Genetics 330 week 2
Genetics 330 week 2 Bio 330, Genetics
U of L
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This 6 page Class Notes was uploaded by Catherine Montz on Monday February 29, 2016. The Class Notes belongs to Bio 330, Genetics at University of Louisville taught by Dr. Perlin in Spring 2016. Since its upload, it has received 50 views. For similar materials see Genetics and Molecular Biology in Biology at University of Louisville.
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Date Created: 02/29/16
Genetics and Molecular Biology 330 Professor Perlin Exam 2 Weekly notes 2/23/16 Todays class began with a focus on promoters and enhancers. We will mainly be focusing on Eukaryotes. Promoters (piece of DNA) 1. Bound by transcription factors 2. Located close to T1 (transcription start site) 3. Conserved consensus sequences 4. Only used for 1 gene 5. Located upstream (before) the gene: has defined distance 6. Has some level of basal expression Enhancers (piece of DNA) 1. Bound by regulatory proteins (or regulatory TF’s) 2. Distance doesn’t need to be close to T1, there is no defined distance 3. No conserved consensus sequences 4. There is more than 1 gene affected 5. Can be upstream, downstream, or within the gene 6. Used for regulation of transcription Know that regulatory proteins and transcription factors need to bind to the DNA For enhancers we have a few exceptions we need to note for the “no conserved consensus sequences” There is a specific sequence that enhancers will use known as UAS. Upstream, Activation, Sequence. UAS = ATGCAAA DNA Binding Domains Let’s be familiar with some domains here First we have the helix - turn - helix As you can see, there is a turn that is in the middle of the helix. This structure will form within a protein. It is found within many of the proteins that are important in gene expression and it is a structural motif capable of binding DNA. Next we have the leucine zipper. It is a dimer formation. It is simply the pairing of leucines. Know that regulatory proteins are involved in transcriptional activation along with 30-100 amino acids. Sacchromyces corevisiae (yeast) - Follows galactose metabolism pathway Here is a breakdown of the galactose pathway: You have Gal4, which increases expression in Gal7, Gal10, Gal1. However; if Gal80 interacts with Gal4, then expression decreases in 7 and 10 and 1. Essentially transcription is prevented because galactose is not present. Now say we introduce galactose, have Gal2 serve as a channel for galactose, the inducer. The inducer will bind to Gal3 and interact with Gal80. Gal3 keeps 80 from binding to 4 in the presence of galactose so transcription can occur. Hormones Hormones are chemical signals Break down: A steroid hormone binds to steroid hormone receptor which binds to DNA. This changes transcription levels. Steroid hormone - inducer Steroid hormone receptor - regulatory proteins Steroid hormone receptor domains DNA binding domain Steroid binding Nucleus entry Transcription activation DNA RNA Protein Phenotype DNA RNA 1. Needs regulatory proteins 2. DNA methylation occurs to block transcription a. Fetal to adult; some fetal genes are turned off by methylation b. cell differentiation occurs through methylation c. x chromosome inactivation can occur Here are some examples: me - cytosine = methylation can occur naturally 5 - aza - cytosine = methylation cannot occur (this is not naturally occurring) 3. DNA amplification (selective/reversible) Example: xenaphus frog - they make lots and lots of ribosomes, so they have to have lots and lots of rRNA. During development there are many copies of this gene that codes for rRNA 2/25/16 Regulation of expression from RNA Protein Splicing removes introns from RNA to mRNA, which becomes composed of a shorter strand of exons Mouse amylase - protein different to function/ location 1. Salivary liver - alternate splicing can create different forms of the same protein depending on the way one RNA is spliced 2. Anti-sense RNA control Complimentary RNA can base pair and inhibit transcription/translation They target for destruction 3. Phage R17 There is a coat protein gene that makes a coat protein right before replicase. Replicase makes copies of ssRNA. Each phage R17 needs 1 molecule coat protein and 1 molecule of ssRNA (1 molecule of replicase makes 100 molecules of ssRNA) More coat protein is necessary than replicase S.D, recognition site for ribosome-binding of replicase gene is then shadowed once there is a certain concentration of coat protein which will prevent translation (this is how it is regulated) Regulation of expression from Protein Phenotype 1. Phosphorylation - activates on inactive particle proteins 2. End - product inhibition (feedback inhibition) Compound A E1 Compound B E2Compound C E3 Compound D E4 Comound E E5 Compound F Compound D interacts with E2 to inhibit production of C from B *Must cut off production at last possible compound in order to not end production of other compounds Mutation - change in the sequence of the primary genetic material (DNA for cells; DNA/RNA for viruses) Mutant - product(s) of mutation; organism; protein, RNA, phenotype UV light Thymine-thymine dimers form due to DNA damage from UV lighting. They are produced when adjacent thymine residues are covalently linked by exposure to UV radiation. Damage-Repair Enzymes Error-prone, may fix dimer but when filling the empty space they make many mistakes, or mutations Over time, such mutations effect function of the cell cancer Spontaneous loss of purines (depurination) 4 10 /cell/day Makes DNA susceptible to a break, causes weakened stability Promotes damage-repair, can create mutations They are hotspots for mutations but considered random - - Lac and Trp are placed into an agar medium. Secreting Lac -: glucose (trp can’t make trp so without trp, it can’t grow) Secreting Trp : cannot break don lactose
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