Transcript autosomal inheritance

AUTOSOMAL INHERITANCE
Výukový materiál GE 02 - 51
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
AUTOSOMAL INHERITANCE
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homozygotic genotype - homozygote:
individual, that inherited from both the parents the
same allele of the same gene (AA, aa, BB, bb)
heterozygotic genotype - heterozygote
Individual with two different alleles of the same
gene ( Aa, Bb)
Parental generation => P
Direct descendants => first filial generation F1
next generation => second filial generation F2,F3,..
AUTOSOMAL INHERITANCE
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hereditary features contained in autosomes
without reference to gene binding
by every diploid descendant allele pair consists of:
1) one father´s allele
2) one mother´s allele
transfer of alleles on descendants is subject to basic
rules of combinatorics
the first solving this matter - Mendel
=> combinational (Mendelian) squares
3 Mendel´s laws
AUTOSOMAL INHERITANCE
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I. law about uniformity
F1 (1st filial = first
generation of
descendants)
by reciprocal crossing of 2
homozygotes originate
descendants genotypically
and phenotypical uniform
If there are 2 different
homozygotes
descendants are always
heterozygotic hybrids
AUTOSOMAL INHERITANCE
II. Law about coincidential gene
segregation into gametes
 by the crossing of 2 heterozygotes can
each of two alleles (dominant and i
recessive) be given to the descendant
with the same probability
 so it comes to genotypic and also
phenotypic splitting = segregation
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AUTOSOMAL INHERITANCE
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Probability for the descendant is :
25% (homozygotic dominant individual) : 50%
(heterozygote) : 25% (homozygotic recessive
individual)
genotype splitting relation 1:2:1.
phenotype splitting relation 3:1
If there is a codominance relation between alleles,
phenotypic splitting relation corresponds with genotypic
splitting relation (1:2:1).
AUTOSOMAL INHERITANCE
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III. Law about independent combinability of alleles
by observation of 2 alleles simultaneously there happens the same
regular segregation
2 dihybrids AaBb can each of them form 4 different gametes (AB,
Ab, aB, ab)
by the reciprocal crossing of these 2 gametes are formed 16
various zygotic combinations
9 various genotypes (relation 1:2:1:2:4:2:1:2:1)
phenotype splitting relation je 9:3:3:1.
the law is in force if :
observed genes occur on different chromosomes
gene binding is so weak that it cannot prevent their free
combinability
AUTOSOMAL INHERITANCE
AUTOSOMAL INHERITANCE
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Complete dominance and recessivity
 in heterozygotic genotype occurs only a
dominant allele
 Recessive does not occur
 allele A determines red colour of the flower
 allele a determines white colour
 individual with genotype Aa will be red
AA
aa
Aa
RECIPROCAL RELATION BETWEEN ALLELES
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incomplete dominance and recessivity
both alleles take part in the formation of a feature,
usually in unequal degree
 individual with heterozygotic genotype differs
from both homozygotes
 A special case– intermediarity (both proves in the
same degree)
 allele A determinates red colour of the flower,
allele a white, individual with genotype Aa will be
pink
AA
aa
Aa
RECIPROCAL RELATION BETWEEN ALLELES
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codominance
in heterozygotic genotype occur both alleles
next to each other
 they do not suppress each other
e.g. blood groups of the system AB0
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AA
aa
Aa
WORKSHEET
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Example 1.
The gene for the formation of black colour in cattle
is dominant over the gene for red color (they are
two different alleles of the same gene).
What posterity (F 1) will be obtained after crossing
purebred, i.e. homozygous black bull with red cow?
What will be the composition of the posterity of
hybrids obtained by crossing each other (in F 2)?
And what calves will be obtained by crossing with
red bull F1 hybrid cows from?
Example 2
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For tomatoes, the gene responsible for the red colour
of the fruit is dominant over the gene for yellow colour
(they are two different alleles of the same gene).
What colour will the fruits of plants obtain by crossing
homozygous red-fruit with homozygous yellow-fruit
plants?
What plants will bear fruit in the F 2?
Specify the posterity obtained by crossing plants of redfruit plants of F 2 with a hybrid plant of F1? Will be
composition of posterity of such crosses always equal,
or will it be different by some red-fruit plants of F2?
What colour will have plants in the posterity of the
reciprocal crossing of yellow-fruit plants between each
other?
Example 3
A blue-eyed man, whose parents both have
brown eyes, married a girl who has brown
eyes and whose father was blue-eyed, while
his mother was brown-eyed.
 Their only child so far has brown eyes.
 What are the genotypes of the child, the
parents and all the grandparents, if you know
that brown eye colour is dominant over blue?
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SOURCES
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KUBIŠTA, Václav. Obecná biologie: úvodní učební text biologie pro 1. ročník
gymnázií. 3. upr. vyd. Praha: Fortuna, c2000, 103 s. ISBN 80-716-8714-6.