Transcript quantitative features

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
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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
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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!!!
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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 nonhereditary variability = heritability
 is given by the relation between
hereditary and total phenotypical part of
the feature variability
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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
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HERITABILITY
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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
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QUANTITATIVE FEATURES
a) 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
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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
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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