1. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Structural Abnormalities Deletions Translocations Inversions Duplications

2. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

3. Deletions Small or large Mutation in one or many genes Homozygosity or heterozygosity for each Consequences for gene function

4. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Deletions Loss of chromosomal material Large-scale deletions are lethal Example: Cri du chat –Deletion of short arm of chromosome 5 –Affects motor and mental function –Infant cry resembles a meowing cat –Specific chromosomal break points are associated with specific phenotypic changes

5. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Cri du chat Syndrome Fig. 6.26 Variation in phenotype associated with region deleted has been observed Researchers have identified regions with genes involved in larynx and nervous system development

6. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Cri-du chat syndrome Deletion in Chrom. 5 Prader-Willi Syndrome Angelman Syndrome Deletions in Chromosome 15

7. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Structural Abnormalities Deletions Translocations Inversions Duplications

8. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Translocations Exchange of chromosomal segments between nonhomologous chromosomes Two major types –Reciprocal translocation –Non-reciprocal translocation

9. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Types of Translocations

10. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Burkitt’s lymphoma Ig- myc

11. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Reciprocal Translocation: yields normal and defective gamets  ABCDE  KLMN  ABMN  KLCDE Parent Has complete information  ABCDE  ABMN  KLMN Deletion and Duplication gametes  ABCDE  KLMN  ABMN  KLCDE Normal gametes

12. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Types of Translocations –Robertsonian Translocation Centromeres from two nonhomologous chromosomes fuse and chromosomal material from the short arms is lost 5% of Down syndrome cases involve a Robertsonian translocation between chromosomes 21 and 14

13. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Robertsonian Translocation A translocation between chromosome 14 and 21 may produce Translocation carrier Normal phenotype Translocation Down syndrome Lethal monosomy 21 Lethal trisomy 14 Lethal monosomy 14 Fig. 6.27

14. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Structural Abnormalities Deletions Translocations Inversions Duplications

15. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

16. New context Antennapedia Antp protein is made in antennal primordial cells, where the WT Antp does not express Legs grow out in Antp mutant in place of antenna Inversions reorganize DNA sequences

17. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Wild-type head Antp required for identity of T2 (Wings and legs) Expression of Antp in head results in legs forming in place of antennae Antp expressed in head

18. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Structural Abnormalities Deletions Translocations Inversions Duplications

19. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

21. Evolution of genes/gene families myoglobin  family ß family Hemoglobin family gene duplication divergence gene duplication divergence (~ 700 million years ago) (~ 450 million years ago) Primordial gene Encodes O 2 carrier protein

22. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Other Chromosomal Abnormalities Uniparental disomy –Both copies of a chromosome are inherited from a single parent –Due to error in cell division –Examples Females affected with rare X-linked disorders Prader-Willi and Angelman syndromes Fragile sites –Over 100 have been identified

23. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 6.29 Uniparental Disomy

24. Chapter 6 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fragile Sites on the Human X Chromosome Fig. 6.30