BIOL 152 Bulluck Lecture 1 Gene:- The gene states the characteristics of an organism- Region of DNA whose final product is either a polypeptide or an RNA moleculeProteins:- Proteins are the link between genotype and phenotypeGene expression:- Process by which DNA directs protein synthesis- Two stages of gene expression o Transcription - occurs inside the nucleus o Translation - occurs in the cytosol of the cellOne gene - one enzyme hypothesis:- A flaw with this hypothesis is that not all proteins are enzymes, so this lead the hypothesis of one gene-one enzyme to be inaccurate. One gene - one protein hypothesis:- A flaw with this hypothesis is that proteins are made up of more than one polypeptide, so specifying one gene to one protein is inaccurate. Proteins also comprise of beta and alpha structures that give it a dynamic function for genes to specify a single protein. One gene - one polypeptide hypothesis:- This is the best hypothesis, but still isn’t technically true, because it has been recently discoveredthat one gene doesn’t necessarily define one polypeptide, but also codes for certain RNA molecules involved in protein synthesis.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.Three differences between DNA and RNA:1. Double helix in DNA vs. Single stranded in RNA 2. Thymine is in DNA vs. Uracil takes the place of Thymine in RNA3. Deoxyribose structure lacks an oxygen vs. Ribose structure has oxygen Transcription in Prokaryotes 1. Initiation begins at the Promoter region 2. Elongation occurs with the help of RNA polymeraseRNA polymerase pries DNA strands apart and joins RNA nucleotidesRNA polymerase doesn’t need primerRNA polymerase processed in a 5’ to 3’ direction3. TerminationRNA polymerase falls off after reaching stop codon The mRNA is ready for use and will processed to translation without any modification to mRNA Transcription in Eukaryotes 1. InitiationPromoter starts initiation o Promoter binds after seeking the TATA box, which are repeating codes of TATATA that signal transcription factors to bind to the region to start initiation o Transcription errors lead to diseases.o Transcription factors make up a huge part of DNA (10%)o This region where initiation begins is called the Transcription Initiation Complex - - o Prokaryotes don’t have transcription factors 2. ElongationRNA polymerase copies 40 nucleotides/secSingle genes can be transcribed simultaneouslyRNA polymerase unwinds DNA and adds nucleotides to growing mRNA strand3. TerminationTerminator sequence tells the RNA polymerase to stopIn eukaryotes, the mRNA strand goes through modification before beginning translationo Polyadenylation signal sequenceRNA Splicing- Introns – non-coding regions- Exons – expressed regions (or regions that exit)- Splicesomes - protein complex made up of snRNAs (small nuclear RNA) that make up snRNPs (small nuclear RNA protein complex). Together they make the splicesome. Importance of Introns- Alternative RNA splicing- 1 gene can encode more than 1 polypeptide- The # genes ≠ # protein productsRNA Processing after Transcription - In eukaryotic cells there are enzymes that alter both ends of primary transcript mRNAo 5 prime cap is attached to mRNA o 3 prime poly A tail is attached to mRNA o Prokaryotes don’t have a nuclear membrane so their mRNA is ready for translation, unlike eukaryotes - Function of these modification in eukaryotes o Seem to facilitate exiting nucleus o Protect mRNA from hydrolytic enzymes o Ribosome attachment Why need an RNA intermediate?- Protects DNA blueprint - Allows copies of protein to be made simultaneously, this makes it more efficient - Many RNA transcripts can be made from one geneCodons- Codon are series of non-overlapping, three nucleotide ‘words’ that provide the genetic instructions for a polypeptide found in mRNAEvolution of the genetic code- It is nearly universalTranslation in Prokaryotes and Eukaryotes - mRNA is translated into protein - Interpreter is the tRNA - translational RNA - Site of translation is at the ribosomeTransfer RNA- Transcribed from DNATranslation1. InitiationmRNA binds to small subunit tRNA binds to mRNA start codon AUGLarge subunit then binds to the small subunit, finally making a ribosomal site for translation to occur 2. ElongationMoves from the Active site to Polypeptide site, where the chain of polypeptides are formed Then the empty tRNA, that has already translated its codons to a protein moves to the Exit site, where it leaves.3. TerminationStop codon is a release factor that adds water, this begins hydrolysis, which breaks the subunits apart. Post translation- Spontaneous folding (secondary and tertiary)- The polypeptide chain go into Chaperonin cells that protects the chain and folds the chain properly- During post translational modifications:o Sugars, phosphates, lipids, etc. can be added o Removes few Amino Acids from the N-terminuso Cleaving of the polypeptide chains can occur o The original chain may join with other polypeptide chains to make complex proteinsPolyribosomes - Are an array of ribosomes that consequently translate mRNA in a chain to make polypeptide chains fasterTypes of Point MutationsSubstitutions- Often have the least effect on an organism, leads to Missense or Nonsense mutations Insertions and Deletions- Almost always disastrous causes Frameshift mutationsPoint mutations- If occurs in germ cells, can cause hereditary disease- Change in a single nucleotide can lead to abnormal proteinsGeneral DNA and RNA Overview- Francis Crick named the dogma. DNA - RNA - Protein - DNA polymerase moves 5’ to 3’ direction - RNA polymerase moves 3’ to 5’ along template strand- DNA and RNA are polymers of nucleotides- Proteins are polymers of amino acids - Genes are hundreds to thousands of nucleotides long- DNA and RNA have two different chemical languages!- mRNA is complementary not identical to DNA template - Diseases are necessarily not in the genes but in the switches that regulate