Gene Expression AECC Handout PDF

Gene expression Deoxyribonucleic Acid (DNA) Protein  Learning Outcomes Name and describe the component parts of DNA Understand the role and significance of codons in the transfer of genetic information Identify mRNA, tRNA and rRNA and describe their functions Describe the location an...

Gene expression Deoxyribonucleic Acid (DNA) Protein  Learning Outcomes Name and describe the component parts of DNA Understand the role and significance of codons in the transfer of genetic information Identify mRNA, tRNA and rRNA and describe their functions Describe the location and process of transcription Understand the role of particular base sequences in transcription control Describe the locations and process of translation DNA & RNA belong to a major group of biomolecules monosaccharides Organic bases Amino acids Fatty acids Glycerol nucleotides polyssaccharides Nucleic acids Proteins Lipids  Nucleic Acids are polynucleotides Genetic material Ability to carry N-glycosidic instructions bond Ability to be copied (perfectly, repeatedly) Phosphate Pentose Nitrogen group sugar containing base Ribose Adenine (A) DNA base pairing rules: Thymine (T) Deoxy_ A-T ribose Guanine (G) C-G Cytosine (C) Uracil (U) nucleotide nucleoside DNA is a polynucleotide This diagram shows the polymerisation of two nucleotides Phosphodiester bond Nb. This is a covalent bond  RNA COMPARED WITH DNA RNA is single stranded, not double stranded like DNA RNA is short, only 1 gene long, where DNA is very long and contains many genes RNA uses the sugar ribose instead of deoxyribose in DNA RNA uses the base uracil (U) instead of thymine (T) in DNA RNA cannot form stable double helices  Types of RNA Three main types of RNA mRNA – carries information specifying the amino acid sequences from DNA to ribosomes rRNA - structural or catalytic (enzyme – ribozyme) roles in ribosomes tRNA – binds amino acid molecules dependant on the three base code it is carrying This is effectively the interpreter in the translation rRNA  Gene Expression The information content of DNA is in the form of specific sequences of nucleotides along the DNA strands. The DNA inherited by an organism leads to specific traits by dictating the synthesis of specific proteins Single point mutation can cause significant medical conditions in humans Example: Sickle-Cell Anaemia Fatigue and Anaemia. Pain Crises. Dactylitis (swelling and inflammation of the hands and/or feet) and Arthritis. Bacterial Infections. Splenic Sequestration (sudden pooling of blood in the spleen) and Liver Congestion. Lung and Heart Injury. Leg Ulcers. Sickle-cell disease is caused by a single point mutation (a missense mutation) in the beta-haemoglobin gene The missense mutation cause one GAG codon to be turned into GUG The result is the amino acid valine is added to the protein instead of glutamic acid. Gene expression can be divided into two stages, called transcription and translation Transcription and Translation Cells are governed by a cellular chain of command DNA RNA protein Transcription Is the synthesis of RNA under the direction of DNA Produces messenger RNA (mRNA) Translation Is the actual synthesis of a polypeptide, which occurs under the direction of mRNA Occurs on ribosomes Chromatin is approx.: 30% DNA 60% histones 10% RNA Chromosomes, visible as little X shapes in the nucleus during mitosis, are very long strands of DNA compacted by being wound round …………….. molecules called histones and then coiled up. Marieb & Hoehn, 2018 Transcription and Translation In a eukaryotic cell the nuclear envelope separates transcription from translation Extensive RNA processing occurs in the nucleus Nuclear envelope The nucleus provides a DNA separate compartment for TRANSCRIPTION transcription. Pre-mRNA RNA PROCESSING mRNA The original RNA transcript, called pre-mRNA, is Ribosome processed before leaving TRANSLATION the nucleus as mRNA. Polypeptide Marieb & Hoehn, 2018  Transcription Transcription is the synthesis of RNA from DNA The RNA is a template of the relevant genetic code for the protein that will be made RNA polymerase is the catalyst The enzyme opens the DNA strands and inserts the new RNA nucleotides Base pairing rules are the same as DNA, except that in RNA, uracil substitutes for thymine Transcription Marieb & Hoehn, 2018  Transcriptional control Gene expression is controlled at the transcription stage An example of transcriptional regulation would be controlling the rate of gene transcription by helping or hindering RNA polymerase binding to DNA The many mechanisms are clustered according to the part of the process they can influence so they are linked to Initiation, Elongation and Termination