Download chromosome Y

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
2014
GONOSOMAL INHERITANCE
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heredity of signs whose genes are placed on sex
chromosomes
(in the heterologous part of the chromosome)
SEXUAL CHROMOSOMES
chromosome X
 chromosome Y
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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
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SEXUAL CHROMOSOMES
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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
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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
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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
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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
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CROSS INHERITANCE
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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
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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
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INHERITANCE CONTROLLED BY SEX
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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
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.
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