Chapter 24 Flashcards
Phenotypes fall on a range without clear division: quantitative, continuous. Why are they called continuous?
- exhibit a spectrum of possible values
- trait can vary smoothly across a continuum than falling into distinct categories
Why is the relationship of phenotype to genotype complex?
What type of inheritance does this contribute to?
- due to multiple genes/loci
- polygenic inheritance
What is the unabbreviated version of QTL?
quantitative trait loci
What strongly influences multifactorial characteristics?
- loci
- environment
What does meristic mean?
- whole numbers
- traits that are countable and can’t be continuous
Define threshold characteristics?
- two phenotypes
- underlying quantitative inheritance (disease susceptibility)
What does it mean when alleles are additive at all loci?
- for every gene involved in a trait, each allele contributes a predictable amount to the overall phenotype
- no interaction between alleles at different loci
Give an example of “additive, but not equal”
A+A+B-B- = A-A-B+B+
A+A+ does not = B+B+
Can environmental influences make characteristics more continuous?
yes
What does a normal distribution curve look like?
- a simple hill
- “bell-shaped”
What does a skewed distribution curve look like?
large hill, then decrease in hill height
What does a bimodal distribution curve look like?
- two hills
- one large, one medium
For normal distribution, what is the “mean”?
What’s its unit?
- average
- (line over) X
What is standard deviation (s)?
- calculated from the variance
- measuremnet of how far the typical individual is from the mean
What does it mean when the value are high for standard deviation?
Low?
high:
- wide curve
low:
- narrow curve