases RNA DNA 13. DNA - POLYNUCLEOTIDE




15. Structure of Nucleic Acid

  • Only four different nucleotide bases can occur in a
  • nucleic acid, each nucleic acid contains millions of
  • bases bonded to it.
  • The order in which these nucleotide appear in the
  • nucleic is the coding for the information carried in
  • the molecule.
  • In other words, the nucleotide serve
  • as a sort of genetic alphabet onwhich the structure of each proteinin our bodies is encoded .

16. DNA

  • In the early 1950s, four scientists, James Watson and Francis Crick at Cambridge University and Maurice Wilkins and Rosalind Franklin at King's College, determined the true structure of DNA from data and X-ray pictures of the molecule that Franklin had taken. In 1953, Watson and Crick published a paper in the scientific journalNaturedescribing this research. Watson, Crick, Wilkins and Franklin had shown that not only is the DNA molecule double-stranded, but the two strands wrap around each other forming a coil, or helix.

17. WATSON-CRICK MODEL Combination of two single strands The Double Helix Sugar-phosphate backbone outside,bases inside 1953 18. WATSON-CRICK MODEL Bases formspecific base pairs , held togetherby hydrogen bonds Structure compatible with any sequence of bases 19. WATSON-CRICK MODEL

  • The nucleotide bases of the
  • DNAmolecule form
  • complementary pairs :
  • adeninealways bonds tothymine
  • (and vice versa)
  • andguaninealways bonds tocytosine
  • (and vice versa).
  • This bonding occurs across
  • the molecule, leading to a
  • double-stranded system

20. The base pairing is the key to understanding how DNA functions

  • As a trick for remembering how the bases pair up (if symbols are arranged in alphabetical order):
  • ACGT
  • AdenineCytosineGuanineThymine

21. Watson-Crick base pairs Hydrogen bonds are weaker than covalent bonds (eg. C-C or C-N) Covalent bonds determine structure, Weak hydrogen bonds -Stabilize double helix 22. Base Pairing in DNA

  • DNA samples from different cells of the same species have the same proportions of the four heterocyclic bases
  • DNAsamples from different species have different proportions of bases
  • Human DNA contains:
  • 30% - Adenineequal amounts
  • 30% - ThymineA = T
  • 20% - Guanine equal amounts
  • 20% - Cytosine G = C
  • The bases occur in pairs!!!

23. DNA replication

  • The double-stranded DNA molecule has
  • the unique ability that it can make exact
  • copies of itself, or self-replicate. When
  • more DNA is required by an organism
  • (such as during reproduction or cell
  • growth) the hydrogen bonds between the
  • nucleotide bases break and the two
  • single strands of DNA separate. New
  • complementary basesare brought in by
  • the cell and paired up with each of the
  • two separate strands, thus forming two
  • new, identical, double-stranded DNA
  • molecules.

24. DNA

  • The blueprint for the structure and functioning of our bodies is contained in the genetic material found in the nucleus.
  • The total number of base pairs in a human cell the HUMAN GENOME is 3 billion base pairs
  • The genetic material (chromatin) is composed of DNA (Deoxyribonucleic acid) and protein
  • Whena cell is not actively dividing, its nucleus is occupied by CROMATIN


  • Chromatin is DNA wound tightly around proteins called histones.
  • During cell division, chromatin organizes itself into CHROMOSOMES
  • Each chromosome contain a different DNA molecule!!!

26. It is a linear strand of DNA in combination with nuclear proteins We refer to this complex of DNA andproteins aschromatin It is a linear arrayof genes As a set - they areour genome What is a chromosome? 27. CHROMOSOME

  • Organisms differ in their number of chromosomes
  • 64 chromosomes - 32 pairs
  • 38 chromosomes - 19 pairs
  • 6 chromosomes - 3 pairs
  • 46 chromosomes - 23 pairs

Heredity is encoded in DNA within the chromosomes 28.

  • During cell division the DNA is duplicated so that each new cell receives a completecopy
  • Each DNA molecule is made up of many GENES
  • GENE is individual segment of DNA that contains the instructions that direct the synthesis of a single polypeptide

What is a GENE? 29. RNA

  • Ribonucleic acid, or RNA, gets its name from the
  • sugar group in the molecule's backbone - ribose.
  • Several important similarities and differences
  • exist between RNA and DNA.

30. DNA vs RNA

  • DNA consists of two associated polynucleotide strands that wind together in a helical fashion. It is often described as a double helix
  • Most RNA is single stranded and does not form a double helix

31. DNA vs RNA

  • DNA Composition
  • Deoxyribose(a pentose = sugar with 5 carbons)
  • Phosphoric Acid
  • Organic (nitrogenous) bases:
  • (Purines - Adenine and Guanine, or Pyrimidines -Cytosine andThymine )
  • RNA Composition
  • Ribose(a pentose = sugar with 5 carbons)
  • Phosphoric Acid
  • Organic (nitrogenous) bases:
  • Purines (Adenine and Guanine) and Pyrimidines (Cytosine andUracil )

32. DNA vs RNA

  • DNA Composition
  • The base composition is variable, but in all cases the amount of adenine is equal to the amount of thymine (A=T).
  • In the same manner,C=G.
  • Consequently
  • A+C = T+G
  • RNA Composition
  • because most RNA is single stranded and does not form a double helix

33. RNA

  • RNA (ribonucleic acid) is the messenger of DNA within the cell.
  • Forms of RNA direct the cell to manufacture specific enzymes and other proteins
  • There are several different kinds of RNA made by the cell:
    • mRNA-messenger RNA