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Lecture 7

BIO206 Lecture 7 Chapter 7.pdf

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Department
Biology
Course
BIO206H5
Professor
George S Espie
Semester
Fall

Description
Lecture 7/ Chapter 7 September-23-13 10:15 PM Genetic Information (genotype) stored in DNA • Encoded as the linear sequence of nucleotides • Primary structure of proteins encoded as primary structure of DNA • Different sequences convey different information • All cells use the same 4 deoxyribonucleotidesAT GC to encode genetic information - 4 bases in each type (substitution of thymine for uracil in RNA) - sugar is ribose not deoxyribose - hydroxyl group extra Structure of DNA provides a mechanism for heredity - Genome - completeset of information in organism's DNA Eukaryotes:located in nucleus, mitochondria & chloroplast - segregated Prokaryotes:nucleoid - integrated + plasmids A gene is • A region (or regions) of DNA which controls a discrete hereditary trait or characteristic of an organism, usually responsible for specifying the primary structure of an RNA moleculeand protein • … it usually corresponds to a single protein or RNA molecule • Genes are arranged along the chromosomes • A physical & functional unit of heredity, which carries information from one generation to the next. • In molecular terms, it is the entire DNA sequence necessary for the production of a functional protein or RNA molecule • It is a name given to a segment of DNA that codes for a protein or for an RNA moleculethat has a function in an organism • (usually) discrete non-overlapping entities ○ Exception:viruses have very small genome. In order to maximize coding capacity, they need to make best use of space available Basic anatomy of a gene • Contains a nucleotide sequence which when finally translated forms a protein (or RNA molecule). • Signals for “start” & “stop” translation • DNA is not directly translated … a message is made containing the information for a trait (RNA moleculeis an intermediate) • Signals to identify where to “start” & “stop” transcription of the message: (not the same as start & stop of translation) • Switches to determine when and when not to transcribe DNA • A means to identify which DNA strand should be transcribed • ATG – methionine(start codon) • ATG – methionine(start codon) Genes are not easy to find in the genome • They have a “start” (promoter) • They have a “stop” (terminator) • They have a region of DNA between the “start” and the “stop” • Part of the gene is transcribed • Contain an “open reading frame”,an ORF • Need to identify these regions How many genes in a genome? Gene density goes down as genome gets moresophisticated Network of regulators gets much more complicated A Prokaryotic Gene includes • Promoter:A region of a gene to which RNA polymerasebinds to begin transcription (non- coding start) • Exon: A region of a gene that is transcribed to RNA and encodes part or all of a protein • UTRs: Regions of a gene that are transcribed, but not translated, which contain control elements. 5’ & 3’ UnTranslated Regions Prokaryotic genes usually lack introns A Eukaryotic Gene includes • Exon : A region of a gene that is transcibed to RNA and encodes part or all of a protein • Introns: A region of a eukaryoticgene that does not code for protein, but is transcribed to RNA & later excised. (intervening sequences between exons) • Promoter:A region of a gene to which RNA polymerasebinds to begin transcription (non- coding start) • UTRs: Regions of a gene that are transcribed, but not translated, which contain control elements. 5’ & 3’ UnTranslated Regions Eukaryotic vs. Prokaryotic genes TypicalEukaryotic gene Promotercan extend into transcribed region Enhancers – control the regulation of the gene are placed before the promotersite Termination of transcription is hard to determine in Eu but e
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