# 5: Pedigrees and Populations

[ "article:topic-guide", "authorname:tnickle", "Pedigree" ]

The basic concepts of genetics described in the preceding chapters can be applied to almost any eukaryotic organism. However, some techniques, such as test crosses, can only be performed with model organisms or other species that can be experimentally manipulated. To study the inheritance patterns of genes in humans and other species for which controlled matings are not possible, geneticists use the analysis of pedigrees and populations.

• 5.0: Prelude to Pedigrees and Populations
To study the inheritance patterns of genes in humans and other species for which controlled matings are not possible, geneticists use the analysis of pedigrees and populations.
• 5.1: Pedigree Analysis
Pedigree charts are diagrams that show the phenotypes and/or genotypes for a particular organism and its ancestors. While commonly used in human families to track genetic diseases, they can be used for any species and any inherited trait.
• 5.2: Inferring the Mode of Inheritance
Given a pedigree of an uncharacterized disease or trait, one of the first tasks is to determine which modes of inheritance are possible and then which mode of inheritance is most likely. This information is essential in calculating the probability that the trait will be inherited in any future offspring. We will mostly consider five major types of inheritance: autosomal dominant (AD), autosomal recessive (AR), X-linked dominant (XD), X-linked recessive (XR), and Y-linked (Y).
• 5.3: Sporadic and Non-Heritable Diseases
Many diseases that have a heritable component, have more complex inheritance patterns due to (1) the involvement of multiple genes, and/or (2) environmental factors.
• 5.4: Calculating Probabilities
Probabilities in pedigrees are calculated using knowledge of Mendelian inheritance and the same basic methods as are used in other fields. The first formula is the product rule: the joint probability of two independent events is the product of their individual probabilities; this is the probability of one event AND another event occurring.
• 5.5: Population Genetics
A population is a large group of individuals of the same species, who are capable of mating with each other. It is useful to know the frequency of particular alleles within a population, since this information can be used to calculate disease risks. Population genetics is also important in ecology and evolution, since changes in allele frequencies may be associated with migration or natural selection.
• 5.E: Pedigrees and Populations (Exercises)
These are homework exercises to accompany Nickle and Barrette-Ng's "Online Open Genetics" TextMap.
• 5.S: Pedigrees and Populations (Summary)