Question

Procedure 8.5 PEDIGREE CHARTS Pedigree charts are diagrams that illustrate how a trait is inherited through generations of a family. They can help us determine genotypes and patterns of inheritance for a trait. HOW TO READ A PEDIGREE CHART 1. Look at the sample pedigree chart in Figure 8.7. 2. Square boxes represent males and circles represent females. 3. A filled-in figure means that the trait is present in that individual. An empty figure means the trait is not present. 4. Each row represents a generation, indicated by Roman numerals down the right side of the diagram. Each individual is also numbered. We can refer to a single individual by generation and row number. For example, Il-3 is the third person from the left in generation II. 5. Two figures connected by a direct horizontal line are married. Their children are indicated by vertical lines descending from the horizontal line. WOOOOOOOOOOOOOo33UUUUUUUUU bluedoor, LLC Figure 8.7: Pedigree chart for widow's peak. Determining Genotype Using Phenotype In this procedure, we will determine genotypes using the phenotype of each individual. We know from our previous exercise that widow's peak is controlled by a single gene and there are only two alleles (W or w). We also know that widow's peak is a dominant trait. 1. Each person with a widow's peak has a filled-in figure in Figure 8.7. Write a single "W" under each filled-in figure. You will have to wait to determine the second allele. 166 Genetics Laboratory 8
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Answer 1

Ans 1: IV-1 has an unknown genotype.

Ans 2: II-2, II-3, III-1, III-6, III-7, IV-2, IV-3 & IV-4 does not have widow's peak. So their genotype will be ww.

I-1 and I-2 will have genotype Ww each because their daughter II-3 has a genotype ww. So both the parents should have a recessive gene.

II-1 will have genotype Ww as his spouse (II-2) is ww and they have a daughter (III-1) who does not have widow's peak.

II-4 will have genotype Ww as her spouse (II-3) is ww and they have a daughter (III-5) who does not have widow's peak.

III-2, III-3, III-4 have widow's peak and will have genotype Ww as their parents are Ww and ww.

Both parents of IV-1 has a genotype of Ww. so he can have genotype WW or Ww. Hence we cannot say for certain whether IV-1 has WW or Ww.