A geneticist studying agriculturally important traits inanimals, designs an experiment in chickens to determine the numberof genes involved in determining the number of eggs layed permonth. A variety of chicken that lays 120 eggs per month is crossedto a variety of chicken that lays 200 eggs per month. Theiroffspring (F1 generation) lay 160 eggs per month. TheF2 egglaying phenotypes vary greatly over a range withthe highest and lowest equal to the parental extremes. A total of13,000 F2 offspring are produced with 12 laying 120 eggsper month and 13 laying 200 eggs per month.
- How many gene pairs are involved in determining the number ofeggs a chicken lays? See the last page for a tutorial oncalculating number of polygenes.
- What is the average contribution, in eggs, of each activeallele? _______________
Additional information for the polygene question.
To calculate the number of polygenes: 1/4n = ratio ofF2 individuals expressing either extreme phenotype. In the examplegiven in your textbook and mini-lecture of wheat kernel color, 1/16of the progeny were either dark red or white like the P generation.You need to solve the equation 1/4n = 1/16. n = thenumber of genes. In this example n=2, there are two genes involvedin wheat kernel color.
Determination of the Number of Polygenes (n) involved in aQuantitative Trait
n
Individuals expressing either extremephenotype
Distinct phenotypic classes
1
1/4
3
2
1/16
5
3
1/64
7
4
1/256
9
5
1/1024
11
A geneticist studying agriculturally important traits inanimals, designs an experiment in chickens to determine the numberof genes involved in determining the number of eggs layed permonth. A variety of chicken that lays 120 eggs per month is crossedto a variety of chicken that lays 200 eggs per month. Theiroffspring (F1 generation) lay 160 eggs per month. TheF2 egglaying phenotypes vary greatly over a range withthe highest and lowest equal to the parental extremes. A total of13,000 F2 offspring are produced with 12 laying 120 eggsper month and 13 laying 200 eggs per month.
- How many gene pairs are involved in determining the number ofeggs a chicken lays? See the last page for a tutorial oncalculating number of polygenes.
- What is the average contribution, in eggs, of each activeallele? _______________
Additional information for the polygene question.
To calculate the number of polygenes: 1/4n = ratio ofF2 individuals expressing either extreme phenotype. In the examplegiven in your textbook and mini-lecture of wheat kernel color, 1/16of the progeny were either dark red or white like the P generation.You need to solve the equation 1/4n = 1/16. n = thenumber of genes. In this example n=2, there are two genes involvedin wheat kernel color.
Determination of the Number of Polygenes (n) involved in aQuantitative Trait
n | Individuals expressing either extremephenotype | Distinct phenotypic classes |
1 | 1/4 | 3 |
2 | 1/16 | 5 |
3 | 1/64 | 7 |
4 | 1/256 | 9 |
5 | 1/1024 | 11 |
