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Inheritance of Sex and Sex-Linked or Influenced Traits

Inheritance of Sex and Sex-Linked or Influenced Traits. Sex Determination. Sex chromosomes determined at fertilization _____ = female _____= male Sperm determines sex Females only make ___ eggs Males make ________ sperm. Can We Influence the Sex?. Historical Views

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Inheritance of Sex and Sex-Linked or Influenced Traits

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  1. Inheritance of Sex and Sex-Linked or Influenced Traits

  2. Sex Determination • Sex chromosomes determined at fertilization • _____ = female • _____= male • Sperm determines sex • Females only make ___ eggs • Males make ________ sperm

  3. Can We Influence the Sex? • Historical Views • Thought __________ determined the sex • Thought the __________________ determined the sex • Some Current Theories • Chemical environment of female reproductive tract • Timing of sex around _______________

  4. Comparing the Chromosomes • X chromosome • ____________ genes • Y chromosome • ___________ genes • Sex-determining region of the Y (_______ gene)- gene that codes for maleness

  5. Looking Closer at the Y • Very small • Tips are called pseudoautosomal regions • Genes similar to genes on X • Can recombine with X • Middle section called male-specific region (MSY) • Genes essential to fertility including SRY • Genes nearly identical to X • Amplicons- regions of palindromes

  6. Sex Development • During fifth week of development • Unspecified gonads form • Two duct systems form • Mullerian ducts- will develop into ________ structures • Wolffian ducts- will develop into ________ structures • During sixth week • In males- SRY gene is activated • In females- no SRY gene, other genes control development

  7. What does SRY do? • Codes for a __________________that activates other genes controlling male development • Indifferent gonads develop into testes • Secrete anti-Mullerian hormones which causes these ducts to degenerate • Secrete testosterone to stimulate some internal male structures to develop • Some testosterone is converted to dihydrotestosterone (DHT) which cause external and some internal male structures to develop

  8. When Things Go Wrong • Androgen insensitivity • XY chromosomes • Testosterone is produced but receptors are absent or faulty • Phenotypic, but infertile, she • Male pseudohermaphroditism • XY chromosome • Block in testosterone production • Phenotypic she at birth • At puberty, other sources of testosterone are produced and male characteristics start to develop

  9. Severe Combined Immune Deficiency Syndrome

  10. Sex-Linked Traits • Y-linked Traits • Rare because so few genes • None currently well understood besides infertility • Trait would be passed from ______________ • X-linked Traits • Can be recessive or dominant

  11. Recessive X-Linked Traits • Expression • Females- ______________________ • Males- only need one copy (_____________) • Inheritance • Fathers pass mutated allele to all ___________ • Mothers pass mutated allele to _______________

  12. Dominant X-Linked Trait • Both females and males only need one copy • Females are usually less severely affected because one X is still ok • Some disorders are _________ in males

  13. Sex-Linked Punnett Squares • Same as other Punnett squares • Mom on one side, Dad on other • Need to write it like this: ___________ • Y does not have a letter

  14. Calico Cats

  15. X Inactivation • Occurs during early embryonic development • Each cell inactivated about ______ of one of the X chromosomes • Which X is chosen at random • All cells in that lineage will have the same inactivation

  16. Barr Bodies • X chromosome is inactivated by attaching __________(epigenetics) • Inactive X chromosomes absorb more stain creating a Barr body in the cell • Males do not have a Barr body

  17. Consequences of Inactivation • In _____________ disorders • Females can have patches of tissue that express mutant allele • Most of the time enough parts are normal to not have the effects of the disorder • Manifesting heterozygote- female who expresses mild form of disorder because of inactivation • In _____________ disorders • Females have normal and abnormal tissues throughout body

  18. Sex-Limited Traits • Traits can be inherited on autosomal or sex chromosome • Trait only affects __________________ • For example • Beard growth • Pregnancy- Preeclampsia • Milk production

  19. Sex-Influenced Trait • May be inherited on autosomal or sex chromosome • Sex of individual __________________ • May be dominant in one and recessive in the other

  20. Genomic Imprinting • Another form of epigenetics • Gene from specific parent is silenced in each generation using attached methyl groups • Methyl group are removed during meiosis and replaced once new embryo forms • Most seem to control early embryonic development

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