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Nucleic Acids What are they ? The 4th type of macromolecules The chemical link between generations The source of genetic information in chromosomes What do they do ? Dictate amino-acid sequence in proteins Give information to chromosomes, which is then passed from parent to offspring What are they made of ? • Simple units called nucleotides, connected in long chains • Nucleotides have 3 parts: 1- 5-Carbon sugar (pentose) 2- Nitrogen containing base (made of C, H and N) 3- A phosphate group ( P ) • The P groups make the links that unite the sugars (hence a “sugarphosphate backbone” Nucleic Acids 1. Are the genetic material 2. DNA = Deoxyribonucleic acid 3. RNA = Ribonucleic acid 4. Are polymers of nucleotides 5. A nucleotide consists of three parts : - a pentose(5C-sugar) - a phosphate - a nitrogenous base Types of N.A. (depending on the sugar they contain) 1- Ribonucleic acids (RNA) The pentose sugar is Ribose (has a hydroxyl group in the 2nd carbon---OH) 2- Deoxyribonucleic acids (DNA) The pentose sugar is Deoxyribose (has just an hydrogen in the same place-H) Deoxy = “minus oxygen” MICROMOLECULE: (monomer) Nucleotide MACROMOLECULE: (polymer) Nucleic acid 1. RNA 2. DNA Anatomy of Nucleotide I. Phosphate group (always the same): O OH P O~ OH OR P II. SUGAR=5 CARBON (PENTOSE) A. RIBOSE (USED IN RNA) B. DEOXYRIBOSE (USED IN DNA) -OH REMOVED AT CARBON 2’ O O 1’ 1’ 2’ OH OH RIBOSE 2’ OH DEOXYRIBOSE III. BASES 1. 2. 3. 4. 5. ADENINE GUANINE THYMINE CYTOSINE URACIL PURINES (Double Ring) PYRIMIDINES (Single Ring) Nitrogenous Bases 1. Compounds that contain nitrogen 2. Two types: - pyrimidines (single ring bases) - purines (double ring bases) PYRIMIDINES PURINES COMBINATIONS OF FIVE DIFFERENT BASES • DNA USES THYMINE* GUANINE CYTOSINE ADENINE BASE PAIRS T+A=2 H-BONDS G+C=3 H-BONDS • RNA USES URACIL* GUANINE CYTOSINE ADENINE BASE PAIRS U+A=2 H-BONDS G+C=3 H-BONDS Single-strand of a Nucleic Acid 1. Consist of a polymer of nucleotides. 2. Joined by phosphodiester linkages. P A T G S P S P S C P S P Double-stranded DNA 1. Will be discussed in detail later in the course GENETICS. (TWISTED LADDER=DOUBLE HELIX) 2. DNA=2 CHAINS OF NUCLEOTIDES SIDE BY SIDE H-BONDED TOGETHER AT BASES The Double Helix (DNA) Structural model: • Model proposed by Watson & Crick, 1953 • Two sugar-phosphate strands, next to each other, but running in opposite directions. • Specific Hydrogen bonds occur among bases from one chain to the other: A---T , C---G Due to this specificity, a certain base on one strand indicates a certain base in the other. • The 2 strands intertwine, forming a doublehelix that winds around a central axis Chargraff’s Rule: • Adenine and Thymine always join together A T • Cytosine and Guanine always join together C G 16 DNA Nucleotides Composition (3 parts): 1- Deoxyribose sugar (no O in 2Nd carbon) 2- Phosphate group 3- One of 4 types of bases (all containing nitrogen): - Adenine - Thymine (Only in DNA) - Cytosine - Guanine How DNA Works 1- DNA stores genetic information in segments called genes 2- The DNA code is in Triplet Codons (short sequences of 3 nucleotides each) 3- Certain codons are translated by the cell into certain Amino acids. 4. Thus, the sequence of nucleotides in DNA indicate a sequence of Amino acids (Primary Structure) in a protein. RNA Nucleotides Composition ( 3 parts): 1- Ribose sugar (with O in 2’carbon) 2- Phosphate group 3- One of 4 types of bases (all containing nitrogen): - Adenine - Uracil (only in RNA) - Cytosine - Guanine DNA vs RNA • DNA 1- Deoxyribose sugar 2- Bases: Adenine, Thymine, Cytosine, Guanine 3- Double-stranded helix arrangement • RNA 1- Ribose sugar 2- Bases: Adenine, Uracil, Cytosine, Guanine 3- Single stranded How does DNA make a Protein? • Transcription - RNA is made from DNA • Translation - Proteins are made from the message on the RNA DNA->transcription->RNA->translation->protein • Messenger RNA (mRNA) is the blueprint for construction of a protein. • Ribosomal RNA (rRNA) is the construction site where the protein is made. • Transfer RNA (tRNA) is the truck delivering the proper amino acid to the site at the right time. ATP 1. Adenosine triphosphate 2. Is a nucleotide. 3. Involved with energy currency of the cell. 4. MOST IMPORTANT NUCLEOTIDE THE ENERGY TRANSFER MOLECULE MONEY OF ALL LIVING THINGS 5. 3 PHOSPHATES-RIBOSE SUGAR-ADENINE BASE ATP/ADP/AMP—LIKE NICAD(battery) THEY CAN BE RECHARGED ENERGY + P + P ATP FULLY CHARGED AMP RUN DOWN P ADP PARTIAL CHARGE P MITOCHONHDRIA IS THE RECHARGER-THEY ADD PHOSPHATES BACK ON OTHER INFO: • • • NAD &FAD ARE ALSO NUCLEOTIDES (COENZYMES) Review of NUCLEIC ACIDS MACROMOLECULES • • • • • RNA=RIBONUCLEIC ACID DNA=DEOXYRIBONUCLEIC ACID LONG CHAINS OF NUCLEOTIDES HOOKED TOGETHER BY CONDENSATION REACTIONS. DNA=MILLIONS OF NUCLEOTIDES RNA=millions but shorter than DNA(piece of dna)