Genetics: Quantitative Inheritance PDF January 16, 2025

GENETICS A.F. Salvador | January 16, 2025 naturally fall into a small number of discrete QUANTITATIVE INHERITANCE categories Normal Distribution- a distribut...

GENETICS A.F. Salvador | January 16, 2025 naturally fall into a small number of discrete QUANTITATIVE INHERITANCE categories Normal Distribution- a distribution for a large I. Quantitative Traits sample in which the trait of interest varies in a II. Polygenic Inheritance symmetrical way around an average value III. Heritability Statistical Methods are used to evaluate a frequency distribution quantitatively I. Quantitative Traits predict how much the dependent variable Calculating the Mean changes in response to the independent variable. Complex traits- characteristics that are T determined by several genes and are significantly influenced by environmental factors Quantitative Traits- a measurable phenotype emerging from genetic and environmental Variance- a measure of the variation around the factors that is distributed in magnitude in a mean population rather than all or none. Covariance- describes the relationship between two variables within a group Regression Analysis- predict how much the dependent variable changes in response to the independent variable. History 1900s- Francis Galton & Karl Pearson - showed that many traits in humans and Biometric Field- involved the statistical study of domesticated animals are quantitative in biological traits nature Discontinuous traits- Often controlled by a - developed various statistical tools for single gene or a small number of genes. studying the variation of quantitative traits - Environmental factors may have less within groups of individuals influence on their expression compared to continuous traits. - Mendelian inheritance patterns (like dominant and recessive inheritance) are often observed in these traits. Frequency Distribution- alternative way in describing quantitative traits that do not Page 1 of 5 GENETICS 3RD YEAR, 1ST SEM III. Heritability II. Polygenic Inheritance Heritability- amount of phenotypic variation within History a group if individuals that is due to genetic variation. William Bateson & William Castle Geneticists partition quantitative trait variation into - traits are governed by genes, which are components that are attributable to the following inherited as discrete units different causes: - quantitative traits is difficult because these - Genetic variation (VG) traits are controlled by multiple genes and - Environmental variation (VE) substantially influenced by environmental - Variation due to interactions between factors genetic and 1909- Herman Nilsson-Ehle - environmental factors (VG×E) - experiment with wheat hull color - Variation due to associations between demonstrated how multiple genes can genetic and interact to produce a range of phenotypes - environmental factors (VG←→E) Genotype-environment Interaction - when two NOTE: different genotypes respond to environmental variation in different ways In polygenic traits, the effects of Genotype-environment association- use statistical multiple genes can be additive, meaning associations between allele frequency and that each gene contributes a small, environment of origin to test the hypothesis that incremental effect to the overall allelic variation at a given gene is adapted to local phenotype. environments. Polygenic inheritance, combined with - very common in the study of human environmental factors, plays a crucial genetics, in which large families tend to role in shaping the continuous variation have more similar environments than the observed in many traits within a population as a whole. population. Broad-sense heritability- all genetic factors Polygenic Inheritance- transmission of a trait affecting heritability, which includes the additive governed by two or more different gene effects of alleles, effects due to dominant/recessive Quantitative Trait Locus- location on a relationships, and effects due to epistatic chromosome that harbors one or more genes that interactions. affect the outcome of a quantitative trait Narrow-sense heritability- due to the additive Quantitative Trait Locus Mapping- involves the effects of alleles. analysis of a large number of markers and offspring Inbreeding- the mating of individuals or organisms - allow researchers to analyze the DNA that are closely related through common ancestry sequence in that region and to the identify Inbreeding Depression—the reduced survival and one or more genes that influence the trait of fertility of offspring of related individuals showing interest that variation for heritable fitness traits occurs within populations. Page 2 of 5 GENETICS 3RD YEAR, 1ST SEM Selective breeding- programs and procedures - It often involves the exchange of genetic designed to modify phenotypes in commercially material between different species. important plants and animals. Biological Species Concept- Ernst Mayr - a species is a group of individuals whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring but cannot successfully interbreed with members of other species. Evolutionary lineage Concept- George Gaylord Simpson - a species should be defined based on the Monomorphic- all the members of a population are separate evolution of lineages homozygous for the same allele of a given gene. General Lineage Concept- Kevin de Queiroz Hybrid Vigor or Heterosis- first introduced by - Each species has evolved from a specific George Shull series of ancestors and, as a consequence, - a phenomenon in which a hybrid progeny or forms a group of organisms with a particular F1 phenotype is superior when compared to set of characteristics any of its parental inbred lines. Anagenesis- Gradual evolutionary change within a single lineage, leading to the transformation of one Evolution species into another. Cladogenesis- The splitting of a single lineage into - heritable change in one or more characteristics of two or more distinct lineages, leading to the a population or species from one generation to the formation of new species. next. - may occur via allopatric, parapatric, or sympatric speciation Microevolution- Small-scale changes in allele frequencies within a population over time (example: The increase in antibiotic resistance in bacteria.) Macroevolution- Large-scale evolutionary changes that occur above the species level, such as the origin of new species and the diversification of life. (example: The evolution of mammals from a common ancestor.) Molecular evolution- patterns and processes associated with evolutionary change at the molecular level. Such changes may be phenotypically neutral or they may underlie the Phylogenetic Tree- a graphical representation of the phenotypic changes associated with evolution evolutionary relationships between biological Horizontal Gene Transfer- organism incorporates entities, usually sequences or species genetic material from another organism without Maximum likelihood and Bayesian methods - used being the offspring of that organism. to discriminate among possible phylogenetic trees. Page 3 of 5 GENETICS 3RD YEAR, 1ST SEM POPULATION GENETICS Population- group of individuals of the same species that occupy the same region and can interbreed with one another - may change its size, geographic location, and genetic composition. GENETIC DRIFT: Founder Effect Vs. Bottleneck Effect Local Populations or Demes- a sub-population (a smaller group within the population) that can freely interbreed. Polyorphism- many forms Monomorphic- a population where only one form or phenotype of a particular trait exists Single Nucleotide polymorphism- a genomic variant at a single base position in the DNA. Used to study how a genome influence health, disease, drug response and other traits. Allele Frequency- calculated as the number of times an allele appears within sampled homozygous and heterozygous individuals divided by twice the number of individuals sampled Genotype Frequency- calculated as the number of individuals with a particular genotype divided by the number of individuals sampled Founder Effect- reduction in genomic variability that occurs when a small group of individuals becomes separated from a larger population. The resulting new subpopulation will have genotypes and physical traits resembling the initial small, separated group, and these may be very different from the original larger population. Hardy-Weinberg equilibrium- genetic variation in a Bottleneck Effect- events that limit genetic variation population will remain constant from one in a population and result in founding populations generation to the next in the absence of disturbing that can lead to genetic drift. factors - occur frequently during the natural life cycles of RNA viruses. Page 4 of 5 GENETICS 3RD YEAR, 1ST SEM LAST TOPIC: REVIEW YOUR CASE STUDIES AND THE BASIC PRINCIPLES OF CYTOGENETICS There are no computations 2 5 items- M CQ 3 5 items- id en tificatio n 2 0 items- en u meratio n an d Illu stratio n Read all th e P resen tatio n s o f all g ro u p s fro m b o th sets Reference: BROOKER, R. J. (2023). Genetics: Analysis and principles. MCGRAW-HILL EDUCATION. Page 5 of 5