Science and Technology In The Modern World Pedigree Practice Intro

STUDYING PEDIGREES ACTIVITY Introduction: A pedigree is a visual chart that depicts a family history or the transmission of a specific trait. They can be interesting to view and can be important tools in determining patterns of inheritance of specific traits. Pedigrees are used primarily by genetic counselors when helping couples decide to have children when there is evidence of a genetically inherited disorder in one or both families. They are also used when trying to determine the predisposition of someone to carry a hereditary disease, for example, familial breast cancer. The Components of a Pedigree: - Squares are used to indicate males in a family. - Circles are used to indicate females. - If the individual is “affected" by the trait (dominant or recessive) we darken the shape. - A line between a male and a female indicates marriage or union. - A line drawn down from the marriage line indicates offspring. - Sometimes, you will see some shapes filled in only halfway this notation indicates a hybrid (heterozygous) or carrier of the trait. - Adopted is a dotted line Twins use a connected line Female to male transgender Male to female transgender Analyzing Simple Pedigrees: A pedigree is just like a family tree except that it focuses on a specific genetic trait. A pedigree usually only shows the phenotype of each family member. With a little thought, and the hints below, you may be able to determine the genotype of each family member as well! Hints for analyzing pedigrees: - If the individual is homozygous recessive, then both parents MUST have at least one recessive allele (parents are heterozygous or homozygous recessive). If an individual shows the dominant trait, then at least one of the parents MUST have the dominant phenotype. This one will be pretty obvious when you look at the pedigree. If both parents are homozygous recessive, then ALL offspring will be homozygous recessive. NOTE: In a pedigree, the trait of interest can be dominant or recessive. The majority of harmful genetic conditions are only seen when an individual is homozygous recessive. Examples of conditions caused by recessive alleles: cystic fibrosis (a disease of the secretory glands, including those that make mucus and sweat), Falconi anemia (a blood disorder), albinism (a lack of pigmentation), and phenylketonuria (a metabolic disorder). Examples of genetic conditions caused by dominant alleles: polydactyly (presence of extra fingers), achondroplasia (a type of dwarfism), neurofibromatosis (a nervous disorder), and a disease known as familial hypercholesterolemia in which affected individuals suffer from heart disease due to abnormally high cholesterol levels Human Pedigrees For Questions 1-9, use the pedigree chart shown below. Some of the labels may be used more than once. _______ 1. A male ________ 2. A female ________ 3. A marriage ________ 4. A person who expresses the trait ________ 5. A person who does not express the trait ________ 6. A connection between parents and offspring ________ 7. How many generations are shown on this chart? Assuming the chart above is tracing the dominant trait of "White Forelock (F)" through the family. F is a tuft of white hair on the forehead. ________8. What is the most likely genotype of individual “A”? (FF, Ff or ff?) ________9. What is the most likely genotype of individual “C”? (FF, Ff or ff?) PEDIGREE PRACTICE: