QUESTION 10 In a cross of two purebreeding lines of oranges

QUESTION 10

In a cross of two pure-breeding lines of oranges producing different fruit sizes, the variance in grams  (g)   of fruit weight in the  F1  is 4.7  g , and the variance among the  F2  is 5.3  g . Express all answers to 2 places after the decimal point. For example, 1.23.

Assuming the environment doesn\'t change between generations, determine the environmental variance V   for the trait.

Determine the genetic variance VG  for the trait.

Determine the broad sense heritability of the trait.

Solution

Ans:

Vp = Vg + Ve

two pure bredding lines are crossed

i.e an AA is crossed with aa

  
i am assuming it to be a cross between AA and aa

asssuming the two pure bred plants to be of different genotypes

AA x aa

F1 Aa

now all the genotypes are Aa

so there is no genotypic variance in F1

i.e for F1 - Vg= 0

Vp = Vg + Ve

4.70 = 0 + Ve

Ve= 4.70g

now this Ve should remain the same in F2 too

assuming ideal conditions and the environment not changing



in F2

Vp = Vg + Ve

5.3= Vg+ 4.7

Vg= 0.6 g


broad sense heritability= Vg/Vp

= 0.6/5.3

= 0.11

Ans a : Vp = Vg + Ve, Vp= 5.3, Ve = 4.7, 5.3-4.7=0.6

Ans b : because pure breeding F1, Vg of F1 is 0. Ve+Vg= Vp Vp= 4.7 (given F1) Ve+0 = 4.7, so Ve= 4.7

Ans c : Vp= 5.3, Ve = 4.7,

Broad sense Vg/Vp = 0.6/5.3=0.11