1. Chromosome Disorders

2. Classification of genetic disorders  Single-gene disorders (2%)  Chromosome disorders (<1%)  Multifactorial disorders (60%)

3. Types of Mutation class of mutation mechanismfrequencyexamples Genomechromosome missegregation 10 -2 / cell division aneuploidy Chromosomechromosome rearrangement 10 -4 / cell division trans- locations Genebase-pair mutation 10 -10 / cell division point mutations

4. Chromosome disorders accounting for about half of all spontaneous first-trimester abortions affecting about 1% liveborn infants Chromosome Mutation Genome Mutation

5. Chromosome Mutation abnormalities of chromosome structure Unbalanced rearrangements (sick) deletions, duplications Balanced rearrangements (healthy) inversions, translocations

6. Unbalanced rearrangements

9. Balanced rearrangements

13. Genome Mutation abnormalities of chromosome number due to nondisjunction (chance occurrence) euploid – an exact multiple of the haploid chromosome number Aneuploidy – trisomy, monosomy Polyploidy – triploid (3n), tetraploid (4n)

16. Down syndrome (ultrasound examination)

17. Down syndrome

19. Turner syndrome

22. Klinefelter syndrome

25. Literature Biology, eighth edition, Campbell, Reece Unit three: Genetics Chapter 15: The Chromosomal Basis of Inheritance Concept 15.4: Alterations of chromosome number or structure cause some genetic disorders Pages 297 – 300