Week 6 Gene Expression In the embryo all genes are turned on o totipotent all powerful o stem cells o Differentiation Protein Synthesis DNA RNA Proteins The Central Dogma o Transcription DNA RNA o Translation RNA Proteins As we develop on 10 of our genes are expressed in our cells Differences in DNA and RNA DNA 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 ACGU Types 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 Mutations can affect the structure of the protein the gene is folding for which can then render the protein dysfunctional illness 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 mutation creates a new gene in a population very biologically important Review of Terms Eukaryotic cells Chromosomes A gene is a portion of DNA that codes for a protein Each gene can have several alleles or alternative forms have a nucleus are long strands of DNA and associated proteins Prevailing Viewpoints 1600s a premade human was in every sperm cell Laws of Inheritance created by Mendel he used pea plants to study inheritance easy to grow quick thought that offspring traits were a blend from each parent 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 alleles o 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 TT o Homozygous recessive tt o 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 generation o 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 7 Incomplete 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 environment the earth was young 6 000 years and species didn t change Prevailing Viewpoints before Darwin 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 change Evolution 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 He studied similarities and differences that influence survival and reproduction in Artificial Selection human directed dog and plant breeding lead to Darwin s idea of Species traits 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 and local 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 to whether it is a dry or wet season which effects the hardness of seeds 3 Modes of Natural Selection Stabilizing Selection Selection Directional Selection Disruptive 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 Drift change in allele frequency due to chance If a individuals form a new isolated population their traits will dominate the new population founder s effect o Bottleneck effect if a population is hit by a catastrophic event then the dominant traits will be of the survivors Week