BIO 344 1st Edition Lecture 1 Outline of Last Lecture I. First Day of Class- SyllabusOutline of Current Lecture I. Genome Structurea. Comparison of Bacteria and HumanII. Bacterial Genomea. Open reading framesb. Trp operonIII. Human GenomeIV. DNA StructureCurrent LectureI. Genome Structure- Organization of genetic information- Bacteria have circular and singular genome, one origin of replication, high density coding sequence, close physical proximity between genes that are functionally related- Humans have multiple and linear genome, multiple origins of replication, lower density of coding sequence, genes that are functionally related are not necessarily in close proximity- Number of genes does not correlate to organism complexityII. Bacterial Genome- Coding sequence predominates over intergenic and noncoding sequenceThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Open reading frames (orf)= frame of base pairs, starting with a start codon, that could potentially code for a gene- Non protein coding genes= regulatory genes that code for tRNAo Start codon= AUG, ATGo Genes in one orf code for one protein- Remember that there are several ways to read sequenceo You can read either strand (5’->3’), and there are different reading frames depending on which strand is read and placement of start codons- Dense with coding sequence—very efficiento Not many non protein coding genes between protein coding sequenceso Functionally related genes are typically together- Can synthesize all amino acids- Trp operono Operon= a unit made up of linked genes that regulates other genes responsible for protein synthesis Coordination of regulation and transcription, efficient, and portableo Trp operon= controls transcription of tryptophan Regulated by trp repressor- Trans acting factor- Represses via negative feedback systemo Trp synthesis is on until it reaches a certain concentration, and the trp repressor will turn off transcription by blocking promoters from binding to transcription site- Regulon= Represses itself, the trp operon, and also aroL (aromatic aa biosynthesis), aroH (aromatic aa biosynthesis), and mtr (tryptophan permease)o Polycistronic mRNA= carries several orfs each of which is translated into a polypeptideo Horizontal gene transfer= operons allow transcription gene units to be transferred from one organism to another Vertical= parent offspringo Restriction enzyme= enzyme that cleaves DNA at a specific locus of sequenceIII. Human Genome- 23 base pairs, about 3.2* 10^9 base pair combinations- 30,000-50,000 origins of replication- Epigenetics= modifications to the genome that do not involve a change in the nucleotide sequence, i.e. changes in chromatin structure for regulation or transcription- Humans have only 5 times more genes than bacteria and less than 2 times more than a fruit flyo Basic cellular processes require about the same number of genes Metabolically, humans are not so complex when compared to bacteriaand yeast- Low gene densityo About one gene is coded in a 12,000 base pair sequence to bacteria’s eight genes coded in a sequence of the same length- Genes are not organized by function- Transcription factors are combinationalo Multiple are used togetherIV. DNA Structure- Antiparallel, polarity 5’3’- Chemical forces that hold it together can be revealed by what denatures ito Heat or rise in pH Rise in pH breaks hydrogen bonds and replaces with –OH groupso DNA bases are stacked and held together with Hydrogen bonding between edges of baseso Guanine and cytosine are more stable with 3 hydrogen bonds (vs. 2 hydrogenbonds in adenine and thymine) - The ends of DNA “breathe”o Less stable here so enzymes try to denature strands here- Overall geometry of base pairs from edge to edge down the helices is invariableo Polymerase recognizes this general shape to identify DNA for transcription initiationo Enzymes have trouble differentiating sequence because of
View Full Document
Unlocking...