BIOL 201 Dr. Margulies Notes on Unit 10.1
BIOL 201 Dr. Margulies Notes on Unit 10.1 201
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This 3 page Class Notes was uploaded by Maya Lee on Sunday February 14, 2016. The Class Notes belongs to 201 at Towson University taught by Dr. Margulies in Fall 2015. Since its upload, it has received 17 views.
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Date Created: 02/14/16
Maya Lee Unit 10.1 November 12, 2015 Information Flow “The Central Dogma” DNA = Information molecule Replication= DNA copying DNA and RNA are an information containing molecule DNA can be made from DNA through the process of Replication Can transmit information from DNA to RNA through the process called transcription Transmitting RNA to DNA is called reverse transcription Information transfer into proteins is a one way street, meaning that proteins themselves do not contain real information their information is picked up from the DNA and RNA Translation = RNA Proteins or DNAProteins, once translation occurs it cannot be reversed. DNA in a Eukaryotic cell is in the Nucleus What is a “gene”? A block of DNA that encodes some kind of information Has a 5’ and 3’ end Information maybe a protein coding sequence, for example the region may give instructions for Beta Tublin gene Information for a regulatory RNA or gives information on how to make a cofactor Genomes A genome is an organisms complete set of DNA, including all of its genes. Each genome contains all of the information needed to build and maintain that organism. Genomes do not change, unless mutations occur. Mutations occur during replication or during UV radiation. The RNA transcription process takes the information that’s central in the DNA puts it somewhere else where it can be used. RNAs Five types of RNA that can be made through transcription from a gene: mRNA(messenger RNA): they code for proteins tRNA (Transfer RNA): connect to amino acids , involves ribosomes, they are a part of translation rRNA (Ribosomal RNA): also involved in translation. SnRNA (small nuclear RNA): involved in splicing. MiRNA (microRNA): involved in regulating gene expression. Questions: 1. What is a gene? A segment of DNA that codes for a protein. 2. Based on your text, what are the three phases of transcription, in order? Initiation, elongation, termination 3. Where does RNA transcription start? The promoter 4. Where does RNA transcription stop? The terminator sequence Transcription How do we make RNA from DNA? DNA polymerase makes DNA and RNA polymerase makes RNA In bacteria there’s a single RNA polymerase In Eukaryotes there are at least three RNA polymerases: RNA polymerase I transcribes the rRNA, RNA polymerase II transcribes mRNA, and RNA polymerase III transcribes tRNA, miRNA, and snRNA How each polymerase knows the gene it is going to transcribe? 5’ end region is called a promoter, this is where RNA polymerase binds because of the DNA sequence in there is attracted to RNA polymerase and there promoter sequence differs for each gene. The RNA promoters are different for RNA polymerase I, II and III. For bacteria the RNA polymerase couples with something called a sigma factor, determines specificity of which gene is going to get transcribe, allows correct promoter choice In the middle is cds (coding sequence) segment codes for protein, whatever is going to get made during transcription. The 3’ end region is called a terminator, it determines where transcription stops. RNA polymerase has no proof reading activity it cannot go back and correct if it makes a mistake Within promoters for both bacteria and eukaryotes there’s a typical sequence that is called the TATA box, a group of A’s and T’s so that we can get good separation of the DNA double strand so that we can transcribe. Transcription. and the promoter start at the TATA box There has to be a level of control over transcription There is one piece of DNA for every gene and that piece of DNA can get transcribed multiple times Control of Bacteria Transcription: The lac operon Contains genes for the breakdown of lactose, breaks down into two component sugars glucose and galactose The purpose of this break down is so they can get the glucose out of it. They need the glucose for energy. The only reason you would make the genes make the RNA from a lac operon is if you needed glucose from a lactose source. Need these genes to be on when you need glucose. One of the conditions of when this is going to happen or when the genes are going to be transcribed is when there is an absence or a low amount of glucose. When there’s no lactose the genes wouldn’t be turned on because it is a waste of energy. We need the presence of lactose to turn on the lac operon and we need an absence of glucose. Dictates when these genes are being transcribed and when they are not being transcribed. A lot of lactose and no glucose available then we need to use the lac operon to break down the lactose and use some energy. Molecular detail of how the lac operon works: Lac Z, Lac Y, and 5’P3’ structural genes) P Lac Operato The reason they are structural genes because these genes encode the enzymes required to breakdown lactose. Lac Z codes for Beta galactosidase splits lactose into the two component sugars. This genes segment is called a operon because all of the control happens in the promoter and the operator and it has multiple genes
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