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Week 10.docx

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BIOL 111
Chin Sun

10.1 How genes work: DNA RNAprotein Learning Outcomes: 1. Differentiate between phenotype and genotype 2. Explain how the information in DNA is transformed into something we can observe. Given a DNA sequence, you will be able to write out what it is transcribed into as an mRNA and then, with a codon table, write out the resulting amino acid sequence. As well, with examples you will be able to describe how the presence of a translated protein could result in some observable characteristic (called a phenotype). Readings: Chapters 8: 197-205, 206-208 See animation here or another animation in the course vista wk10 Introductory Exercise to thinking like a geneticist: Before class describe 3 things about yourself, such as eye colour, hairy toes, dimples, or the ability to touch your knee with your chin without bending your legs, etc. Then consider whether you think these characteristics are controlled by your genes or by the environment (outside influences) or both. You have just been describing aspects of phenotype, the observable or detectable characteristics of an organism. Phenotype may be easily visible characteristics such as shape, form, colour, texture, size, or length. It could also be a biochemical property such as the ability to digest lactose or the ability to metabolize alcohol or regulate blood sugar through insulin. Phenotype could also be aspects of behaviour such as the ability of animals to make specific mating calls, the ability of plants to turn their leaves towards light. Virtually every aspect of an organism that you can describe, measure, or detect in some way is an example of its phenotype. Often completely dependent on our genetic makeup Majority of phenotype is also determined by both genetics and environment (example: skin color) Genotype is an organism’s genetic makeup, presented as the DNA sequence for a gene (or genes), that affects a particular phenotype (characteristic) of the organism. Phenotype is controlled by both genotype (inherited characteristics) and the environment. If we look around this room we will notice differences in hair colour phenotypes among individuals. If we survey the class we will find some people who can digest milk sugar and some people who are lactose intolerant, two different phenotypes. The phenotypes of human eye colour and lactose intolerance are both controlled (almost) entirely by genotype. There are differences in the DNA sequences between individuals, but how do the DNA sequence differences manifest into the characteristics we see? A gene is a specific sequence of DNA that codes for (with instruction to construct) a functional protein (only a small percentage of of genomic DNA is actually coding sequence). Difference between DNA chromosome and gene: Gene is a specific section of the DNA in the Chromosome. DNA is a chemical composition of a long molecule which contains information and instructions; it is the chemical component which carries instruction or information. When DNA condenses into a visible form under a microscope it is a chromosome. Genes are positions on DNA molecules which contain instructions to code for proteins. Chromosomes are a long string of DNA which condenses into a physical structure. DNA (gene) RNA (mRNA)  protein (mostly enzymes) DNA and RNA are composed of nucleic acids/nucleotides held together in chains FYI:RNA nucleotides are slightly different because they have an extra oxygen which DNA lacks (RNA = ribonucleic acid DNA = deoxyribonucleic acid) See Fig 8.1 in your textbook (abbreviated below) DNA must be transcribed to RNA DNA in nucleus Manufacturing of protein is in the cytoplasm RNA – messenger RNA carries information from the DNA in the nucleus to the cytoplasm to help manufacture proteins 4 nucleotides in DNA ACGT4 nucleotides in RNA ACGU Proteins are composed of amino acids held together in chains (20 types of amino acids) represented like this … but looks more like this in reality e.g., Proteins may serve as structures (e.g., microtubules, receptors on cell surfaces, keratin – the protein which makes your hair) Proteins may be involved in chemical reactions (e.g., enzymes). Enzymes are proteins that facilitate chemical reactions. Often they transform one chemical molecule into another. Proteins can be muscles (physical strength) or enzymes (biochemical reactions) Must be folded into specific shape in order to function properly—this is done with amino acids In all cases the shape of a protein is the key to its function. The shape of a protein is determined by the specific sequence of amino acids that make up the protein molecule. 1TranscriptionDNARNA It occurs in the nucleus of eukaryotic cells (or in the cytoplasm Things to remember: of prokaryotes, which do not have a nucleus); DNA is double stranded and A=T, C=G RNA is single stranded and A=U, C=GIt involves copying a segment of DNA (gene) into mRNA (messenger RNA) RNA is synthesized by using one DNA strand as a guide (template) Template T A C C A C T G strand T C C A A U G G U G A C T C C G A G G A T T G G G C T A A T A A C Non-template G A A T G G T G A G strand U A A C c mRNA transcription start site termination site DNA Regulatory region mRNA 1a. The transcription occurs when RNA polymerase (manufactures RNA in the nucleus of the cell) is able to bind to the promoter in the regulatory region. Specific proteins can bind to this region to either inhibit or activate RNA polymerase. be regulated by proteins such as repressors or activators which bind to the promoter region.nto mRNA) can Inhibitory prote
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