1. Recombinants are produced by crossovers.

2. Map distances are generally additive.

3. Longer regions have more crossovers and thus higher recombinant frequencies.

4. Independent assortment produces 50% recombinants.

5. For linked genes, recombinant frequencies are less than 50%.

6. 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) =

7. 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+