Lecture 4 - Lecture 4 Sex linked single gene inheritance Introduction to pedigrees Mendel’s Second Law Many plants and animals exhibit sexual

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Unformatted text preview: Lecture 4 Sex linked single gene inheritance Introduction to pedigrees Mendel’s Second Law Many plants and animals exhibit sexual dimor phism. 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 Ver y little in the differ ential r egion is r elated to sex deter mination/function. 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. H emizygous: 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!) Reciprocal cross: a pair of crosses where genotype A (female) X genotype B (male) and B (female) X (A male) Figure 2-27 part 2 Sex linked inher itance will show differ ent phenotypic r atios the two sexes of pr ogeny and Human pedigrees: predicting outcomes of matings when progeny are few....
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This note was uploaded on 01/08/2010 for the course BIO 51405 taught by Professor Ruhlman during the Fall '09 term at University of Texas at Austin.

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Lecture 4 - Lecture 4 Sex linked single gene inheritance Introduction to pedigrees Mendel’s Second Law Many plants and animals exhibit sexual

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