The Chromosomal Basis of Inheritance
 

1. How did the discovery of sex-linked genes support the chromosomal theory of inheritance?
2. What do we mean by linked genes?  How and why do the results of genetic crosses involving linked genes deviate from those expected according to Mendel’s Law of Independent Assortment?
3. How is independent assortment responsible for genetic recombination in unlinked genes?  How is crossing over during meiosis responsible for genetic recombination in linked genes?
4. Be able to calculate the recombination frequency in a dihybrid test cross.  How do the results of these crosses allow us to construct a linkage map of a chromosomes genetic loci?
5. What is a map unit?  Given the recombination frequency between several genes on a chromosome, be able to construct a linkage map.  How is a linkage map different from a cytological map?
6. What are some other modes of sex determination?
7. How are the patterns of inheritance of sex linked (X – linked) traits different from traits determined by genes located on autosomes?
8. What are some common sex linked disorders in humans?
9. What is X – inactivation and how does it result in the presence of a Barr Body?  Why can X-inactivation result in females that consist of a mosaic of different cell types?
10. How can nondisjunction of chromosomes result in aneuploidy?   What is the difference between a monosomic and a trisomic aneuploid cell?
11. How does a polyploid (triploid or tetraploid) cell result?
12. How do deletions, duplications, inversions, and translocations alter the structure of a chromosome?
13. What are some common human disorders that result from alterations in chromosome number and structure?
14. Where else are genes located in eukaryotes other than on chromosomes in the nucleus of the cell? How are extranuclear genes inherited?
15. Using a pedigree, be able to determine the inheritance pattern (autosomal, sex linked, dominant, recessive etc…) for a given trait or disorder.