Fundamentals of Life Science I BIOL 2150 002 Dr Brenda Leady 8 25 14 Exam 1 Review Chemical Cellular and Evolutionary Foundations The Scientific Method Observation Discovery science Hypothesis Educated guess based on observation Predictions What you believe will happen when you perform experiments on your hypothesis Experiments or new observations Actions performed to try to validate your hypothesis THEORY o Predictions must be testable Hypothesis are only supported or not supported not true or false What is life Living things and nonliving share the same chemical basis and follow the same physical laws 1 st Law of Thermodynamics o Energy can neither be created nor destroyed o Energy can only be transformed 2 nd Law of Thermodynamics o The degree of disorder in the universe tends to increase over time o Entropy is a measure of disorder of a system the simplest self replicating entity that can exist as an independent unit of life ALL living organisms use DNA to store and transmit information Cell Nucleic acids DNA RNA Protein Viruses are NOT alive Variation can be environmental or genetic Four Classes of Molecules o Nucleic acids o Proteins o Lipids o Carbohydrates Genes are DNA sequences that encode information to make a specific RNA or protein Gene product How do genes encode information o Order of nucleotides in a gene is specific to a product o Nucleotides ATGC in DNA Single Units The DNA sequence is transcribed into a RNA copy of the DNA sequence The RNA sequence is decoded by the ribosome to produce the appropriate protein Mutations change the DNA sequence of a gene forming new alleles o Mutations can be good bad or nothing at all Alternative form of a gene Allele Note A mutation or allele can be lost if the individual does not reproduce Different alleles can result in the production of variant forms of the encoded protein Anything that alters structure alters function in Biology Genotype and Phenotype The particular alleles within particular individuals define that individual s genotypes Phenotype is determined by genotype The detectable structure and function of an individual is the phenotype of that individual HBa HBa Normal HBs HBs Sickle cell disease HBa HBs Malaria resistant Genotype determines how well adapted an individual is to their environment How well adapted an individual is to its environment depends on its phenotype Malaria resistant Will live longer be healthier and have more children in areas Phenotype directly interacts with the environment Alleles that provide an advantage in a particular environment will become more infested with the malaria parasite common in that environment The HbS allele is much more common in humans who live in areas with high malaria infection rates Diploid organisms have 2 copies of each gene One allele of each gene is inherited from the mother and the other from the father A diploid organism or cell is also sometimes designated as 2n Homozygous The two alleles are the same Heterozygous The two alleles are different For each gene a diploid organism can be either homozygous or heterozygous Meiosis Sexual reproduction results in variation Fertilization results in the new diploid organism in diploid organisms results in the production of haploid gametes Meiosis Diploid germ cells two alleles of each gene Haploid sperm one allele of each gene Haploid egg one allele of each gene A haploid organism or cell is also sometimes designated as 1n New combinations of alleles in every offspring Natural selection is the process of competition and unequal reproduction of offspring Variation is phenotype Environmental or genetic Ultimate source of genetic variation is mutation Evolution Change over time Increase in variation Mutation Favors reproductive success of better adapted variants Selection Evolution Even though Adeline penguins are uniforms in appearance they are actually 2 3 times more genetically variable than humans Species Group of individuals that can exchange genetic material through interbreeding or share alleles through reproduction Gene pool All the alleles present in all individuals in a species Populations Interbreeding group of organisms of the same species living in the same geographical area What can cause genetic variation Mutation Somatic Germ Line Deleterious Neutral Advantageous Recombination o Adaptions Changes that make the individual better able to survive Allele frequency of copies of an allele total of alleles in population Peas have yellow and green alleles for seed color If all peas in a population are green aa then a is 100 and A is 0 This population is fixed for that allele Observable Traits Fails to consider Traits that are encoded by more than one gene The effects of the environment in which the population is found Gel Electrophoresis Charged molecules separate by charge and size All negatively charged molecules attracted to positive charge DNA or protein Problem Mutation had to cause difference in migration Smaller molecules travel faster DNA Sequencing Gold standard every difference detectable Evolution A change in allele or genotype frequency in a population over time Hardy Weinberg Equilibrium Certain conditions result in no change No change from generation to generation When we find changes evolutionary forces are at work There can be no differences in the survival and reproductive success of individuals no selection Populations must not be added to or subtracted from by migration There can be no mutation The population must be sufficiently large to prevent sampling errors genetic drift Individuals must mate at random Natural Selection Charles Darwin Alfred Russel Wallace NS Change in allele s frequency over time based on that particular allele s impact on survival and reproduction Individual that is best adapted to survive due to advantageous alleles leaves more offspring and as a result the next generation is enriched with the same advantageous alleles Modern Synthesis Ronald Fisher suggested that there could be several genes that contribute to a trait like human height Discrete vs continuous variation Synthesis between Darwin s theory of natural selection and Mendelian genetics Types of Selection Positive Increase frequency Negative Decrease frequency Balancing No strong positive or negative effect Heterozygote advantage AS resistant to malaria Sexual Selection Natural selection was acting to reduce the size and showiness of the nail Sexual selection was acting in the opposite direction Tail is a
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