Week 4 - How Genes Work (Ch. 16), Evolution (Ch. 25)

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Biological Sciences
BIOSC 0150
Laurel Roberts

Week 4 Monday, September 16, 2013 6:00 PM Concepts Covered This Week: How Genes Work (Chapter 16) Evolution (Chapter 25) How Genes Work You should be able to… • Explain the relationship between gene, RNA and polypeptide (the Central Dogma) • Show how to test an enzymatic pathway for mutations • Use the genetic code to translate nucleic acid sequences into polypeptide chains • Explain the significance of the different mutations discussed in class The Central Dogma = Gene Expression = Protein Synthesis • DNA (information storage) ○ Transcription • mRNA ○ Translations • Proteins • Metabolic Pathwaysand the "1-Gene, 1-Enzyme"Hypothesis Ex: Changes in genotype cause changes in phenotype… The Genetic Code • Codon is comprised of three nucleotides ○ 64 different combinationspossible Genetic Code: mRNA → amino acid • Three different stop codons ○ May be because random mutation is more likely to stop production than to start it • Start codon is always AUG (b) TAC GAC CTC CCC CAA TCT GTA AUG CUG GAG GGG GUU AGA CAU AUG CUG GAG GGG GUU AGA CAU Met Leu Glu Gly Val Arg His Mutations affect phenotypes. How? Point Mutations • Silent Mutation: Changes the nucleotide sequence, but in a way that does not change the amino acid produced • Missense Mutation: Changes the nucleotide sequence, which changes the amino acid produced by that codon codon • Nonsense Mutation: Changes the nucleotide sequence, producing a stop codon early • Frameshift Mutation: Addition or deletion of a nucleotide, which changes the reading frame of the codons. This causes every amino acid after this mutation to possibly change the amino acid produced ○ Frameshift mutation at the beginning will have a greater impact than a frameshift mutation near the end Sickle Cell Anemia • Missense Mutation (chromosome11) • AutosomalRecessive disorder • Glutamine has a charge (O )- • Valine is nonpolar ○ Causes the clumped hemoglobin • Sickled red blood cells get stuck in the capillaries ○ Often in the joints ○ Causes extremepain Ryan Clark suffered a Sickle-Cell crisis while in Denver for a Steelers-Broncosgame. Hospitalized, surgery, etc Ryan Clark does NOT have SCA…. What DOES he have? • Sickle Cell Trait Condition where an individual has only one allele coding for abnormal hemoglobin protein ○ Condition where an individual has only one allele coding for abnormal hemoglobin protein A S A A S S  Hb Hb as opposed to Hb Hb (normal)or Hb Hb (SCA) • Symptoms ○ Most are asymptomatic ○ Problemsduring exercise/overexertion/anaerobicconditions NCAA Policy: The "Ryan Clark Rule" • Those who test positive can still participate in athletics ○ Cost: $5-10,paid for by University ○ Conformationtest ($35) is performed ○ 2nd positive test → education on ways to avoid complications • Results of tests will be kept confidential to all ○ Exception:Those involved in providing athlete with care during competition,practice and conditioning  Ex: Team doctors, athletic trainer, etc. ○ Area of possible concern? • NFL performstheir own test for sickle cell trait during NFL Combine ○ GINA (Genetic Information Non DiscriminationAct) Understanding Evolution You should be able to… • Explain the basic concepts of Darwinian Evolution ○ Descent with modification ○ Natural selection • Use the examples discussed in class to explain: ○ How speciation is occurring in real time ○ Why populations may currently exhibit low allele diversity
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