Concepts - Part III
Chromosome Versus Maximum Equational Segregation.
| Genotype |
Chromosome |
Maximum
Equational (a =1/6) |
| Simplex |
1/2Aa:1/2aa |
1/24AA:10/24Aa:13/24aa |
| Duplex |
1/6AA:4/6Aa:1/6aa |
4/18AA:10/18Aa:4/18aa |
| Triplex |
1/2AA:1/2Aa |
13/24AA:10/24Aa:1/24aa |
Determination of gametic segregation ratio for Triplex.
The probability of double reduction gametes is a.
The probability of non-double reduction gametes is 1-a.
There are four types of double reduction gametes and
six combinations of non-double reduction gametes. a+1-a=1.
| Double-reduction
game |
Non-double
reduction |
| Combin |
from
triplex |
Prob. |
Combination |
From
Triplex |
Prob. |
| a1a1 |
AA |
a/4 |
a1a2 |
AA |
(1-a)/6 |
| a2a2 |
AA |
a/4 |
a1a3 |
AA |
(1-a)/6 |
| a3a3 |
AA |
a/4 |
a1a4 |
Aa |
(1-a)/6 |
| a4a4 |
aa |
a/4 |
a2a3 |
AA |
(1-a)/6 |
| Total |
a |
a2a4 |
Aa |
(1-a)/6 |
| a3a4 |
Aa |
(1-a)/6 |
| Total |
1-a |
We can collect like gametes based on similar genotype, regardless
of whether they come from double reduction or otherwise.
| Gamete
Genotype |
Probability |
| AA |
3(a/4)
+ 3/6(1-a) = 1/4(2+a) |
| Aa |
3/6(1-a)
= 1/2(1-a) |
| aa |
a/4
= a/4 |
| Total |
a
+ 1 - a = 1 |
The above table agrees with the triplex gamete ratio
on the bottom of pg. 7
