IHNERITANCE OF QUANTITATIVE FEATURES Výukový materiál GE 02 - 53 Tvůrce: Mgr. Šárka Vopěnková Tvůrce anglické verze: ThMgr. Ing. Jiří Foller Projekt: S anglickým jazykem do dalších předmětů Registrační číslo: CZ.1.07/1.1.36/03.0005 Tento projekt je spolufinancován ESF a SR ČR 2014

QUANTITATIVE FEATURES genotypically conditioned by a larger amount of genes with a small effect – polygenes, which influence each other with their effect and which form a polygenic system the most of multicellular organisms phenotypical evidence of particular alleles add to each other in polygenic additive system the effect of alleles multiplicate in polygenic multiplicative system

QUANTITATIVE FEATURES by a big amount of active genes is formed a big amount of quantitatively different genotypes by a monogenous feature are formed 3 genotypes (AA, Aa, aa) if each gene is represented by two alleles, by the number of genes k is the number of various genotypes given by expression 3k if a feature is influenced by three genes, 27 various genotypes are formed

QUANTITATIVE FEATURES by 5 participating genes 243 genotypes are formed so quantitative features show a continual variability – Gaussian curve because the effect of each polygene is very small, it is difficult to distinguish the influence of polygenes from the influence of external environment!!!

QUANTITATIVE FEATURES the share of external factors, non hereditary variability by the formation of phenotype of quantitative features can be figured out the mass of inheritance and non-hereditary variability = heritability is given by the relation between hereditary and total phenotypical part of the feature variability

QUANTITATIVE FEATURES the index of heritability is so called coefficient of inheritance = h2 h2 = Vg/Vp h2 is the quotient of genetically conditioned variability in total phenotypical variability of a particular feature

HERITABILITY values of coefficient of inheritance are from 0 (total variability of the feature is caused by factors of the environment) to 1 (total variability of the feature is caused by genetic factors) values of h2 lower than 0,2 are regarded as low heritability values 0,2 – 0,5 as medium heritability values over 0,5 as high heritability the higher heritability, the higher similarity between parents and the posterity is to be expected and on the contrary!!!!!!

QUANTITATIVE FEATURES they usually have low heredity marks of their genes are easily influenceable by factors of the environment some influences of the external environment strengthen the mark significantly, some of them inhibit it non hereditary variability, changing the phenotype of quantitative features, is called modification

QUANTITATIVE FEATURES Laplace-Gauss curve of normal values distribution of a quantitative feature in the population (the curve is bell-shaped) b) Variation curves of two features with various but in both cases normal distribution of the variation in the population

QUANTITATIVE FEATURES Model analysis of normal values distribution curve of a polygenic (quantitative) feature in the population (the empty circle marks a neutral allele – not influencing the height; each black circle marks a 1 cm taller stature

WORKSHEET In the second generation of the posterity after interbreed crossing hens of type Bantam and Plymouth following values were marked by a random sample of ten adults: 1030 g, 1210 g, 1560 g, 1390 g, 1160 g, 870 g, 910 g, 1220 g a 1410 g. What is average body weight, which can be theoretically expected in this collection of hybrids? What range of values of body weight of adult individuals may occur in this collection under specific conditions?

SOURCES CHALUPOVÁ-KARLOVSKÁ, Vlastimila. Obecná biologie: středoškolská učebnice : evoluce, biologie buňky, genetika : s 558 řešenými testovými otázkami. 2., opr. vyd. Olomouc: Nakladatelství Olomouc, 2010, 206 s. ISBN 978-80-7182-282-0