Suppose the mature height of a plant is a multifactorial trait un...

Question

Suppose the mature height of a plant is a multifactorial trait under the control of five independently assorting genes, designated A, B, C, D, and E, and five environmental factors. There are two alleles of each gene (A₁, A₂, etc.). Each allele with a subscript 1 (i.e., A₁) contributes 5 cm to potential plant height, and each allele with a 2 subscript (i.e., A₂, etc.) contributes 10 cm to potential plant height. In other words, a genotype containing only 1 alleles (A₁A₁B₁B₁C₁C₁D₁D₁E₁E₁) would have a potential height of [(10)(5)]=50 cm, and a genotype with only 2 alleles (A₂A₂B₂B₂C₂C₂D₂D₂E₂E₂) would have a potential height of [(10)(10)]=100 cm.
The five environmental factors are (1) amount of water, (2) amount of sunlight, (3) soil drainage, (4) nutrient content of soil, and (5) temperature. Each environmental factor can vary from optimal to poor. If all factors are optimal, assume that full potential height is attained. However, if one or more of the environmental factors is less than optimal, then height is reduced. The state of each environmental factor has an effect on growth. In this exercise, we'll assume that the growth is affected according to the following scale:

Environmental Factor State Height Lost
Optimal (O)   0 cm
Good (G)   4 cm
Fair (F)   8 cm
Marginal (M) 12 cm
Poor (P) 16 cm

Thus, for example, if one environmental factor is optimal, two are good, one is fair, and one is marginal, the loss of potential height is . If the loss of height potential is greater than the height potential of the plant, the plant does not survive.

Calculate the potential height, based on inherited alleles, and the attained height, based on growth in the environmental circumstances given, for the three plants (a, b, and c) in the accompanying table.

Accepted Answer

Hi, everybody. Let's look at our next problem. Suppose the color of a flower is a multifactorial trait controlled by three independently assorting genes. Each with two alleys, each alley with a subscript. One contributes two units of color and each all with a two subscript. For example, a two contributes four units of color. The presence of a particular type of nutrient in the soil also affects flower color. There are three possible states for the nutrient content of the soil. Optimal, moderate and poor. If the nutrient content is optimal, the flower achieves its full color potential. However, if the nutrient content is moderate or poor, the flower loses color potential, the degree of color loss depends on the nutrient state as follows. And there's a table saying nutrient state on the left and color loss on the right. Optimal zero units, moderate three units poor six units. Suppose a flower has the genotype A one A two B one B, two C one C two and all those numbers there are subscripts and is grown in soil with moderate nutrient content. What is the attained color of the flower based on its growth in the given environmental circumstances choice. A 15, B, 18 C, 12 or D, 21. Well, we've got a really long problem here with a lot of information but it's pretty straightforward when we think it through, we have our three different genes and two alleys for each one. Our flower genotype is heterozygous for each gene A B and C. In each case, it has type one and type two, all one of each for each gene. And we know that if the subscript is one, so if the all is type one, we'll call it, then the flower gets two units of color. And type two, the flower gets four units of color. So first, we have to calculate how many units of color the flower will inherit based on its genotype. We then look at the environmental effect of the soil it's grown in, we're told that it grows in moderate nutrient content and we can look at our table and see that moderate nutrient content results in three units of color loss. So we're going to need to calculate the color potential essentially based on the genotype and subtract the color loss. That's a result of the environment. So we have one each for three different genes of the type one, all and one each for three different genes of the type two. So we have three of each. So we have three multiplied by two units. And that would be the contribution from our three type one allys added to three, multiplied by four units are three type two alleys and that will equal six units plus units are added to 12 units which equals 18 units that would be based on the genotype. Now we look back at soil condition. So we have 18 units based on the genotype minus sign, three units based on the moderate soil content. And that will equal 15 units total or 15 color units that are flower inherits and expresses based on the soil condition. So that would be choice a 15 as our correct answer. See you in the next video.

Key Concepts

Multifactorial Traits

Genotype and Phenotype

Environmental Impact on Growth

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