Name: _________________________________ Date: _________________ Period: ______ Pedigree 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 a marriage or union. A line drawn down from the marriage line indicates offspring. Sometimes, you will see some shapes filled in only half way - this notation indicates a hybrid (heterozygous) or carrier of the trait. Mod A – Cells & Heredity Lesson 2.5 Page 20 Fry 2017 Name: _________________________________ Date: _________________ Period: ______ Pedigree Practice In humans, albinism is a recessive trait. The disorder causes a lack of pigment in the skin and hair making an albino appear very pale with white hair and pale blue eyes. This disorder also occurs in animals, a common albino found in a laboratory is the white rat. The pedigrees below trace the inheritance of the allele that causes albinism. 1. Given the following genotypes, describe the phenotypes (normal or albino). AA = ________________________________ Aa = ________________________________ aa = ________________________________ Fill out the blanks on the pedigree to the right. 1. How many children does this family have? _______ 2. What are the sexes of the children? _______ Fill out the blanks of the pedigree to the right (AA, Aa, aa). 3. How many children does the original couple have? _______ 4. How many grandchildren? _______ Mod A – Cells & Heredity Lesson 2.5 Page 21 Fry 2017 Name: _________________________________ Date: _________________ Period: ______ Fill out the blanks of the pedigree to the right (AA, Aa, or aa). 5. How many children does the original couple have? _______ 6. How many grandchildren does the original couple have? _______ 7. What is the sex of the grandchild? _______ Rats can produce a lot more offspring than humans, making a pedigree more difficult to manage. A researcher has four female white rats named April, May, June, and July. One night, the cage was left open in the lab and a brown rat got into the female's cage. Six weeks later, the rats had litters of babies of varying colors. Two of the offspring managed to reproduce before the researcher was able to sort out the mess. The researcher decided to make a pedigree to determine the genotypes of the offspring, but he couldn't quite remember how to make one. The image below shows his pedigree, can you determine the rats’ genotypes ? Mod A – Cells & Heredity Lesson 2.5 Page 22 Fry 2017 Name: _________________________________ Date: _________________ Period: ______ Gray gray 8. How many carriers of color blindness are in the pedigree above? _______ 9. What gender are all of the carriers? _____________________________ 10. Explain why only one gender is able to be a carrier for a sex-linked disorder such as colorblindness. _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ Mod A – Cells & Heredity Lesson 2.5 Page 23 Fry 2017 .