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Chapter 12 Alterations of Chromosomes. You Must Know How alternation of chromosome number or structurally altered chromosomes (deletions, duplications,

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Presentation on theme: "Chapter 12 Alterations of Chromosomes. You Must Know How alternation of chromosome number or structurally altered chromosomes (deletions, duplications,"— Presentation transcript:

1 Chapter 12 Alterations of Chromosomes

2 You Must Know How alternation of chromosome number or structurally altered chromosomes (deletions, duplications, etc.) can cause genetic disorders. (This includes nondisjunction from chapter 11)

3 Female Butterfly: XY (This is normal) X(This is not lethal) Male Butterflies: XX (This is normal) XXX (This is not lethal) The 1 st division of the fertilized egg divides the embryo into the future right and left halves of the butterfly. Propose a hypothesis to explain how you could end up with a butterfly that is ½ male and ½ female. Female Male

4 mitosis

5 Polyploidy is a condition in which an organism has more than two complete sets of chromosomes – Triploidy (3n) is three sets of chromosomes – Tetraploidy (4n) is four sets of chromosomes Polyploidy is common in plants, but not animals Octiploid (8n)!

6 Alterations of chromosome structure Deletion Duplication Deletion Duplication Inversion Deletion Duplication Inversion Translocation

7 Disorders Caused by Structurally Altered Chromosomes The syndrome cri du chat (“cry of the cat”) results from a specific deletion in chromosome 5. A child born with this syndrome has severe cognitive difficulties and has a catlike cry; individuals usually die in infancy or early childhood.

8 Normal chromosome 9 Normal chromosome 22 Reciprocal translocation Translocated chromosome 9 Translocated chromosome 22 (Philadelphia chromosome) leukemia

9 Review Slide Meiosis I Nondisjunction Meiosis II Non- disjunction Gametes Number of chromosomes Nondisjunction of homo- logous chromosomes in meiosis I (a)(b) Nondisjunction of sister chromatids in meiosis II n  1 n − 1 nn


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