ch 28 complex and quantitative traits Flashcards
complex traits
characteristics that are determined by several gene are significantly influenced by environmental factors
quantitative traits
traits, usually polygenic in nature, that can be described using numbers
quantitative genetics
the field of genetics that studies complex and quantitative traits
continuous traits
quantitative traits that fall along a continuum rather than occurring in discrete categories
meristic traits
traits that can be counted and expressed in whole numbers
threshold traits
traits that are inherited through the contribution of many genes
frequency distribution
a graph that displays the numbers of individuals that are found in each of several phenotypic categories
normal distribution
a distribution for a large sample in which the trait of interest varies in a symmetrical way around an average value
biometric field
a field of genetics that involves the statistical study of biological traits
mean
the sum of all the values in a group divided by the number of individuals in the group
variance
a measure of the variation around the mean within a population
standard deviation (SD)
a statistic that is computed by taking the square root of the variance
covariance
a statistic that describes the degree of variation between two variables within a group of individuals
correlation coefficient (r)
a statistic with a value that ranges between -1 and +1; it indicates how two factors vary in relation to each other
polygenic
refers to a trait that is controlled by multiple genes
polygenic inheritance
the transmission of any trait that is governed by two or more different genes
quantitative trait locus (QTL)
the location on a chromosome of one or more genes that affect the outcome of a quantitative trait
QTL mapping
the determination of the locations of qtls using mapping methods, such as genetic crosses coupled with analysis of molecular markers
inbreeding
sexual reproduction between two genetically related individuals
monomorphic
a term used to describe a trait that is found in only one form in a population or a gene that is found as only one allele in a population
genotype-environment interaction
the phenomenon that occurs when the environment effects on phenotype differ according to genotype
genotype-environment association
the phenomenon that occurs when certain phenotypes are preferentially found in particular environments
heritability
the amount of phenotypic variation due to genetic variance within a specific group of individuals raised in a particular environment
broad-sense heritability
heritability that takes into account different types of genetic variation that may affect phenotype
narrow-sense heritability
heritability that takes into account only the additive effects of alleles
selective breeding
(also called artificial selection) programs and procedures designed to modify phenotypes in economically important species of plants and animals
selection limit
the phenomenon in which several generations of artificial selection results in a plateau where artificial selection is no longer effective
realized heritability
a form of narrow-sense heritability that is observed when selective breeding is practiced
inbreeding depression
the phenomeon in which inbreeding produces homozygotes that are less fit, thereby decreasing the reproductive success of a population
heterosis
(also called hybrid vigor) the phenomenon in which hybrids display traits superior to those of either parental strain; usually different from overdominance because the hybrid may be heterozygous for many genes, not just a single gene, and because the superior phenotype may be due to the masking of deleterious recessive alleles
