5.4.11: Chapter 6 Study Questions

Chapter 6 Study Questions

1. Distinguish among the following terms: (1) gene, (2) locus, (3) allele, (4) transcription unit.
2. A flower geneticist crosses a red flowered diploid plant with a white flower diploid plant and all the progeny are red. Use two different forms of symbols to show this cross and its progeny. What if all the progeny were pink?
3. If your blood type is B, what are the possible genotypes of your parents at the locus that controls the ABO blood types?
4. In the table below, match the mouse hair colour phenotypes with the term from the list that best explains the observed phenotype, given the genotypes shown. In this case, the allele symbols do not imply anything about the dominance relationships between the alleles.
   List of terms: haplo-sufficiency, haplo-insufficiency, pleiotropy, incomplete dominance, co-dominance, incomplete penetrance, broad (variable) expressivity.

   Case	A1A1	A1A2	A2A2
   1	all hairs black	on the same individual: 50% of hairs are all black and 50% of hairs are all white	all hairs white
   2	all hairs black	all hairs are the same shade of grey	all hairs white
   3	all hairs black	all hairs black	50% of individuals have all white hairs and 50% of individuals have all black hairs
   4	all hairs black	all hairs black	mice have no hair
   5	all hairs black	all hairs white	all hairs white
   6	all hairs black	all hairs black	all hairs white
   7	all hairs black	all hairs black	hairs are a wide range of shades of grey

5. In this hypothetical example of Drosophila bristle mutations, when various, true-breeding mutant strains (all at a single locus) are crossed to a wild type strain the following phenotypes are observed in the progeny:
   • Mutant#1 = bristles 20% shorter
   • Mutant#2 = bristles 30% longer
   • Mutant#3 = bristles 50% shorter
   • Mutant#4 = bristles kinked and misshapen
   • Mutant#5 = bristles are missing

   What is the best characterization, using Muller’s Morphs, for each?