Nucleic Acids PDF

## Nucleic Acids - **Nucleic acids** are macromolecules that store genetic information and enable protein production. (DNA & RNA) - **Nucleotides** are monomer - **Nitrogenous bases** - Purines - Pyrimidine - **Sugar** - Ribose - Deoxyribose - **Phosphate** - Nucleotide =...

## Nucleic Acids - **Nucleic acids** are macromolecules that store genetic information and enable protein production. (DNA & RNA) - **Nucleotides** are monomer - **Nitrogenous bases** - Purines - Pyrimidine - **Sugar** - Ribose - Deoxyribose - **Phosphate** - Nucleotide = Nucleoside + Phosphate ## Chargaff's Rule - In all cellular DNAs, regardless of the species. - The number of Adenine residues is equal to the number of Thymine residues. - The number of Guanine residues is equal to the number of Cytosine residues. - Sum of Purine residues equals the sum of the Pyrimidine residues. - **A + G = T + C** ## Nucleic Acid Structure "Base Pairing" - DNA base pairing is **antiparallel** - A diagram shows a double helix of DNA with base pairs labeled: T-A, G-C, A-T, C-G. The top strand runs from 5' to 3' and the lower strand runs from 3' to 5'. - RNA (normally) exists as a single stranded polymer. - DNA exists as a double stranded polymer. - DNA double strand is created by hydrogen bonds between nucleotides. - Nucleotides always bind to complementary nucleotides. ## Polymerise Nucleotides - Nucleotides can be linked by phosphodiester linkages. - Link PO₄ at 5' end to 3' OH of next nucleotide. - A diagram shows the chemical structure of DNA and RNA. ## Nucleic Acid Structure Polymerization - The hydrophilic backbones of alternating deoxyribose and phosphate groups are on the outside of the double helix facing the surrounding water. - A diagram shows the chemical structure of the nitrogenous bases adenine, thymine and cytosine. - A diagram shows the sugar phosphate backbone, labeled "sugar phosphate backbone," with bases attached. - A diagram shows the sequence of bases labeled "TAGCAC." ## DNA is Right-handed Double Helix - DNA consists of two helical DNA chains wound around the same axis to form a right- handed double helix. - A diagram shows a model of the DNA double helix with major grooves (1) and minor grooves (2) labeled. ## The Double Helix - 3.4 Å per basepair - 10 basepairs per turn - 10-11 in aqueous solution - 2 anti-parallel strands - A diagram shows the double helix with the following measurements labeled: 3.4 Å, 36 Å, and 20 Å. ## Formation of Phosphodiester Bond - A diagram shows two nucleotide molecules forming a phosphodiester bond in a condensation reaction, releasing water. ## Where is it Located? - Most DNA is located in the cell nucleus (called **nuclear DNA**), but a small amount of DNA can also be found in the mitochondria (called **mitochondrial DNA** or **mtDNA**). - A diagram shows a DNA molecule. ## RNA - **RNA** = ribonucleic acid - **RNA** is a single-stranded polymer - Each RNA nucleotide consists of: - A pentose sugar (ribose) - A phosphate group. - A base: adenine, cytosine, guanine, uracil (instead of thymine). - A diagram shows a chain of RNA molecules ## Types of RNA - **Table 22.3. Types of RNA Molecules** | Type | Abbreviation | Percentage of Total RNA | Function of the cell | |---|---|---|---| | Ribosomal RNA | rRNA | 75 | Major component of the ribosomes | | Messenger RNA | mRNA | 5-10 | Carries information for protein synthesis from the DNA in the nucleus to the ribosomes | | Transfer RNA | tRNA | 10-15 | Brings amino acids to the ribosomes for protein synthesis | ## The Denaturation of DNA (Melting) - **Denaturation:** Double stranded DNA can be separated into two component strands in solution by increasing the temperature or pH (Alkali) - **Phosphodiester bonds** are not broken by such treatment. - **Renaturation:** Separated strands of DNA will renature when physiologic temperature and pH are achieved. ## Structural Forms of the Double Helix - There are three major structural forms of DNA: - **The B form**, described by Watson and Crick in 1953. - **The A form** - **The Z form.** ## Melting Temperature (Tm) - When DNA is heated, the temperature at which one half of the helical structure is lost is defined as the melting temperature (Tm). ## DNA Can Form Three Types of Helices - A diagram shows: - The A form. - The B form. - The Z form. - The measurements of the A form are labeled: 28Å