Chapter 27, Problem 1CONQ

Give several examples of quantitative traits. How are these quantitative traits described within groups of individuals?

Summary Introduction

To review:

The examples of quantitative traits and their estimation in the group of individuals constituting a population.

Introduction:

Complex traits are the traits that are influenced by many genes and environmental factors as well. The branch of genetics that studies both complex and quantitative traits is called Quantitative genetics. These traits have proved highly beneficial to study human diseases, like diabetes, and for the betterment of agriculture. Example, traits like fruit size, adaptability of a crop towards the environmental conditions, height and length of the crop, and its yield are all governed by Quantitative trait loci (QTLs).

Explanation of Solution

Quantitative traits are the traits that are numerically determined. These are an example of complex traits. In humans, quantitative traits include weight and height, nose shape, rate of metabolism of food. These traits are determined by QTLs. QTLs are defined as the regions on the chromosome containing genes that influence the outcome of quantitative traits.

Examples of quantitative traits are as follows:

Anatomical traits- Weight, height of an individual, number of bristles present in Drosophila.

Behavioral traits- Photoperiodism and calls for mating.

Diseases- Hypertension and diabetes.

Physiological traits- Speed of flight and running and rate at which the food metabolizes.

Within the group of individuals constituting a population, quantitative traits are determined by Mean, Variance, and Standard deviation.

Mean- It is one of the statistical methods that describe quantitative traits. It given as the summation of the observation to the total count of the observations made.

$\overline{X}$= $\frac{{\displaystyle \sum X}}{N}$

Where, ${\displaystyle \sum X}$= Sum of all observations

$N$= Number of observations

$\overline{X}$= Mean

Variation in a population can also be determined by using another statistical method called Variance. Variance is defined as the variation around the mean.

$Vx$ = $V_x=\frac{{\displaystyle \sum _{}^{}fi{(X_i-\overline{X})}^2}}{N-1}$

Where, V_x is Variance

${\displaystyle \sum _{}^{}fi{(X_i-\overline{X})}^2}$ issummation and square of difference in between each value and mean

N is Number of observations

Standard deviation (SD) is another statistical method for the measurement of quantitative traits in the population. It is defined as square root of variance.

$\text{SD}=\sqrt{\text{Vx}}$

Conclusion

Therefore, it can be concluded that Quantitative traits are numerically determined, for example, height, weight, number of bristles in Drosophila and photoperiodism. Estimation of quantitative traits in a population is carried through mean, variance and standard deviation.