Exam 3 notes
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This 3 page Class Notes was uploaded by Claire on Monday April 4, 2016. The Class Notes belongs to 1320 at Texas State University taught by Professor Davenport in Spring 2016. Since its upload, it has received 14 views. For similar materials see Modern Biology 1 in Biology at Texas State University.
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Date Created: 04/04/16
RNA is AUCG single stranded DNA is ATCG double stranded Proteins do everything (hair, skin, eye) Chapter 7 focus Transcription RNA splicing Translation DNA replication Mutations How does DNA code for traits? Remember the nucleus of a cell contains its chromosomes, which are made up of DNA (and proteins) Sequences of DNA that code for a specific protein = genes Genes code for specific proteins Proteins do nearly everything, including makeup us There is a problem DNA is locked inside the nucleus Proteins are made at ribosomes and the rough endoplasmic reticulum OUTSIDE the nucleus We must have a middle man to take the information from DNA and transfer the instructions to proteins The middle man = RNA DNA RNA Proteins RNA is a nucleic acid like DNA, but differs in a few key ways Single stranded Does not contain the base T instead has the bas U GCAT CGUA Step 1: DNA RNA = transcription Step 2: RNA proteins = translation What does GCTTAG transcribe to? CGAAUC A gene has 2 kinds of segments: introns and exons Exons = truly coding nucleotides in DNA or RNA Introns = RNA splicing Immediately after transcription but before splicing we have premRNA – not spliced yet Enzymes in nucleus cut out the introns and splice together the exons to make a full strand of only coding mRNA Called finished or postmRNA Translation = mRNA proteins Remember proteins (polymers) are made of amino acids (monomers) There are 20 different amino acids Different amino acid sequence = different protein We make 11 by ourselves Have to eat 9 (essential) In transcription, 1 DNA base matches with 1 RNA base There are only 4 possible bases During translation we use an mRNA sequence to build an amino acid sequence There are only 4 RNA bases but 20 amino acids, we can’t match up 1 base with 1 amino acid We can try to match up every 2 bases of RNA to every 1 amino acid There are only 16 possible 2base combinations We’d only use 16 amino acids and have 4 extra Must use 3 bases to code for 1 amino acid Each 3 base code is called a codon Each codon specifies that a unique amino acid should be added to build the protein During translation, what amino acid sequence would the mRNA from your original gene (Q1) code for? Arginine – Isoleucine A strand of spliced postmRNA has a sequence of AUGGAAGGCCAA. Can you tell how many amino acids this codes for? Yes it would code for 4 A strand of unspliced premRNA has a sequence of AUGGAAGGCCAA. Can you tell how many are amino acids? No because the introns have not been spliced out yet A strand of unspliced premRNA has a sequence of AUGGAAGGCCAA. This particular sequence has an intron that is 3 bases long Can you tell me how many amino acids this sequence codes for? Yes, it would code for 3 DNA replication Happens in 2 main steps 1. The original double helix is pulled apart (unzipped) by the enzyme DNA helicase 2. The enzyme DNA polymerase pairs free nucleotides (A, T, G, C) with each of the now single stranded sides building new doublestranded DNA TRANSLATION USE THE CHART! DNA replication = DNA DNA (T not U) TRANSCRITION = DNA RNA (U pairs with A) Mutations Sometimes only one base changes Substitution Can cause harm to an organism Rare cases, a substitution mutation causes a benefit to an organism Some causes, a substitution mutation is completely neutral, leading to no change for the organism. This is the only one type of mutations (out of five total) that can be neutral Insertion Deletion Sometimes large pieces of DNA are moved Inversion Translocation
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