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Sex-Linked Inheritance

Sex-Linked Inheritance. Chapter 12.2. Sex-linked Inheritance. The 23 rd pair of chromosomes determines whether you are male or female, these are called sex chromosomes . The other 22 pairs of homologous chromosomes are called autosomes. Sex-linked Inheritance.

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Sex-Linked Inheritance

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  1. Sex-Linked Inheritance Chapter 12.2

  2. Sex-linked Inheritance • The 23rd pair of chromosomes determines whether you are male or female, these are called sex chromosomes. • The other 22 pairs of homologous chromosomes are called autosomes.

  3. Sex-linked Inheritance • Sex chromosomes are labeled with the letters X and Y. • They are named because of their shape. • Male genotype is XY • Female genotype is XX

  4. Sex-Linked Traits • Sex-linked traits are traits controlled by genes located on the sex chromosome. • Some examples of recessive sex linked traits are: - Colorblindness - Hemophilia

  5. Sex-Linked Traits • Alleles for sex linked traits are written as superscripts of the X or Y Example: Xb For Males: • Because X and Y are not homologous, the Y chromosome has no corresponding allele to the one on the X chromosome, no superscript. Example: XbY ( recessive trait is expressed)

  6. Sex-Linked Traits For Females: • A recessive trait on X chromosome follows the same rules as dominance. Example: XBXb = does not express trait XbXb = expresses trait

  7. Sex-Linked Traits • Carrier = is someone who carries the recessive trait, but does not express that trait • Example: XBXb = does not express recessive trait. Expresses dominant trait.

  8. PRACTICE • Cross a colorblind male with a normal female.

  9. PRACTICE • On your whiteboards • complete # 1 on worksheet “Sex-Linked Traits – Can you see what I see?” (p22 in packet)

  10. Ticket out the Door On a separate sheet of paper answer the following question. A woman heterozygous for normal vision has a baby girl that is colorblind. Two men claim to be the father of the child. One man is colorblind and the other is not. Which one is most likely the father? Create two punnet squares to prove your answer.

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