11: Pedigrees and Populations
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.
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- 11.1: Prelude to Pedigrees and Populations
- This page discusses how geneticists use pedigree analysis to study inheritance patterns of genes in humans and other species, particularly when controlled mating is not possible. It highlights the example of polydactyly, a condition with six fingers, as a case for examination through these methods.
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- 11.2: Pedigree Analysis
- This page discusses pedigree charts, which are diagrams that show the phenotypes or genotypes of an organism and its ancestors to track genetic diseases within families. They utilize standardized symbols to represent sex, relationships, and traits, helping geneticists analyze inheritance patterns and disease probabilities. Accuracy is vital, but errors can occur from family memories or clinical diagnoses.
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- 11.3: Inferring the Mode of Inheritance
- This page outlines five modes of inheritance for genetic traits: autosomal dominant (AD), autosomal recessive (AR), X-linked dominant (XD), X-linked recessive (XR), and Y-linked (Y). AD traits require one affected parent and appear in each generation, whereas AR traits need both parents to carry the allele and can skip generations. XD traits primarily affect females, XR traits mainly affect males, and Y-linked traits occur only in males.
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- 11.4: Sporadic and Non-Heritable Diseases
- This page discusses the complexity of human traits and diseases, highlighting that they are not solely caused by single gene mutations but also influenced by multiple genes and environmental factors. It notes that non-genetic diseases can appear heritable due to family environmental influences.
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- 11.5: Calculating Probabilities
- This page explains how to deduce genotypes from phenotypes in a pedigree, focusing on disease inheritance. It utilizes Mendelian genetics to calculate genotype probabilities through product and sum rules, exemplified by the likelihood of two heterozygous carriers of an autosomal recessive disease having an affected child. The text includes a pedigree illustration to estimate probabilities for individuals based on familial connections and genotypic assumptions.
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- 11.6: 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.
Contributors
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Dr. Todd Nickle and Isabelle Barrette-Ng (Mount Royal University) The content on this page is licensed under CC SA 3.0 licensing guidelines.