5.4.12: Chapter 6 Answers

Chapter 6 Answers

1. 1. These are four common terms that are often used interchangeably by novice students, but do have distinctly different meanings and uses.
      1. gene = general term for a segment of nucleic acid that is responsible for one or more phenotypes
      2. locus = the position of a gene along a chromosome,
      3. allele = the form (DNA sequence) of a gene at a locus,
      4. transcription unit = the segment of DNA that is transcribed into RNA (often mRNA in the case of a protein coding gene).
   2. Form (1) RR (red) x rr (white) gives Rr (red progeny). “R” is dominant to “r”. Form (2) r+r+ (red) x r-r- (white) gives r+r- (red progeny). “r+” is dominant to “r-”. For pink progeny, the symbols are the same, only “R” or “r+” is semi-dominant to “r” or “r-”.
   3. If your blood type is B, then your genotype is either I^Bi or I^BI^B. If your genotype is I^Bi, then your parents could be any combination of genotypes, as long as one parent had at least one i allele, and the other parent had at least one I^B If your genotype was I^B I^B, then both parents would have to have at least one I^B allele.
   4. case 1 co-dominance; case 2 incomplete-dominance; case 3 incomplete penetrance; case 4 pleiotropy; case 5 haplo-sufficiency; case 6 haplo-insufficiency; case 7 broad (variable) expressivity
   5. • Mutant#1 = hypomorph;
      • Mutant#2 = hypermorph;
      • Mutant#3 = amorph;
      • Mutant#4 = neomorph;
      • Mutant#5 = antimorph