Question

This pedigree chart tracks the inheritance of a recessive trait that is not sex-linked. Based on the information in the chart, which of the following statements is true?

This pedigree chart shows three generations. The individuals are numbered from left to right, starting at the top left of the chart. Squares represent males and circles represent females. If the symbol is gray, that individual exhibits the recessive trait. If the symbol is white, the individual exhibits the dominant trait. On the first row there are two couples mated together. The first couple is made up of individuals #1 (recessive) and #2 (dominant). They have four offspring on the second row that all exhibit dominant traits: #5 (dominant), #6 (dominant), #7 (dominant), and #8 (dominant). The second couple in Generation #1 is made up of individual #3 (dominant) and individual #4 (dominant). They have three offspring in Generation 2: #9 (dominant), #10 (recessive), and #11 (dominant). Individual #8 from the first family and individual #9 from the second family mated together and produced three offspring in Generation 3. These offspring are #12 (recessive), #13 (dominant), and #14 (recessive).

Individual #8 must be heterozygous for the trait.
Individual #10 must be heterozygous for the trait.
Individual #13 must be homozygous dominant.
Individual #3 must be homozygous dominant.

Answer 1

Picture for better understanding

Answer 2

Thoughts?

If offspring 12 and 14 are both homozygous recessive, they must have inherited one recessive allele from each parent. What does that tell you about their dominant parents 8 and 9?

Answer 3

Good, so 8 must be heterozygous which means Answer choice A is correct

Offspring 13 **can** be heterozygous *or* homozygous dominant depending on whether it inherits a recessive allele or not, which is why C doesn’t work.