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Daily Objective

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  • Students will participate in class discussions on sex-linked traits in order to complete the “Sex-Linked Traits” worksheet.

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Notes

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  • Set up your notes for “Sex-Linked Traits”

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  • Corresponds with pg. 350-351

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Sex-Linked Traits

  • Sex-linked genes are the genes located on the x chromosome.

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  • They code for sex-linked traits.

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  • Sex-linked traits have a unique pattern of inheritance.

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Sex-Linked Traits

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  • Sex-Linked traits are more often expressed in males.

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  • WHY?

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Sex-Linked Traits

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  • Males are more likely to express recessive traits because they only get one copy of the x chromosome→one copy of the gene.

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Examples

  • Hemophilia- a blood disorder that causes the blood to take too long to clot.

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  • Children with the disease get small cuts and scrapes and can not stop the bleeding.

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  • This is sometimes fatal.

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Examples

  • Color Blindness: a disorder that causes people to be unable to distinguish between certain colors.

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Examples

  • Baldness

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Case Study

  • Ms. Moore’s grandfather was color blind. Her grandmother has normal sight and had no history of color-blindness in her family.

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  • Create a Punnett Square to show the possible genotypes and phenotypes for Ms. Moore’s mother.

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Case Study

  • Ms. Moore’s mother is a CARRIER for color blindness. This means that she has one recessive allele, but does not show the trait since she also has one normal allele.

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  • She can however, pass it on to her offspring…

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Case Study

  • Ms. Moore’s mother is a carrier for color blindness. Her father is normal.

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  • What is the probability that Ms. Moore is color blind? The probability that she is a carrier?

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Case Study

  • Assuming that Ms. Moore is a carrier for the color blindness gene and that her partner has normal vision, what is the probability that a daughter she has will be colorblind? A son?

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Case Study

Ms. Moore has a perfect little boy.

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If the probability of Ms. Moore being a carrier is 50% and the probability of her son being color blind if she is is 50%, what is the probability that her son is colorblind?