BCHM 4116 1st Edition Lecture 4 Outline of Last Lecture I Watson and Crick base pairing II What is DNA helix stabilized by III 3 types of DNA IV Biological Implications of double stranded helix in DNA V Intercalating Agents VI Structural Transitions of DNA VII Hyperchromic shift VIII DNA structure is dynamic IX Tertiary structure of DNA X L T W XI Organization chromatin and chromosome Outline of Current Lecture I The Secondary and Tertiary Structures of RNA II tRNA III Physical structure of genes in eukaryotes IV Genome size correlates with biological complexity Current Lecture Order of bases are not that conserved however you find that the way it folds is highly conserved This is what s helpful for epigenetic analysis tRNA use it as an example of how a single stranded molecule unlike DNA can take on a particular secondary or tertiary structure This is a tRNA isolated from yeast and its job is to bring the phenylalanine to the ribosome during protein synthesis This is the sequence of the tRNA from 5 to 3 1 This is a secondary structure a Intrastrand strand base pairing helps the stability of the structure GC pair and GU pair which can hydrogen bond 2 There exist modifications to the nucleotides a D dihydrouridine a reduced form of uridine b Pseudouridine These 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 i Normally Uracil is linked to ribose through a N glyosidic bond ii In this instead of the nitrogen connecting it a C is connecting it to the ribose iii This modification is through to be helping with the structure stability c m i The base is methylated at the position indicated as a superscript 1 Ex Cm5 the cytosine is methylated at position 5 RNA At the 3 end there is CAA OH This 3 hydroxyl is where an ester will form with the amino acid On top of the secondary structure there is a tertiary structure which is also intrastrand interactions pink lines Gene Gene genes are the units carrying and transferring inherited characteristics from parents to offspring A gene commonly is defined as the entire DNA segment that is necessary for the synthesis of a functional RNA and or polypeptide Polycystronic one mRNA can encode for multiple proteins 1 5 UTR 3 UTR Exon section that made it into the mature mRNA Exons extend all the way to the 5 and 3 ends and include the UTR untranslated region The gene doesn t exist just from the start and stop codon but includes the 5 and 3 untranslated regions UTR because they also make it into the mature mRNA Upstream of the transcription start site is labeled 1 Transcription start is different from the translation start site The translation start is from ATG to stop codon Transcription start is different from translation start Always a distance from the transcription start and translation start Poly A tail it is the feature of the mRNA not the gene It signals the stop for transcription Stop codon signals the stop for translation Genome and Genome Organization Genome Entire set of genetic material in an organism This is the chromosomal DNA and mitochondrial DNA Size variation Even though there is an increase in genes from bacteria to complex mammals this increase in genes doesn t hold within a taxa All organisms in a taxa have about the same number of genes Size of genome varies between taxonomic groups Size of genome doesn t vary much within taxonomic groups Why such great variation Repetitive sequences may exist that bulk up the genome This occurs in polyploid organisms Question to think about Is there is a strict correlation between genome size and biological complexity Worms 19000 genes and humans 20000 genes have a difference of about only 1000 genes Genes just move around we can do much more so why do worms and humans have about the same number of genes