Chapter 1 Notes
Chapter 1 Notes Bio 230
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This 5 page Class Notes was uploaded by Elizabeth Notetaker on Tuesday January 19, 2016. The Class Notes belongs to Bio 230 at West Chester University of Pennsylvania taught by Dr. Donze- Reiner in Spring 2016. Since its upload, it has received 37 views. For similar materials see Genetics in Biology at West Chester University of Pennsylvania.
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Date Created: 01/19/16
Introduction 3 fields of genetics: 1. transmission genetics 2. molecular- developmental genetics 3. population-evolutionary genetics Section 1.1: Birth of Genetics "like begets like" has long been understood, but mechanism behind this was unknown o God- some thought that a higher power gave you what you desired o blending theory- like blending paint (white + red = pink) problems: exceptions, traits haven't averaged out (only pink) Gregor Mendel o pea plant experiment pure white + pure purple = all purple offspring + offspring = 3:1 ratio of purple: white o traits act like particles(genes), not fluids (they don't mix) o somatic cell= body cell o gametes= sex cell o allele= variants in genes, either dominant or recessive Mendel's experiment went relatively undiscovered for many years. Baetson took Mendel's paper and travelled with it to show the world. Baetson came up with the term genetics- the study of inheritance. Over the next few years, many questions were answered in response to Mendel's work: where in the cell are genes? 1910- Thoman H. Morgan came up with chromosome theory. Two other scientists, Sutton and Boveri, also came up with similar theories around the same time. Morgan came up with the proof needed to prove this theory. can this explain human height and other continuously variable genes? Fisher (a statistician) realized that continuously variable genes can be controlled by multiple Medelian genes because they follow a bell-curve distribution. (more on this in ch. 19) how do genes work in a cell to control traits? 1941- Edward Tatum+ George Beadle: one-gene-one-enzyme hypothesis one gene directly encodes for one enzyme. Example ~ purple color gene codes for an enzyme that creates purple pigment what are genes made of? 1944- Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that genes are made of deoxyribonucleic acid (DNA) how does DNA store information? 1953 Watson+ Crick found double helix made of 4 bases (adenine, thymine, guanine, and cytosine) which form a code a+t is held by double hydrogen bond g+c is held by triple hydrogen bond they bond because of the complementary shapes and charges of the bases how are genes regulated? 1961- Jacob + Monod discovered: regulatory elements- (parts of DNA where an activator/repressor protein binds) which regulate... gene expression-whether a gene is "on" or "off" how is information in DNA used to makeproteins? Scientists from around the world "cracked the code" andfigured out how 4 bases can code for 20 amino acids. Also, ribonucleic acid (RNA) was discovered to be a messenger molecule of DNA's information through the cytoplasm where the proteins are synthesized. this basic "flowchart" of DNA to protein is known as the central dogma. central dogma: DNA replication- process of copying DNA in cell division transcription- DNA to mRNA (m=messenger) mRNA is the template for protein synthesis translation- mRNA to protein mRNA has 3-letter "words" called codons made from nucleotides (A,T,C,G) which correspond with a specific amino acid. All of these amino acids connect to make a protein. Section 1.2 After Cracking the Code model organism- a species used in experiments assuming that what is learned from the analysis of that species will hold true for other species, especially closely related species. Model organisms are from many different branches of life (bacteria, plants, or animals) examples~ fruit flies, Arabidopsis thaliana, Caenorhabditis elegans. Features of a model organisms: 1. small & inexpensive 2. short generation time a. experiment goes quicker 3. small genome a. easier to find genes 4. large # of offspring produced & easy to mate Variety in organisms is necessary for being a good model organisms. If there is no variety, there is nothing to change/ manipulate/ test. tools for genetic analysis 1. using cells own machinery for DNA manipulation: copying, pasting, cutting, transcribing a. DNA polymerases make copies of DNA by matching nucleotides b. nucleases cut out parts of DNA c. ligases join DNA end to end d. fluorescent or radioactive tags are used to track DNA 2. cloning DNA a. using DNA polymerase to make many copies of a small portion of DNA and inserting it into a host organism 3. transformation: inserting foreign DNA a. recipient of foreign DNA becomes a genetically modified organism (GMO) 4. hybridizing DNA molecules a. heating (denaturing) DNA molecules and tagging them so that when they cool and reattach scientists can see where on the chromosome the genes are 5. DNA sequencing a. figuring out the exact A, T, C, G order 6. genomics- study of entire genomes a. more math/ statistics oriented b. categorizing genes, mutations 1.3 Genetics Today a lot about genetics is still unknown: aging, looks ACDC- arterial calcification due to deficiency of CD73, caused by inheriting 2 copies of recessive gene this is a recently discovered genetic disorder caused by relatedness of parents single nucleotide polymorphisms (SNPs)- differences in DNA segments in 1 base pair: cause mutations of proteins (different shapes, shorter or longer) 2 observations were made: older parents tend to have a higher rate of birth defects, and fathers are more likely to contribute new mutations to their children than mothers. These were hard to test until we have genomic technology. 2012- 219 individuals from families of 3 had their genomes sequenced. Scientists looked for point mutations- a change in one nucleotide (common). They can track which parent this mutation arose from. Scientists found that there were thousands of mutations but only a few posed health risks. This study confirmed that older age(of fathers) increases likelihood of mutations and that fathers pass mutations more often than mothers. why does father's age matter and not mother's age? A woman's eggs are made entirely before she is born, while a man's sperm is made throughout his lifetime. More cell replications(age)= more possibility for mutations quantitative trait locus (QLT)- a trait that is controlled by more than 1 gene & normally acts as a spectrum (lights to dark purple) example~ rice's tolerance to deep flood waters is because of a gene locus called SUB1 SUB1 is an ethylene response factors (ERFs) which codes for regulatory proteins (regulate gene expression) and affects how the rice reacts to high water levels o plants with this quality react differently to high water levels by entering a hibernation like state rather than trying to grow out of the water & using up all of its energy because scientists knew where the gene was located, they could transfer it to other kinds of rice precisely, producing the best kind of rice possible without transferring undesired traits Recent Evolution in Humans why do genes change over time? in humans, three main factors are (1) pathogens, (2) temp, altitude, radiation, (3) diet high altitude adaptations: chronic mountain sickness (CMS) affects ability to reproduce UNLESS you've developed adaptations One variant of a gene (EPAS1) occurs much more in high land people than low land. This gene regulates red blood cell count and makes more RBCs when the body is in a low oxygen state. Increased level of RBCs would cause blood clots and hypertension, but the variant form of this gene seems to have found a loophole to this for high elevation dwelling people. lactose tolerance the gene for lactase is normally shut off in late childhood. However, adults who could digest lactose survived better in the event of scarce food. Now, many people can digest lactose through adulthood this is an example of natural selection
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