Chapter 18

23. f (T^ET^E) = 0.685; f (T^ET^F) = 0.286; f (T^FT^F) = 0.029; f (T^E) = 0.828; f (T^F) = 0.172.

27. 1. f (A) = (2 × 42 + 24)/174 = 0.62,   

       f (G) = (2 × 21 + 24)/174 = 0.38

    2. Expected genotypic frequencies:

       f (AA) = (0.62)(0.62) = 0.384,   

       f (AG) = 2(0.62)(0.38) = 0.471,   

       f (GG) = (0.38)(0.38) = 0.144

    3. Genotype	Observed	Expected	O−E	(O−E)2	(O−E)2/E
       AA	42	33	9	81	2.45
       AG	24	41	17	289	7.05
       GG	21	13	8	64	4.92

       χ² = Σ (O − E)²/E = 14.42

       The number of degrees of freedom is the number of genotypes minus the number of alleles = 3 − 2 = 1.

       The p value is much less than 0.05; therefore, we reject the hypothesis that these genotypic frequencies may be expected from Hardy–Weinberg equilibrium.

29. 1. f (dilute color) = f (dd) = q² = 131/325 = 0.403; q = 0.635.

    2. If q = f (d) = 0.635, then p = f (D) = 1 − q = 0.365.

       f (Dd) = 2pq = 2(0.365)(0.635) = 0.464; 0.464 × 325 = 151 heterozygous cats

31. 1. 0.64 for M, 0.32 for MN, and 0.04 for N.

    2. With inbreeding, the frequencies of the M and N blood types will be higher than expected with random mating, and the frequency of the MN blood type will be lower.

32. The small population sizes and founder effects will cause strong genetic drift. The geneticists will find large variation between populations in allelic frequencies. Within populations, the same factors, coupled with inbreeding, will cause loss of genetic variation and a high degree of homozygosity.

33. The selection coefficient is 1 − fitness, so the selection coefficients for the genotypes are

    Genotype	Fitness	Selection coefficient
    ST/ST	0.47	0.53
    ST/AR	1.0	0.00
    AR/AR	0.62	0.38

    The chromosome inversions exhibit overdominance: the heterozygote has higher fitness than either homozygote. With overdominance, an equilibrium is reached, at which point the frequency of AR (q) will be

    

    The frequency of ST (p) will be 1 - q = 0.42.

34. 1. The populations raised on the ethanol-containing diet appear to be experiencing directional selection in favor of the Adh^F allele and against the Adh^S allele.

    2. In the absence of data about relative reproductive rates, we use the relative viability data as a proxy for relative fitness.

       W_FF = 0.932/1.288 = 0.724

       W_FS = 1.288/1.288 = 1.0

       W_SS = 0.596/1.288 = 0.463

36. The illustration on the left shows evolutionary change occurring gradually over time, during both periods of anagenesis and periods of cladogenesis. The illustration on the right shows evolution occurring only during cladogenesis, when one lineage splits into two.