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Segmental, Componential, & Contextual Changes

Segmental, Componential, & Contextual Changes. Dan Graur. Segmental = involving two or more adjacent nucleotides Componential = affecting gene content Contextual = affecting gene context. Point substitution. Reciprocal Recombination. Gene Conversion. Tandem duplication. Deletion.

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Segmental, Componential, & Contextual Changes

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  1. Segmental, Componential, & Contextual Changes Dan Graur

  2. Segmental = involving two or more adjacent nucleotides • Componential = affecting gene content • Contextual = affecting gene context

  3. Point substitution

  4. Reciprocal Recombination

  5. Gene Conversion

  6. Tandem duplication

  7. Deletion

  8. Conservative transposition

  9. Duplicative transposition

  10. Inversion

  11. Horizontal gene transfer

  12. DNA duplication (by size) 1. internal gene duplication 2. complete gene duplication 3. partial chromosomal duplication (partial polysomy) 4. complete chromosomal duplication (polysomy) 5. genome duplication (polyploidy)

  13. Extent of DNA Duplication Mutational Occurrence Possible Effects on Fitness partial gene very frequent Deleterious if it affects reading frame. whole gene frequent Deleterious if expression is determined by gene number. Almost invariably deleterious. partial polysomy rare polysomy common Almost invariably deleterious. polyploidy common Deleteriousness may be determined by the mode of reproduction and sex-determination.

  14. Polysomy: Complete chromosomal duplication  deleterious e.g., trisomy 13

  15. Partial Polysomy: Partial chromosomal duplication deleterious Partial Trisomy 16q+ A partial duplication of 16q from band q13 to q24

  16. DNA duplication 1. internal gene duplication 2. complete gene duplication 3. partial chromosomal duplication 4. complete chromosomal duplication 5. genome duplication

  17. Equal & Unequal Crossing Over The main mechanism responsible for gene duplication is unequal crossing-over.

  18. Variation begets Variation

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