Human Quantitative Traits

By: Francesco Bartucci and Adnan Sator

What are Human Quantitative Traits?

A human quantitative trait is a measureable trait that shows a continuous variation and can have numerical values that can be ordered from highest to lowest.

A continuous variation is a trait that cannot be classified into a few discrete classes.

According to the Merriam-Webster dictionary, quantitative inheritance is “genetic inheritance of a character (as color) controlled by polygenes.”

What are Human Quantitative Traits? (Continued)

As you can see, quantitative traits such as height and color resemble a bell shaped curve in a general population.

68% of a population is in the middle of a bell shaped curve.

Examples of Human Quantitative Traits

• Height• Weight• Blood Pressure• Cholesterol Level• Reading Scores• Finger Print Ridge Count• Blood Glucose Level• IQ• Etc.• (Any trait that can be ordered

from highest to lowest)

Quantitative Trait Locus—QTL

According to Cecelia M. Miles, Ph.D. & Marta Wayne, Ph.D., “Quantitative Trait Locus (QTL) analysis is a statistical method that links two types of information—phenotypic data (trait measurements) and genotypic data (usually molecular markers)—in an attempt to explain the genetic basis of variation in complex traits.”

The goal of QTL is to identify four things:

1. What the trait does

2. How it interacts with other traits

3. How many of these traits there are

4. Where exactly these traits are located

Step 1: Locate the QTL

First, find the trait to test (such as height).

Step 2: Check the Genes from Human Genome

Map

For bigger poster, there is one in Dr. Fish’s room.

Next, check the gene that is being examined from the human genome map.

Step 3: Relate the Polygene to a Function

Finally, find out what the examined gene does according to the human genome map.How does the gene affect the body?

Flipping Pennies ModelWhen flipping a penny, there is a 50/50 chance of the penny landing heads or tails. When using the Flipping Pennies Model in genetics, each penny represents one polygene for a quantitative trait.

Flipping Pennies Model (Continued)

For example, two average height parents usually have average height children.

But, it is possible for two average height parents to have very tall or short children.

Threshold EffectAccording to BusinessDictionary, the threshold effect is a “Radical change of state within a system whether a physical system like the human body or an abstract (conceptual) system such as an economy that often manifests suddenly when a critical limit is crossed.”

A qualitative trait is a trait that is either present or not present. An example of a qualitative trait is dimples: one either has dimples or one doesn’t. Qualitative traits only appear when enough genetic and environmental factors are present. Below the threshold value, the quality is not expressed.

http://www.aboutkidshealth.ca/En/HowTheBodyWorks/GeneticsIntroduction/ComplexInheritance/Pages/ThresholdEffect.aspx

But, it is possible for two parents without a certain qualitative trait to have an offspring with a qualitative trait because polygenic inheritance is the blending of polygenes.

Polygenic DiseaseAccording to MedicineNet, a polygenic disease “…is a specific disease that is caused by the combined action of more than one gene.”

Many disorders with genetic components are polygenic, including autism, cancer, diabetes, and others.

Examples of Polygenic Disease

•Diabetes•Cancer•Epilepsy•Glaucoma•Hypertension•Heart Disease•Depression•Alzheimer's Disease

Multiple Choice Question #1

1. Which is an example of a quantitative trait?

A.) Dimples

B.) Height

C.) Diabetes

D.) Hitchhiker’s Thumb

Multiple Choice Answer #1

1. Which is an example of a quantitative trait?

A.) Dimples

B.) Height

C.) Diabetes

D.) Hitchhiker’s Thumb

Multiple Choice Question #2

1. When two average height parents have children, what height is the child?

A.) Tall

B.) Average

C.) Short

D.) A, B, C, All Possible Heights

Multiple Choice Answer #2

1. When two average height parents have a child, what height will the child be?

A.) Tall

B.) Average

C.) Short

D.) A, B, C, All Possible Heights

Reference Pagehttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/Q/QTL.html

The information we attained from this website was general information on quantitative traits and two charts.

http://www.merriam-webster.com/

The information we attained from this website was the definition of quantitative trait.

http://jbiol.com/content/8/3/23

The information we attained from this website was information on polygenes and quantitative trait loci.

http://www.pnas.org/content/102/15/5310.full

The information we attained from this website was information about the threshold effect.

http://www.businessdictionary.com/definition/threshold-effect.html

The information we attained from this website was the definition of threshold effect.