week 1 genetics
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This 5 page Class Notes was uploaded by MelLem on Sunday October 2, 2016. The Class Notes belongs to BIOL 336 at Simmons College taught by Dr. Lopilato in Summer 2016. Since its upload, it has received 4 views.
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Date Created: 10/02/16
Genetics Biology 336 – Fall 2016 Lecture 1: Thursday 9-8-16 Human Genome Project, HGP – Write o “project would create genomes, plan follows closed controversial meeting” o project not yet approved by the NIH o possibility to replace CRISPR-Cas for gene editing? o Genome – the complete DNA sequence of an organism. What is CRISPR-Cas o Co-disovered by Dr. Jennifer Doudna, and Dr. Emmanuelle Charpentier. o Known as the gene editing tool o Fix mutations in cells – gene editing. o CRISPR-Cas – a tool for gene editing, RNA based. Allows you ro make single nucleotide changes in the genome. Allows you to replace defected genes, however the drawback is that there is off target mutations associated with it. What does our genome look like? o HGP – 99.9% same DNA sequence in everyone, only 4% encodes protein o exons- encode proteins Non-LTR retrotransposons Non-LTR retrotransposons ENCODE and modENCODE projects o Encyclopedia of DNA Elements – ENCODE Model organisms ENCODE – modENCODE o The aim – describe all functional elements in the human genome and in model organisms. o First released in 2012, second in 2014. Started in 2003 following the completion of the HGP in 2001. o 2012 claim : 80% of human genome has been assigned at least on biochemical function. o Function elements – sites on the DNA where the proteins bind. Model Organisms o Six model organisms are typically used to help further develop an understanding of cellular biology, genetics, and many more topics in biology. o Model organisms are organisms with similar genome size and number or genes. What does Genetics do? o Genotype phenotype Genotype – genetic composition, the DNA sequence Phenotype- appearance of an organism due to its genotype. o Cloning organisms o Cloning genes o Altering genes, silencing genes, activating genes o Editing genes – CRISPR-Cas o Silenecing whole chromosomes – done at UMass Worcester Medical school july 17 , 2013. DNA is the genetic material o Classical experiments Griffith’s experiment Avery, MacLeod, and McCarty o DNA is inherited – Hershey Chase experiment. o Structure of DNA was determined to be a double helix consisting of nucleotide sequences. AT GC o Griffith’s experiment: Transformation – when living bacteria take up DNA from the environment and have a different phenotype. In the experiment you’re going from non- pathogenic to a pathogenic. He injected living S cells into mice, and also living R cells, the S cells killed the mice, but a combination of the two killed the mouse that had originally only received the R cells and had survived. Genes Proteins o Inborn errors of metabolism can cause hereditary diseases o Proteins are encoded by genes o Defective proteins encode by mutant genes Genes and Environment o Pleiotropy – one gene can affect more than one trait o Any trait can be affected by more than one gene – polygenic trait o Most traits are affected by environmental factors as well as by genes. Chromosomal basis of inheritance o Mitosis o Meiosis o Chromosomes are duplicated in S phase before mitosis and meiosis. Mitosis o Chromososmes are duplicated in S phase before mitosis o Each duplicated chromosome has 2 sister chromatids o Chromosomes line up on the metaphase plate during metaphase. o Sister chromatids pull apart during anaphase of mitosis. o End result is 2 diploid daughter cells which occurs following cytokinesis which is the separation of the cell into new cells. o Goal is to create genetically identical cells – ie. Skin cells Meiosis o Occurs in the ovaries and testes to produce eggs and sperm. o Reduces the number of chromosomes bu half 2N N o Produces haploid gametes that differ genetically. o Goal is to create genetic variation among different organisms. Lecture 2: Tuesday 9-13-16 DNA is the genetic material o Classical experiments Griffith’s experiment Avery, MacLeod, and McCarty DNA is inherited – Hershey chase experiment o Structure of DNA was deduced Mendel o Had modern view of genetics 1) genes are discrete particles 2) Genes are inherited 3) Genes are responsible for traits o Genotype- genetic endowment – DNA – the sequence of genes o Phenotype – appearance of an organism due to its genotypic ratio. Mendel’s Monohybrid results o Deduced that a 3:1 Ratio results in the F2 generation o Statistical test – Chi Squared analysis gives the probability that the variation was due to chance. P > 5% means variation was due to chance and the deviation is NOT significant. Therefore the data supports a 3:1 ratio (hypothesis) P < 5% means that the variation was not due to chance and the deviation IS significant. Therefore the data does not support a 3:1 ratio (hypothesis) Mendel’s postulates o Genes are particles that come in pairs o Alleles are alternative forms of genes o Alleles segregate in the formation of gametes during meiosis o Genes move independently of each other o Gametes unite in random fertilization during meiosis Explanation of Mendel’s postulates o An allele is an alternative form of the gene Same allele WW or ww = homozygous Difference alleles Ww = heterozygous o Intact alleles transmitted from generation to generation via gametes Gametes = egg and sperm cells Gamete carries just ONE allele on each gene W or w Results of a monohybrid cross o F1 progeny all show dominant phenotype o See recessive phenotype in F2 progeny o 3 dominant : 1 recessive phenotypes seen in F2 progeny. o 1 WW : 2Ww : 1ww genotype ration in F2, which can be seen by examining the DNA of the SBEI gene.
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