Name: _____________________________________ Date: _________________ Block: __________ Exploring Autosomal Pedigrees You can look at a pedigree and determine whether traits are dominant or recessive, and you can also tell if it is sex-linked or autosomal. Sex-linked traits are carried on the sex chromosomes (X or Y). Autosomal traits are carried on chromosomes 1 to 22. Use the guided steps below to unveil the patterns in pedigrees. In the pedigree below, we will explore the autosomal trait for dimples. Having no dimples is dominant to having dimples. A. Interpreting a Pedigree 1. Number all individuals on the pedigree at the top of each circle or square. I 2. In a pedigree, a square represents a male. If is it darkened he has dimples. If the square is open, he does not have dimples. II a. How many males are there? _______________ 1 2 III b. How many males have dimples? ____________ 3. A circle represents a female. If it is darkened she has dimples. If it is open, she does not have dimples. IV a. How many females are there? ______________ b. How many females have dimples? ___________ 4. A marriage is indicated by a horizontal line connecting a circle to a square. a. How many marriages are there? _____________ 5. A line perpendicular to a marriage line indicates the offspring. If the line ends with either a circle of a square, the couple had only one child. However, is the line is connected to another horizontal line, then several children were produced, each indicated by a short vertical line connected to the horizontal line. The first-born child appears to the left and the last-born child appears to the right. a. How many children did the first couple have (couple in row I)? _____________________________ b. How many children did the third couple have (couple in row III)? ___________________________ 6. Level I represents the first generation and level II represents the second generation. a. How many generations are there? _____________ b. How many members are there in the fourth generation? ______________ B. Determining the Pattern of Inheritance and Assigning Genotypes When working through a pedigree, you must determine whether the trait (the shaded shapes) is dominant or recessive. This involves the “guess and check” method. With no other information aside from the pedigree, you may find that the trait could be passed BOTH ways. Choose a letter (let’s use A) and begin assigning genotypes. Remember that they recessive individuals must be homozygous. Complete the legend for the following pedigree regarding fur color in mice. All of the shaded shapes represent black fur color. All of the open shapes represent white fur color. = = = = Let’s start by testing whether or not black fur color is inherited as a DOMINANT trait (AA or Aa). Label each individual. If all genotypes can be labeled, the trait is inherited that way. You may have indivudals that you cannot tell (nor does it matter) whether they are AA or Aa. In this case, label them as (A-) (Hint: You will have 3 (A-)s in the pedigree below.) Fur Color in Mice 1. Is black fur color a dominant trait? ________________________ Let’s try it again, but check and see if black fur can also be a recessive trait (aa). 2. Is black fur color a recessive trait? ___________________________ Still not quite sure about how to label genotypes? Search for the following video on YouTube, Pedigree Analysis 1: How to solve a genetic pedigree No. 1. It is By Andrew Douch and should be 9:13 minutes long. Start at MINUTE 5. He works through sex-linked options as well, but you are not responsible for knowing this. This video will work on your cell phone. C. Create Your Own Pedigree In the space below, use colored pencils to create a pedigree with the following information. Follow the guidelines for a pedigree when creating your own. Ray and Elaine were married in 1970. They both have straight hair. Straight hair is the dominant allele over curly hair. Ray and Elaine had 2 daughters and then a son. The first born daughter, Candace, has curly hair. The second born daughter, Judy, has straight hair. Neither daughter is married yet or has children. The son, Mike, has curly hair. Mike married Alisha, who has straight hair. They had 2 children of their own, first Greg then Nicole. Both Nicole and Greg have straight hair. Create a pedigree. Label the names and genotypes for each individual. Use the following key to color your pedigree: Red = Curly Hair White = Straight Hair Blue = Heterozygote Green = Unknown Genotype