Lecture 7 Outline - In a pedigree, recessive X-linked...

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Bio 352 1 of 4 LECTURE 7 : Pedigree Analysis Today’s topics : 1. Autosomal recessive 2. Autosomal dominant 3. X-linked recessive 4. X-linked dominant 5. Y-linked Readings : Pierce, pgs. 134 - 142 Constraints on the study of human genetics Pedigree analysis Symbols used in pedigrees ( Fig. 6.2 ; last page of outline.) Things to look for in a pedigree: 1. Are approx. equal numbers of males and females affected? 2. How many affected parents does an affected child have? 3. Does the trait seem to "skip a generation"? 4. What is the approximate phenotypic ratio of families? Autosomal dominant trait Example : Waardenburg syndrome ( Fig. 6.3 )
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Bio 352 2 of 4 Autosomal recessive trait Example : albinism ( Fig. 6.4 ) Important Assumption : For individuals with a rare recessive trait, you will have to make some decisions about which grandparents are carriers. When the decision is unclear, assume that individuals with normal phenotypes from outside the pedigree are NOT heterozygous. X-linked recessive trait (Fig. 6.7)
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Unformatted text preview: In a pedigree, recessive X-linked inheritance can be identified by: Phenotype found only (or almost always) in males. Affected males have normal sons! Affected males usually have normal parents, but may have affected uncles, granduncles If a womans father was affected, but she is not, approximately 1/2 of her sons will be. (the trait skips a generation.) Example : hemophilia ( Fig. 6.8 ) Bio 352 3 of 4 X-linked dominant trait (Fig. 6.9) Dominant X-linked inheritance can be identified by: Both males and females affected. Trait does not skip generations. Affected males have normal sons, but all of their daughters are affected. Affected females pass the trait to half of their daughters and sons. Y-linked trait (Fig. 6.10) Only males affected. Trait always passed from father to son. Summary (see Table 6.1 ) Next Time : Linkage and Recombination I (Lecture 8) Bio 352 4 of 4 Readings : Pierce, pgs. 160 170; 173 - 175...
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This note was uploaded on 05/07/2011 for the course BIOLOGY 352 taught by Professor Townsend during the Spring '08 term at San Diego State.

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Lecture 7 Outline - In a pedigree, recessive X-linked...

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