WK 7B

Question 1

Continuous trait (quantitative):

Answer 1

A trait that can take on a potentially infinite number of states over a continuous range, such as height, or skin color in humans. Continuous traits typically have complex inheritance involving multiple genes (that act additively) plus environmental factors.
traits that can take up a continuous range of values, have a maximum and minimum with a bell curve shaped distribution

Question 2

Discrete or discontinuous trait (qualitative)

Answer 2

trait occurs in distinct categories
Mendel’s peas – yellow or green, classified into categories, simple Mendelian genetic inheritance

Question 3

Categorical trait:

Answer 3

A trait for which individuals can be sorted into discrete or discontinuous groupings, such as presence or absence of disease*. Categorical traits often exhibit simple inheritance (Mendelian ratios observed in progeny).

Question 4

Threshold traits

Answer 4

are categorical traits (affected vs unaffected) with underlying continuous variation for which the expression of the different phenotypic states depends on a combination of multiple genetic and/or environmental factors that place an individual above or below a critical value (threshold) for trait expression.
categorical traits but more complex, example is diabetes (either have it or not, but more details based on risk factors)

Question 5

Meristic traits (counting traits):

Answer 5

quantitative, but they are restricted to certain discrete values.They do not take on a continuous range of values. Meristic traits usually have complex inheritance.
also quantitative, integer values, cannot be anything in between, not continuous

Question 6

complex trait

Answer 6

is any trait that does not show simple Mendelian inheritance.
Complex traits do not behave in simple Mendelian fashion, but instead have a continuous range of variation.
Interaction of several genes affecting a metric trait could produce a bell-shaped curve.Interacting genes underlying hereditary continuous variation are called polygenes, or QTLs (quantitative trait loci)

Question 7

Polygenic traits

Answer 7

result from the influence of multiple genes.
Polygenes for a particular trait are distributed throughout the genome on different chromosomes and show independent assortment.Variation and assortment of polygenes can contribute to continuous variation in a population.
polygenes → genes that affect height, some pull you up and some push you down, lots of genes control a trait, inherited independently through Mendelian inheritance

Question 8

Multifactorial hypothesis (Fisher, 1918)

Answer 8

Multifactorial traits are the result of a set of interactions among multiple Mendelian genes (each with a small effect on the trait) and various environmental factors.

Question 9

Effects of environmental factors on phenotypic variation

Answer 9

With increased environmental effect, some variation in phenotype and some overlap
Example could be weight, could have twins which have completely different weights if they have different lifestyles

Question 10

Empiric risk

Answer 10

used to predict chance of multifactorial (complex) trait occurring in an individual
Likelihood that a hereditary trait or disorder present in one family member will occur again in other family members
Population statistic based on observation of families with hereditary trait

Question 11

Incidence

Answer 11

proportion of persons who develop a condition during a particular time period (/year) → new cases

Question 12

Prevalence

Answer 12

proportion of persons who have a condition at a particular time period