Lecture 23b Flashcards
What are Discontinuous Traits?
Traits that fall into 2 discrete categories.
“The alleles that govern these traits affect the phenotype in a qualitative way (roll your tongue)”
What type of traits is this?
Discontinuous traits
What are Quantitative Traits?
Traits that show a continuum of variation within a group of individuals.
Are the heights of students discontinuous or quantitative traits?
Quantitative, because there are more than 2 discrete categories.
“A trait that varies measurably in a given species.”
What type of trait is this?
Quantitative trait
Name 4 traits that are quantitative traits.
Anatomical traits, physiological traits, behavioral traits, and diseases.
Most quantitative traits are ___________ and exhibit a __________ of phenotypic variation.
polygenic, continuity
What is Polygenic Inheritance?
The transmission of traits that are governed by 2 or more genes.
What are Quantitative Trait Loci (QTLs)?
The locations on chromosomes that affect the outcome of quantitative traits.
T/F: Quantitative Trait Loci (QTLs) may contain one or more genes, one or many of which may affect quantitative traits.
True!
What is the reasoning that often many genes will affect quantitative traits?
There are clusters of genes which include several genes and these clusters can be in the quantitative trait loci (QTLs).
When we say most quantitative traits are polygenic, what does this mean?
Several genes can control a trait.
Who performed the first demonstration that continuous variation is related to polygenic inheritance?
Herman Nilsson-Ehle in 1909
T/F: It is possible to categorize many polygenic traits into discrete genotypic categories.
False! Many polygenic traits are difficult or impossible to categorize into discrete genotypic categories.
What are 2 instances that make polygenic traits even more difficult to categorize into categories?
- When the number of genes controlling the trait increases or 2. when the influence of the environment increases.
T/F: More genes controlling the trait = more continuous traits
True!
T/F: A Punnett square can be used to analyze most quantitative traits.
False! A Punnett square cannot be used to analyze most quantitative traits because they cannot be categorized. Instead, we must use statistical methods.
When we say that there is generally a “normal distribution” of a quantitative trait, what do we mean?
There is often a Bell Curve for the distribution of measurements of many biological characteristics. There is a cluster of measurements in the middle of the curve.
What is this the equation for? Explain the variables
This is the mean
X with the line is the mean
SX is the sum of all values in the group
N is the number of individuals/measurements total in the group.
What is this equation for? Explain the variables
What is a common way to evaluate variation within a population?
Variance
What is this the equation for? Explain the variables
Variance
Why are Variances important in the analysis of quantitative traits?
Because they are additive under certain conditions.
What can we do with the variances of genetic and environmental factors that contribute to a quantitative trait?
We can add them together to predict the total variance for that trait.
What is the Standard Deviation?
Square root of the variance
In a normal distribution, what percentage of the measurements is 1 SD? What about 2 and 3?
In a normal distribution, what is the percentage of individuals that have values more or less than 3 SDs from the mean?
Less than 0.3% of the individuals will have values that are more or less than 3 SDs from the mean.
Some statistical methods compare 2 variables to each other. When would be 3 times we would want to do this?
1) Compare the occurrence of 2 phenotypic traits
2) Compare between traits and environmental factors
3) Compare between traits and genetic relationships
What is Covariance?
Describes the degree of variation between 2 variables within a group.
T/F: Covariance is a very intuitive thing.
Covariance is not a very intuitive thing.
What is this equation? Explain the variables.
Covariance
What does the Correlation Coefficient allow for?
Allows us to determine the strength of association between 2 variables.
T/F: Correlation Coefficient is very intuitive.
True!
What is this equation for?
Correlation coefficient
