2014

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

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

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

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

AUTOSOMAL INHERITANCE

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

III. Law about independent combinability of alleles by observation of 2 alleles simultaneously there happens the same

regular segregation2 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

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

AUTOSOMAL INHERITANCE

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

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

AA aa Aa

RECIPROCAL RELATION BETWEEN ALLELES

  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?

WORKSHEET

Example 2 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 red-

fruit 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?

• 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.

SOURCES