BCH1001 Macromolecules 4 - Nucleic Acids PDF

Biochemistry & Cell Biology BCH1001 Macromolecules 4 – Nucleic Acids Dr Patricia Johnson [email protected]  NUCLEIC ACIDS Nucleic acids are the information storage devices of the cell They are polymers of nucleotides 2 varieties- DNA deoxyribonu...

Biochemistry & Cell Biology BCH1001 Macromolecules 4 – Nucleic Acids Dr Patricia Johnson [email protected]  NUCLEIC ACIDS Nucleic acids are the information storage devices of the cell They are polymers of nucleotides 2 varieties- DNA deoxyribonucleic acid RNA ribonucleic acid Functions: DNA is the basic hereditary material in all cells and contains all the information necessary to make proteins DNA serves as the template for the synthesis of RNA Central Dogma of Genetics Why would the cell want to have an intermediate between DNA and the proteins it encodes?  The DNA can then stay pristine and protected, away from the caustic chemistry of the cytoplasm  Gene information can be amplified by having many copies of an RNA made from one copy of DNA  Regulation of gene expression can be effected by having specific controls at each element of the pathway between DNA and proteins. The more elements there are in the pathway, the more opportunities there are to control it in different circumstances Nucleic Acids (One sub-unit of DNA or RNA) A nucleic acid is a polymer of nucleotides that are each composed of a phosphate group, a sugar, and a nitrogenous base, The sugar is ribose in ribonucleotides and deoxyribose in deoxyribonucleotides. There are two groups of nitrogenous bases: Purines (adenine, guanine) and Pyrimidines (cytosine, uracil, and thymine). U is found only in ribonucleotides, and T is found only in deoxyribonucleotides. Structure Each nucleotide consists of 3 components- 1) 5-carbon sugar 2) a phosphate group 3) an organic nitrogen-containing base Why is DNA important? DNA is hereditary material which determines who we are : inherit from our parents and pass onto our children DNA is located within the nucleus Each cell contains 3 x 109 bases which is coiled up tightly in the cell Each cell contains over 1 metre of DNA DNA is arranged into chromosomes : 46 or 23 pairs : 23 from each parent Chromosome are made up of genes : each gene codes for a different protein Loss or mutation of genes results in disease  Building blocks of DNA DNA is a double helix made up of sugar, phosphate and bases - resembles a twisted ladder Sugar in DNA is deoxyribose Bases are Purines : Adenine (A) and Guanine (G) Pyrimidine : Cytosine (C) and Thymine (T) A pairs with T and G pairs with C Structure determined in 1953 by Watson and Crick  Structure of DNA - helix DNA : base Sugar and phosphate make up sides and bases make up rungs of ladder pairing DNA Is a Double Helix Cartoon of base pairing Cartoon of double helix Chromosome and Genes Chromosomes are made up of thousands of genes Each gene makes protein which has a specific function in cell (allele) Each gene has specific location called gene loci Human Genome Project : now know complete sequence of Karyotype – 46 chromosomes DNA replication –for cell division to occur Transcription -The process of making a RNA strand using a DNA template RNA is similar to DNA (contains sugar, phosphate and bases) BUT is single stranded RNA also contains the base uracil instead of thymine Cells contain 3 different types of RNA Messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA) DNA is transcribed into messenger RNA (mRNA) in nucleus by transcription DNA unwinds and acts as template for RNA Enzyme RNA polymerase determines the correct strand of DNA to use and the direction Nucleotide structure of RNA There are several different kinds of RNA made by the cell mRNA - messenger RNA is a copy of a gene. It acts as a photocpoy of a gene by having a sequence complementary to one strand of the DNA and identical to the other strand. The mRNA carries the information stored in the DNA in the nucleus to the cytoplasm where the ribosomes can make it into protein. tRNA - transfer RNA is a small RNA that has a very specific structure such that it can bind an amino acid at one end, and mRNA at the other end. It acts as an adaptor to carry the amino acid elements of a protein to the appropriate place as coded for by the mRNA. rRNA - ribosomal RNA is one of the structural components of the ribosome. It has sequence complementary to regions of the mRNA so that the ribosome knows where to bind to an mRNA it needs to Translation- The process of protein synthesis mRNA leaves nucleus and goes to cytoplasm to make protein using transfer RNA (tRNA) and ribosomal RNA (rRNA) A polypeptide is produced Overview of Transcription and Translation Summary Of Nucleic Acids https://www.youtube.com/watch? v=JQByjprj_mA Some useful links for Macromolecules… http://www.youtube.com/watch?v=f4Gicf7ONGA (Carbohydrates and Lipids) http://www.youtube.com/watch?v=lDUk7_dfNSQ (Nucleic Acids and Proteins)