Lecture 4 - Lecture 4 Sex linked single gene inheritance...

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Lecture 4 Sex linked single gene inheritance Introduction to pedigrees Mendel’s Second Law
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Many plants and animals exhibit sexual dimorphism. Individuals are either male or female as a result of inheriting either an X or Y chromosome paternally. X and Y chromosomes are termed sex chromosomes, as opposed to autosomes (all other chromosomes). At meiosis in females the one copy of the X chromosome is distributed into each gamete. In males the X and Y are distributed so that there are two types of gametes; two carry the X and two carry the Y. This equal distribution accounts Diploid number (46) Females: 44 autosomes + X X Males: 44 autosomes + X Y Very little in the differential  region is related to sex  determination/function.
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Sex-Linked Single Gene Inheritance Patterns Eye color in fruitfly…Note that eye color is unrelated to sex determination, the gene that specifies this characteristic is situated in the differential region of the X chromosome. Remember male and female have X…only male has Y. Therefore this gene is hemizygous. Hemizygous:  a gene present only in one copy in a diploid organism – for example an X-linked gene in a male mammal (or arthropod in this case!)
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Reciprocal cross: a pair of crosses where genotype A (female) X genotype B (male) and B (female) X (A male)
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Figure 2-27 part 2 Sex linked inheritance will show different  phenotypic ratios the two sexes of progeny and in 
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Human pedigrees: predicting outcomes of matings when progeny are few. • Newly detected (usually deleterious) phenotype is traced back
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This note was uploaded on 12/17/2009 for the course BIO Genetics taught by Professor Saxena during the Spring '08 term at University of Texas at Austin.

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Lecture 4 - Lecture 4 Sex linked single gene inheritance...

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