index
Link to the Univeristy of British Columbia index
Biology 334 course outline textbook assessment tutorials lecture notes
Biol 334 HomePage Biology 334 people Biology 334 course outline

 

 

 

Biology 334

Proof of the Perkins Formula

We will assume that the only possible meioses are those with:

no crossover (NCO), a single crossover (SCO), or double crossovers (DCO).

From Fig 4-18 we see that the 6 meioses shown result in PD, T, PD, T, T and NPD asci

(in that order from top to bottom).

NPD represent 1/4 of all DCO, therefore DCO = 4 NPD

The mean # crossovers by definition      = SCO + 2 x DCO

From Fig 4-18 we see that                         SCO can be estimated as T – 2NPD  and

                                                                    DCO can be estimated as 4 x NPD

Hence mean # crossovers                       = T – 2NPD  +  2(4 x NPD)

                                                                = T + 6NPD

Since any number of crossovers on average produce a RF of 50%

The corrected map distance =  50(T + 6NPD)   [The Perkins Formula]

 

 

index 334 HomePage index 334 People index 334 Course outline index Textbook index Assessment index Tutorials index 334 Lectures index

Google
%(domain)s %(domain)s %(domain)s

© copyright 2004 Univerisity of British Columbia     webmaster craigber@interchange.ubc.ca