Genetics380_2009_Lecture9_24

Genetics380_2009_Lecture9_24 - Sept 24, 2009 Today:...

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Sept 24, 2009 • Today: Modifications and Extensions of Mendel’s Basic Principles (to be continued in Sept 29 lecture) • Quiz 1 next week: 15 minutes in recitation • Exam 1 in two weeks (Oct 8 th ): multiple choice; short answer/problem • Check Sakai Resources for last year’s exams and quizzes • Section 7 recitation will now meet in ARC 204. TA Larry Kramer. • Mid-course online evaluations: anonymous
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Sex-linked characteristics • X-linked inheritance • Y-linked • Disorders
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Morgan’s observation Pure breeding Red eye female White eye male PO F1 All red eye progeny (except 3 white-eyed males among 1237 progeny) F2 All red eye female 1/2 red eye male 1/2 white eye male Not expected result for a simple recessive trait, which should appear in what fraction?? of both male and female F2 offspring.
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Equalizes the amount of protein produced by X-linked genes in the two sexes. In male flies, doubled X activity. In C. elegans worms, X activity is halved on both Xs. In placental mammals, one X is inactivated in females. A Barr body is an inactivated X chromosome . Dosage compensation XX cell XY cell
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X-linked recessive: Color Blindness X-linked dominant: uncommon hypophosphatemia: vitamin D rickets hypertrichosis: excess body and facial hair Y-linked SRY and maleness No convincing cases of nonsexual phenotypic variants associated with Y. Hairy ear rims possible, but disputed.
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Tangent: Autosomal aneuploids Trisomy 21: Down syndrome Chromosome 21 has fewer genes than on any autosome, with only about 230 genes of a total of 20,000 to 25,000 for the entire human genome 1 in 700, incidence increases with maternal age Primary Down syndrome (92%): three full copies of chromosome 21. – Usually arises from nondisjunction in egg formation (meiosis I)
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This note was uploaded on 10/03/2010 for the course RUT 146:356 taught by Professor Gol during the Spring '10 term at Rutgers.

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Genetics380_2009_Lecture9_24 - Sept 24, 2009 Today:...

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