General Bio 1005
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This 3 page Class Notes was uploaded by Megan Wiggs on Wednesday October 5, 2016. The Class Notes belongs to 1005 at Virginia Polytechnic Institute and State University taught by MV lipscomb in Fall 2016. Since its upload, it has received 9 views. For similar materials see General Biology in Science at Virginia Polytechnic Institute and State University.
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Date Created: 10/05/16
nd In both prokaryotes and eukaryotes, the 2 function of DNA is to provide information needed to construct the proteins necessary so that the cell can perform all of its functions. (1 function of DNA was the replication) To do this DNA is transcribed into an mRNA molecule. The Central Dogma: DNA Encodes RNA; RNA Encodes Protein The flow of genetic information in cells from DNA to mRNA to protein is described by the central dogma, which states that genes specify the sequences of mRNAs, which in turn specify the sequences of proteins DNARNAPROTEIN DNA TO mRNA - 1 nucleotide being added to the mRNA strand for every complementary nucleotide read in the DNA strand The translation to protein is more complex because groups of 3 mRNA nucleotides correspond to 1 amino acid of the next protein sequence; however, it’s still systematic Transcription: from DNA to mRNA Prokaryotes and Eukaryotes perform the same process of transcription, with the difference of the membrane bound nucleus in eukaryotes. Eukaryotes : - NucleusmRNA transcriptcytoplasm Prokaryotes : - Occurs in cytoplasm Both 1. Initiation 2. Elongation: synthesizes new mRNA 3. Termination liberates the mRNA 1.Promoter : the DNA sequence onto which the proteins and enzymes involved in transcription bind to initiate the process - A specific sequence of DNA nucleotides - Most cases promoters exist upstream of the genes they regulate - Sequence is very important because it determines whether the corresponding gene is transcribed all of the time, some of the time, or hardly at all 2. Elongation always proceeds from one of the two DNA strands, which is called thetemplate strand enzyme called DNA polymerase 3.two kinds of termination signals: Eukaryotic RNA Processing 200 Adenine residues to the 3’ end, called the poly-A tail. Exons : protein coding sequences, a sequence present in protein-coding mRNA after completion of pre-mRNA splicing Introns: intervening sequences, removed during RNA processing, non– protein-coding intervening sequences that are spliced from mRNA during processing Splicing : process of removing introns and reconnecting exons Only finished mRNAs are exported from the nucleus to the cytoplasm Gene Expression 1: 1. What is a gene? a. A segment of DNA that contains hereditary information 2. How is information stored in DNA? a. Information is stored in the sequence of nucleotides 3. What is the relationship between genes, chromosomes, and DNA? a. Chromosomes are made of DNA (and protein) b. Genes are segments of a DNA molecule c. Each chromosome has 1 DNA molecule and hundreds of genes 4. Gene expression a. Converting genetic information into functional molecules such as RNA and proteins Genes (information and instructions for the parts) and proteins (molecular workers) related: - Beadle and Tatum o Hypothesis: Genes might encode enzymes bread mold experiment o “One gene one enzyme” = results showed a mutation in a single gene affected a single enzyme in a single biochemical pathway Modification of their hypothesis: - not all proteins are enzymes - some proteins consisit of more than 1 polypeptide - “One gene one polypeptide” - more modifications have been made 2 steps from gene to protein: 1. Transcription a. DNA RNA 2. Translation a. RNA protein The central Dogma pathway from which info flows from a DNA molecule to a functional molecule in a cell When comparing DNA and RNA adenine pairs with different bases in DNA and RNA Types of RNA 1. Messenger RNA: carries the code from DNA (in nucleus) to ribosome 2. Ribosomal RNA: makes up ribosome 3. Transfer RNA: delivers correct amino acid to the ribosome (adapters) Transcription: - DNA RNA - 3 STEPS o initiation: begins when RNA polymerase attaches to a promoter (indicates start point of where the gene is in the RNA), formation of transcription bubble= transition to elongation o Elongation: simply adding RNA nucleotides to make our RNA transcript (uracil substitutes for thymine), use template strands as instructions o Termination: Termination sequence tells RNA polymerase it’s at the end Prokaryotes have no nucleus so transcription and translation occur simultaneously Eukaryotic transcription occurs in the nucleus - Exons are need in Eukaryotic transcription (exons are spliced back together) - Eukaryotic mRNA contains introns that are removed - A 5’ and 3’cap is also added Alternative Splicing - Result: different proteins from a single gene
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