Guiding Questions
Relating Mendelian Inheritance to the Behavior of Chromosomes
- Explain how the observations of cytologists and geneticists provided the basis for the chromosome theory of inheritance.
- Explain why Drosophila melanogaster is a good experimental organism for genetic studies.
- Explain why linked genes do not assort independently.
- Distinguish between parental and recombinant phenotypes.
- Explain how crossing over can unlink genes.
- Explain how Sturtevant created linkage maps.
- Define a map unit.
- Explain why Mendel did not find linkage between seed color and flower color, despite the fact that these genes are on the same chromosome.
- Explain how genetic maps are constructed for genes located far apart on a chromosome.
- Explain the effect of multiple crossovers between loci.
- Explain what additional information cytogenetic maps provide.
Sex Chromosomes
- Describe how sex is genetically determined in humans and explain the significance of the SRY gene.
- Distinguish between linked genes and sex-linked genes.
- Explain why sex-linked diseases are more common in human males.
- Describe the inheritance patterns and symptoms of color blindness, Duchenne muscular dystrophy, and hemophilia.
- Describe the process of X inactivation in female mammals. Explain how this phenomenon produces the tortoiseshell coloration in cats.
Errors and Exceptions in Chromosomal Inheritance
- Explain how nondisjunction can lead to aneuploidy.
- Define trisomy, triploidy, and polyploidy. Explain how these major chromosomal changes occur and describe possible consequences.
- Distinguish among deletions, duplications, inversions, and translocations.
- Describe the type of chromosomal alterations responsible for the following human disorders: Down syndrome, Klinefelter syndrome, extra Y, triple-X syndrome, Turner syndrome, cri du chat syndrome, and chronic myelogenous leukemia.
- Define genomic imprinting. Describe the evidence that suggests that the Igf2 gene is maternally imprinted.
- Explain why extranuclear genes are not inherited in a Mendelian fashion.
