Lesson Plan : Introduction to Pedigree Analysis

Teacher Name:
 Joshua Bryan
Grade:
 College/University
Subject:
 Other

Topic:
 Pedigree analysis for organisms with small numbers of progeny in each generation and when test crosses are difficult or unethical
Content:
 Basic pedigree symbols and the relation of a pedigree to the genetic situations which cause certain traits. Vocabulary: consanguinity- mating between relatives, denoted by a double line in a pedigree siblings or sibs- offspring which are produced from the mating of the same two parents
Goals:
 Students will understand what information a pedigree displays. Students will be able to infer genetic information from a given pedigree. Students will be able to predict genotypic and phenotypic outcomes of mating within a given pedigree.
Materials:
 Attached examples of pedigrees that show dominant and recessive traits as well as X-linked traits.
Introduction:
 Genetic analysis of humans is problematic because humans have few progeny and test crosses are unethical. To gain insight into the genetics causes of specific traits or disorders that affect families.
Development:
 Presentation of the commonly used symbols on the blackboard for: male female sex unknown affected unaffected mating consanguinity twins monozygotic dizygotic stillbirth Explanation and depiction of how a pedigree is formed and how each generation is labeled with Roman numerals and each of the progeny in a generation is labeled with Arabic numerals Explanation and examples of what kind of trait is depicted. Autosomal Dominant- Males and females affected equally and every generation is affected. Autosomal Recessive- Males and females affected equally and affected individuals appear every other generation. Individuals may be affected when parents seem unaffected. X-linked Recessive- Males are affected more often than females. Affected males do not pass the trait to any sons, but all females receive 1 affected allele. Affected females pass along the trait to all sons and all daughters receive 1 affected allele. X-linked Dominant- affected males pass along trait to all daughters, but do not pass to any sons. Affected females pass along to 1/2 of all male progeny and 1/2 of all female progeny.
Practice:
 Attached pedigree of autosomal dominant and autosomal recessive conditions and how to determine risk of inheritance.
Evaluation:
 Students are asked to indicate the sex and phenotype/genotype of specific people indicated by their position in the pedigree. Students are also asked to decide which type of trait is shown in the pedigree (dominant, recessive, X-linked) and how they know. Students are then asked to predict the genotypic and phenotypic ratios of an unmarked progeny in the pedigree or the result of a hypothetical mating between two people in the pedigree.

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