2. Three Point Mapping: Forward Analysis
Single Crossovers Region I (SCO I)
jv se+ h+
jv+ se h
6.8 m.u.
0.5 m.u. jv se h
jv+
se+ h+
Region: I II
Single Crossovers Region II (SCO II)
jv se h+
jv+ se+ h
Double Crossovers (DCO)
jv se+ h
jv+ se h+
Prob(XO in Region I) = 0.068
Prob(XO in Region II) = 0.005
Prob(XOs in Region I and II) =
No Crossovers, Parental (NCO)
jv se h
jv+ se+ h+
(0.068) x (0.005) =

3. Three Point Mapping: Forward Analysis
Prob(DCO) = (0.068) x (0.005) =
Prob(SCO I) = =
Prob(SCO II) = =
Prob(NCO) =
1 - Prob(SCO I) - Prob(SCO II) - Prob(DCO) =
6.8 m.u.
0.5 m.u. jv se h
jv+
se+ h+
Region: I II
Double Crossovers (DCO)
jv se+ h
jv+ se h+
Single Crossovers Region I (SCO I)
jv se+ h+
jv+ se h
Single Crossovers Region II (SCO II)
jv se h+
jv+ se+ h
No Crossovers, Parentals (NCO)
jv se h
jv+ se+ h+

4. Penetrance and Expressivity
Penetrance: in a population of individuals with the same genotype, the percentage who exhibit the phenotype for that genotype
Expressivity: for a given genotype, the degree to which the phenotype is expressed

5. Refer to Figure 6-22, Griffiths et al., 2015.

6. Piebald Spotting In Beagles
Every individual shown has the same genotype for this gene.
Refer to Figure 6-23, Griffiths et al., 2015.

7. Vulcan phenotypes for all three characters?
Problem 60 Chpt 4 (p. 170, Griffiths et al., 2015):
Vulcans have pointed ears (determined by allele P), absent adrenals (determined by A), and right-sided heart (determined by R). All these alleles are dominant to normal Earth alleles: rounded ears (p), present adrenals (a), and left-sided heart (r). The three loci are autosomal and linked as shown in this linkage map:
Mr. Spock, first officer of the starship Enterprise, has a Vulcan father and an Earthling mother. If Mr. Spock marries an Earth woman and there is no (genetic) interference, what proportion of their children will have:
Vulcan phenotypes for all three characters?
Earth phenotypes for all three characters?
Vulcan ears and heart but Earth adrenals?
d. Vulcan ears but Earth heart and adrenals?
P A R
10 m.u m.u.

8. 1: b – a – c 2: b – a – c 3: b – a – c 4: a – c – b 5: a – c – b
Problem 58 Chpt 4 (p. 170, Griffiths et al., 2015):
The five sets of data given in the following table represent the results of testcrosses using parents with the same alleles but different combinations. Determine the order of genes by inspection – that is, without calculating recombination values. Recessive phenotypes are symbolized by lowercase letters and dominant phenotypes are plusses.
Data Set : Gene Order
1: b – a – c
2: b – a – c
3: b – a – c
4: a – c – b
5: a – c – b