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Week 6Gene Expression- In the embryo, all genes are turned ono totipotent- all powerfulo stem cells- As we develop on 10% of our genes are expressed in our cellso DifferentiationProtein Synthesis- DNARNAProteins - “The Central Dogma” o Transcription: DNARNAo Translation: RNAProteinsDifferences in DNA and RNADNA: stores RNA/protein coding information and transfers info to daughter cells, double stranded, deoxyribose sugar, nucleotide bases are ACGT RNA: helps make proteins and catalyzes reactions, single stranded, ribose sugar, nucleotide bases are ACGUTypes of RNA- Messenger RNA: (mRNA) carries info to a specific protein, 3 RNA bases form a “codon”, is a part of transcription - Transfer RNA: (tRNA) carries specific amino acid to ribosome, is a part of translation Transcription- Prokaryotes: ribosomes translate mRNA as soon as transcription is complete - Eukaryotes: mRNA is usually altered Transcription to Translation- “The Genetic Code” links RNA to proteins o mRNA codons specify 20 amino acids o also start and stop codons o highly conserved among specifies Translation- Protein folding: must achieve final functioning folding, errors in folding can lead to illness - Mutations: can affect the structure of the protein the gene is folding for, which can thenrender the protein dysfunctional Mutations- can be good, bad, or silent. Can cause disease - Types of mutations are: substitution, insertion (reading frame is shifted), and deletion - Insertions and deletions are more harmful that substitutions because they can alter the whole reading frame for the gene - Single gene disorders: one single gene is mutated, so the protein product can be changed or missed completely o Cystic Fibrosis: mutation that affects the transport of salt across a membrane so mucus builds up, lung cells are most impacted - Germline Mutations: mutations that can be passed to the next generation, the mutationcreates a new gene in a population (very biologically important)Review of Terms- Eukaryotic cells have a nucleus - Chromosomes are long strands of DNA and associated proteins - A gene is a portion of DNA that codes for a protein - Each gene can have several alleles or alternative forms Prevailing Viewpoints - 1600s: a premade human was in every sperm cell - thought that offspring traits were a blend from each parent Laws of Inheritance- created by Mendel, he used pea plants to study inheritance (easy to grow, quick reproduction, can be cross pollinated by hand, easily observable traits)- he found that tall plants were dominant, and short plants were recessive Laws of Segregation - during meiosis only one copy of each gene is placed in each gamete -- a diploid cell can only have two alleleso homozygous means the 2 alleles are the same (TT, tt)o heterozygous means the 2 alleles are different (Tt)- Genotypes express the genetic make up of an individual o Homozygous dominant: TTo Homozygous recessive: tto Heterozygous: Tt- Phenotypes are the description of the individual o Tall versus short, fat versus skinny - Mendel created a system to keep track of the cross matings o Parental generation: P generationo P’s offspring: F1 generation o F1’s offspring: F2 generation, etc…o Punnett squares uses genotypes to predict the offspring’s traits o Monohybrid cross: mating between two heterozygous individuals o In a monohybrid cross the genotypic ratio is [1 TT: 2Tt: 1tt]Week 7Incomplete Dominance: one allele for a specific trait is not complexly dominant over the other allele. Occurs when a heterozygote has an intermediate phenotype between 2 homozygotes Polygenic Traits: depends on more than one gene, which is reflected in the phenotype. Most inherited traits are polygenic (eye color) Sex-Linked Traits: sex linked traits are carried in the X chromosome. Patterns of inheritance differ from men and women- Males are XY. Females are XX To be color blind To have normal vision Environmental Effects - skin color is a polygenic trait that’s influence by the environmentPrevailing Viewpoints: before Darwin - the earth was young (6,000 years), and species didn’t change - advances in science lead to awareness in changes in the lines of descent - 18th-19th century naturalists tried to reconcile traditional beliefs with evidence of changeEvolution: genetic change in a population over time, and it’s not a theory centered on the origin of life, but instead how species change over time - Darwin’s HMS Beagle lead to new ideas about species, he published the Origin of Species- He studied similarities and differences (that influence survival and reproduction) in traits - Artificial Selection: human directed dog and plant breeding lead to Darwin’s idea of natural selection Natural Selection: differential survival and reproduction among individuals of a population whose traits vary, it is a mechanism of evolution - 3 conditions for natural selection o variation for a trait (running speed in rabbits vary each individual)o heritability (trait of running speed is passed from parent to offspring)o differential reproductive success (slower rabbits are eaten by foxes, so slow traits are not passed down to the next generation) more offspring are produced than can survive  must be a competition for resources the better competitors survive and reproduce - fitness: a measure of relative reproductive success - the result of natural selection is that a population will be well-adapted to its current andlocal environment (a fox will have white fur in the arctic, and brown fur in the desert)- natural selection doesn’t make a perfect organism, simply traits with better fitness are “good enough” for the organism to survive - traits can fluctuate regularly based on the environment (beaks of finches change due towhether it is a dry or wet season, which effects the hardness of seeds) 3 Modes of Natural Selection Stabilizing Selection Directional Selection Disruptive Selection Mechanisms of Evolution - Natural-Sexual Selection: some traits have greater fitness because they are attractive to mates (peacock feathers) - Mutation: can create a new allele in an individual, which creates a change in allele frequency in the population. It’s the ultimate source of genetic variation in a population- Migration: after a group of individuals migrate to a new population, both groups will experience changes in allele frequency-therefore experiencing evolution - Genetic


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OSU BIOLOGY 1101 - Gene Expression

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