Genetic Vocabulary what is a Genome The total genetic endowment of a species what do we call the alleles YOU possess your individual genetic makeup genotype The alleles you posses define your genotype or hereditary makeup The way they are expressed physically is called what your phenotype the sum of observable traits You can t always tell a person s genotype from what you see on the outside from their phenotype Homozygous both alleles in the pair are the same Heterozygous two different alleles in a pair Remember one allele in the pair will come from your mother and one from your father The alleles you posses define your genotype or hereditary makeup The way they are expressed physically is your phenotype the sum of observable traits When you have heterozygous alleles Recessive the allele in the pair that is not expressed in your phenotype Dominant the allele in the pair that is the only one expressed in your phenotype Co dominant both alleles are partially expressed Any particular trait can be determined by any number of loci Single gene trait monogenic inheritance Polygenic inheritance two or more genes work together to affect some trait character Hemoglobin by 2 loci Skin color by many we don t know how many Monogenic trait Trait affected by change at only one locus Even though it is a change in only one locus it may have many phenotypic effects Example albinism Affects skin hair eyes On top of that environmental factors may play a role in producing many phenotypic traits cancer sunburn bad eyes Point mutation A mutation of single codon or sometimes of a single base in a codon Example Sickle cell anemia results in abnormal blood cells normal sickle Results from a mutation on chromosome 11 the amino acid valine is substituted for glutamic acid at position 6 kvhs nbed nb ca gallant biology point mutation html Macromutation a mutation with important or far reaching results Example change in the rate of development This is the kind of mutation hypothesized to have played a critical role in the development of bipedalism in humans Polygenic traits Traits affected by more than one gene Polygenic traits are least easy to figure out and are also affected by the environment Example stature In most cases we don t have a clear idea of the way polygenes combine to influence a trait Keep in mind that many of the traits we ll be examining in our study of human evolution are far from simple they often are polygenic traits The transmission of polygenic traits tends to produce intermediate phenotypes Sex linked genes Genes that occur only on the X or Y chromosome http openlearn open ac uk mod resource view php id 193030 Unlike other chromosomes which occur in homologous pairs there are two different types of sex chromosomes The X chromosome carries a lot of hereditary information but the Y seems to specify little apart from sex Sex linked genes are significant when they involve a harmful recessive gene The male will express that trait because there is no dominant allele to suppress it Example red green color blindness This trait is carried on the X chromosome A female may be a carrier but not express it She has a 50 50 chance of passing it on to her son Sex linked genes Another example hemophilia Normally fatal and would be lost But occurs as a mutation c every 50 000 parents Queen Victoria was a carrier 4 9 children 8 26 grandchildren 6 34 great grandchildren Quick Review of Basic Genetics for Understanding Evolution A mutation with far reaching effects one that could begin a new species is called a macromutation A trait affected by a single gene is called a monogenic trait Traits with intermediate types are often affected by one gene or by multiple genes They are often polygenic traits affected by more than one gene A gene that occurs only on the X chromosome is what kind of gene A sex linked gene If a harmful recessive gene occurs on the X chromosome of a male will it be evident from his phenotype Yes because there is no corresponding allele that could mask it A change in the allele frequency of a population over time is the definition of what word evolution What is the source of different alleles mutation What are the sources of individual variation from generation to generation due to sexual reproduction 1 Mutation 2 Segregation Independent assortment 3 Crossing over leading to recombination 4 Linked genes The total genes of a population is called Gene pool What is a population a group of individuals that interbreeds What is a species A population or group of populations that is capable of interbreeding and is reproductively isolated from other populations A group of organisms that can produce fertile offspring among themselves but not with other groups What does the Hardy Weinberg Equilibrium Principle state That evolution will NOT happen the allele frequency of a population will NOT change IF Four conditions are met What are the four conditions that if met would lead to no change in the gene pool of a population from one generation to another Mating is entirely random No geographic or social barriers The population is large enough No genetic drift skewing due to small population size No new variants are introduced into the gene pool No mutations no gene flow All individuals are equally successful at surviving and reproducing No natural selection forces What are the sources of change in a population over time what are the mechanisms of evolution 1 Mutation 2 Natural selection 3 Genetic drift 4 Gene flow What do we call the introduction of new genetic material into a population Gene flow What do we call the free or wide ranging exchange of genetic material within a population Gene flow TRUE FALSE Natural selection is constantly changing any one species making it evolve FALSE Only when the environment or selective forces change will natural selection work to advantage a different range of alleles Otherwise we may see Stabilizing selection Natural selection promotes stability because there is no environmental change Or Oscillating selection Adaptive variation around a norm in response to environmental variation What is the result when a group out of a population splits away taking their alleles out of the main gene pool Genetic drift What do we call a change in allele frequency of a population by random fluctuations Genetic drift When a group is small and begins a new population isolated from others what do we call that The founder effect because the population fissioned Will that small
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