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Gonosomal Inheritance: Heredity of Genes on Sex Chromosomes

This educational material provides an overview of gonosomal inheritance, focusing on the inheritance patterns of genes located on the sex chromosomes, X and Y. The material covers topics such as chromosome structure, gene transfer, and inheritance control by sex.

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Gonosomal Inheritance: Heredity of Genes on Sex Chromosomes

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  1. 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

  2. heredity of signs whose genes are placed on sex chromosomes (in the heterologous part of the chromosome) GONOSOMAL INHERITANCE

  3. www.uni-heidelberg.de/presse/news05/2501genetisch.html • chromosome X • chromosome Y SEXUAL CHROMOSOMES

  4. 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

  5. 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) > theyprovedirect inheritance • genes lying in heterologous section of chromosome X prove so called X - chromosomal inheritance SEXUAL CHROMOSOMES

  6. 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 SUMMARY

  7. 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 GENES FULLY CONNECTED WITH THE SEX

  8. 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

  9. 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 HEMOPHILIA

  10. 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 CROSS INHERITANCE

  11. by mammals usually small • few genes • key geneSRY • it influences: • production of male hormon • maturation of sperms • these geneshave direct inheritancefrom father to son = holandric inheritance CHROMOSOME Y

  12. 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 INHERITANCE CONTROLLED BY SEX

  13. 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

  14. EARLY HUMAN ACOMIA

  15. 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.

  16. 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

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