2014

GONOSOMAL INHERITANCE

Výukový materiál GE 02 - 52

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

GONOSOMAL INHERITANCE

heredity of signs whose genes are placed on sex chromosomes

(in the heterologous part of the chromosome)

SEXUAL CHROMOSOMES

chromosome X chromosome Y

www.uni-heidelberg.de/presse/news05/2501genetisch.html

SEXUAL CHROMOSOMES

chromosome Y much smaller than X big heterologous part of chromosome X

forms a special binding group= inheritance fully connected with the sex

genes on a small homologous section of both chromosomes are subjects to synapsis

crossing over can proceed > inheritance like autosomal genes = inheritance not fully connected with the sex

SEXUAL CHROMOSOMES

genes lying in the heterologous section of chromosome Y determine holandric features, e.g. excessive hair of auricle

genes carried on chromosome Y are transferred only on males (heterogametic sex) > they prove direct inheritance

genes lying in heterologous section of chromosome X prove so called X - chromosomal inheritance

SUMMARY on gomosomes there can be distinguished between

heterologous and homologous sections. heterologous sections: they determine features completely connected with sex homologous sections: they determine features not completely connected with

sex, i.e. Mendel´s lawns in force features incompletely connected with sex are

determined by genes lying in homologous sections of chromosomes (e.g. daltonism, blindness)

for these genes are valuable the same rules as for autosomal genes

GENES FULLY CONNECTED WITH THE SEX

they lie on the heterologous part of the chromosome X

a big number of genes genes whose recessive alleles cause: hemophilia Daltonism (colorblindness) absence of sweat glands (anhydrotic

ectodermal dysplasia) muscle dystrophy

HEMOPHILIA

genotype of a healthy woman: XX >> both dominant alleles

genotype of a woman-vector: Xx >> she has a dominant allele on one chromosome and on the other one a recessive defect allele

>> otherwise, she is healthy but she can transfer a defect on the next generation on sons

genotype of an ill woman: xx >> on both X chromosomes defect alleles

HEMOPHILIA

in the genotype of a man there is only one X chromosome, the alleles located on it do not have any counterparts = hemizygotic organism

these alleles always become evident in the phenotype

genotype of a healthy man: XY genotype of an ill man : xY

CROSS INHERITANCE

daughters inherit defect from the disabled father mother vector tranfers the disease on her sons = cross inheritance typical for genes fully connected with sex noticeable difference in the frequency of illnesses

between the sex > much more common by the individuals of type XY than XX

genes localized on heterologous part of chromosomes Y do not have their pair allele in genotypes XY, the organism hemizygotic for them > they can become evident by the sex XY only

CHROMOSOME Y

by mammals usually small few genes key gene SRY it influences: production of male hormon maturation of sperms these genes have direct inheritance

from father to son = holandric inheritance

INHERITANCE CONTROLLED BY SEX features whose genes are located

on autosomes they become evident in dependence

on the presence of sexual chromosomes in phenotype by both the sexes differently

formation of the most secondary sexual features

early hairlessness

early acomia (hairlessness) allele P responsible for early acomia by men: it appears in homozygotic dominant and

heterozygotic constitution men PP and Pp are bald (hairless), pp are

not women: they have this cosmetic fault only by

genotype PP women pp and Pp have normal hair

INHERITANCE CONTROLLED BY SEX

EARLY HUMAN ACOMIA

WORKSHEET

EXAMPLE 1:Father and son are colour-blind, while the mother distinguishes colors normally. Is it right, when we say that son has inherited this hereditary defect of sight from his father? The recessive allele, conditioning daltonism, lies in the non-homologous segment of chromosome X.

EXAMPLE 2:A daughter of a colour-blind father has married a man whose father was also colour-blind. However, neither the woman nor the man suffer from daltonism. What will their children be like? The recessive allele, conditioning daltonism, lies in the non-homologous segment of chromosome X.

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

SOURCES