BIO 151 1st Edition Lecture 15 Outline of Last Lecture 1. Prokaryotic gene expression - mostly transcriptional, make RNA or not?2. Eukaryotic gene expression has many steps to control3. Specific transcription factors4. Transcription of Trp operon5. Regulation of eukaryotic transcription is often more complex6. Eukaryotic gene expression - many steps to controlOutline of Current Lecture 1. Mutations2. Nonsense mutations create new stop codons in DNA template for mRNA, make abnormally short proteins3. DNA nucleotide sequence contains information for...4. Mutations can remove or create new splice sites in DNA template for mRNA5. DNA arrangements can change gene expression6. Simplifying part of the central dogma - DNA replication via polymerase chain reaction (PCR)7. PCR geometrically amplifies DNA between the 2 primers, but need both DNA and a protein (DNA polymerase)8. RNA World Hypothesis9. Self-Replicating DNACurrent Lecture - Mutations:- defects in DNA sequence that change gene function- example: change in coding region for protein- silent mutations don't change amino acids- others might change amino acids (missense mutations), but these amino acids may or may not be critical to the protein- nonsense - change puts in a stop codon, ribosome will read it and release factor will bind - short, one amino acid protein- may or may not still functionNonsense mutations create new stop codons in DNA template for mRNA, make abnormally short proteins:- high % of human genetic diseases- some forms of --cystic fibrosis (ion channel in lung cells)-Duchenne muscular dystropy (scaffolding/cytoskeleton protein)- experiment treatment: drugs that cause ribosome to read through (skip) stop codons- change coding- Frameshift mutations - deletion or insertion of anything other than 3n nucleotides in coding region - causes extensive missense (1 base pair deletion)DNA nucleotide sequence contains information for:- where to bind RNA polymerase- where to bind transcription factors, alter transcription and histones- where to methylate DNA- where to 5' cap and polyadenylate eukaryotic primary RNA signal (bind enzymes to each)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.- where to splice eukaryotic primary RNA, intron-exon splice sites (bind snRNA of spliceosomes)- where to bind miRNAs- where to start and stop translation of mRNA (start and stop codons, bind initiator tRNA and release factor protein, respectively)- what amino acids to put in protein (codons bind tRNAs)Mutations can remove or create new splice sites in DNA template for mRNA:- example: one form of Progeria (premature aging)- single base substitution makes a new splice site in pre-RNA for Lamin A- mutations can change recognition sites for transcription factor binding- ex. DNA change in operator DNA might block binding of transcription factorDNA arrangements can change gene expression:- The central dogma (DNA to RNA to protein) and chemical evolution - biogenesisSimplifying part of the central dogma - DNA replication via polymerase chain reaction (PCR):- what, at a minimum, do you need to replicate DNA?- uses heat instead of helicase, topoisomerase, to separate DNA strands- use short DNA primers to start amplification in DNA - no primase!- uses DNA polymerase from heat-resistance bacteria, does not denature at high temps.PCR geometrically amplifies DNA between the 2 primers, but need both DNA and a protein (DNA polymerase):- self-replicating molecules- natural selection would operate on self-replicating molecules- system must contain enzymes that can generate many identical enzymes- What would they be?- self-replicating molecules could possibly be RNA - RNA? --can be a template-can be an enzyme - RNA enzyme = ribozyme- "RNA World" HypothesisRNA World Hypothesis:- RNA systems that self-replicate in 2 steps- ribozymes can spontaneously cause nucleotides to link together - act as RNA polymerasesSelf-Replicating RNA:- still lots of problems (efficiency of ribozyme, clutter with other molecules, etc.) some think there must have been something before RNA- getting beyond RNA - hypothesis1) Self-replicating RNA2) RNA acted as template for forming 3) Proteins then aid in replication of RNA4) Make DNA from RNA for storage of info.- Assume early cell has membrane DNA to RNA to protein = something like modern
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