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Genetics & Inheritance Tuesday 10 /22/13

Genetics & Inheritance Tuesday 10 /22/13. B eyond Mendel Incomplete Dominance Co-Dominance / Multiple Alleles Environmental influence I nheritance patterns pedigree analysis autosomal vs. X-linked traits Chromosomal Basis of Inheritance gene linkage

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Genetics & Inheritance Tuesday 10 /22/13

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  1. Genetics & Inheritance Tuesday 10/22/13 • Beyond Mendel • Incomplete Dominance • Co-Dominance / Multiple Alleles • Environmental influence • Inheritance patterns • pedigree analysis • autosomal vs. X-linked traits • Chromosomal Basis of Inheritance • gene linkage • non-disjunction in meiosis last outline • Material in this outline is fair game for Exam two (a week from today) • Will start evolution on Thursday – will be on Exam three

  2. Inheritance of Traits: • characteristics are passed down across generations • genetic counseling looks at the • homozygous dominant and heterozygous individuals • heterozygous is • one tool is use of pedigree analysis to determine (or try to determine) the inheritance pattern of the disorder

  3. Pedigree Analysis: • Types of inheritance patterns: This chart shows an autosomal recessive pattern -

  4. Patterns of Inheritance: • autosomal dominant • autosomal recessive

  5. Patterns of Inheritance: • X-linked recessive • XAXA & XAXa • XAY - • XaXa • pattern of inheritance different for males & females • males • all sons • all affected daughters

  6. Gene Linkage: • crossing over during meiosis exchanges alleles • when genes are • if the genes are on the same chromosome fig 24.2 • the closer together two genes are the more likely they will not be separated during crossing-over

  7. Chromosomes not splitting during Meiosis: • Meiosis - process of making gametes • Errors in meiosis - - • nondisjunction -- • during Meiosis I - • during Meiosis II - • Note:

  8. fig 24.7 non-disjunction in Meiosis II non-disjunction in Meiosis I • Results: gamete with an extra OR missing chromosome • if occurs inmeiosis I - • if occurs in meiosis II

  9. Examples: • (1) Down’s Syndrome • trisomy 21 • 1 out of 700 children • syndrome - Most trisomies are NOT viable - exceptions are fig 24.8

  10. Nondisjunction in Sex Chromosomes: • (2) Klinefelter syndrome - • nondisjunction • phenotypic results:

  11. Nondisjunction in Sex Chromosomes: • (3) Turner’s syndrome - • nondisjunction in egg or sperm • 1 in 2500 female births • tend to be • treatment with

  12. Testing for Chromosomal Anomalies fig 24B, pg488 • Amniocentesis: • risk – increase in spontaneous miscarriage • Chorionic villus sample:

  13. fig 24.9 Chromosomal mutations: • typically a • lacks a • may vary William’s syndrome: deletion of part of ch. #7 poor academics & health issues, highly verbal/musical friendly fig 24.10 inv dup 15 syndrome: part of chromosome 15 duplicated and inverted poor muscle tone / autistic characteristics

  14. NON-Disjunction Exercise: Starting with the cell below, draw out meiosis showing non-disjunction occurring during meiosis I. Be sure to show the duplication of the chromosomes, label the homologous chromosomes and the sister chromatids. Label the non-disjunction, indicating what goes wrong. Note: this cell shows the sex chromosomes PRIOR to duplication! AT THE END of your meiosis drawing indicate with an arrow(s) the abnormal gametes. Y X

  15. In which type of nondisjuction (meiosis I or meiosis II) does a triplo-X (XXX) individual inherit two X chromosomes from her father?

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