Genetics Pedigree Worksheet Answer Key Made Easy

Understanding Genetics Pedigree Worksheet: A Step-by-Step Guide

Genetics pedigree worksheets can seem daunting at first, but with a clear understanding of the concepts and symbols used, they can be made easy. In this article, we will break down the basics of genetics pedigree worksheets, explain the symbols and terminology used, and provide a step-by-step guide on how to solve them.

What is a Genetics Pedigree Worksheet?

A genetics pedigree worksheet is a diagram that shows the relationships between individuals in a family and their genetic traits. It is used to study the inheritance of genes and to identify patterns of inheritance.

Symbols and Terminology Used in Genetics Pedigree Worksheets

Before we dive into the step-by-step guide, let’s go over the symbols and terminology used in genetics pedigree worksheets:

• Males: Represented by squares (∎)
• Females: Represented by circles (∘)
• Affected individuals: Shaded or filled-in squares or circles (∎ or ∘)
• Unaffected individuals: Unshaded or empty squares or circles (∎ or ∘)
• Carrier individuals: Half-shaded or half-filled squares or circles (∎ or ∘)
• Marriage: Represented by a horizontal line (-)
• Offspring: Represented by a vertical line (|)
• Genotype: The genetic makeup of an individual, represented by letters (e.g., BB, Bb, or bb)
• Phenotype: The physical appearance of an individual, represented by words (e.g., tall or short)

Step-by-Step Guide to Solving Genetics Pedigree Worksheets

Now that we have covered the symbols and terminology used in genetics pedigree worksheets, let’s go over the step-by-step guide to solving them:

1. Read the question carefully: Read the question and identify what information is given and what is being asked.
2. Draw the pedigree: Draw the pedigree diagram using the symbols and terminology we discussed earlier.
3. Identify the genotype and phenotype of each individual: Use the information given in the question to identify the genotype and phenotype of each individual in the pedigree.
4. Determine the mode of inheritance: Determine the mode of inheritance (e.g., autosomal dominant, autosomal recessive, X-linked dominant, or X-linked recessive) based on the pattern of inheritance in the pedigree.
5. Identify the alleles: Identify the alleles (different forms of a gene) involved in the inheritance pattern.
6. Determine the probability of inheritance: Determine the probability of inheritance of the alleles from one generation to the next.

Example: Autosomal Dominant Inheritance

Let’s use an example of autosomal dominant inheritance to illustrate the step-by-step guide:

Suppose we have a pedigree worksheet with the following information:

The question asks us to determine the probability of inheritance of the dominant allele (B) from the father to his offspring.

Step 1: Read the question carefully

We read the question and identify that we need to determine the probability of inheritance of the dominant allele (B) from the father to his offspring.

Step 2: Draw the pedigree

We draw the pedigree diagram using the symbols and terminology we discussed earlier:

Step 3: Identify the genotype and phenotype of each individual

We identify the genotype and phenotype of each individual in the pedigree:

• Father (∎): Bb, affected
• Mother (∘): bb, unaffected
• Son (∎): Bb, affected
• Daughter (∘): bb, unaffected

Step 4: Determine the mode of inheritance

We determine that the mode of inheritance is autosomal dominant, as the father has the dominant allele (B) and passes it to his offspring.

Step 5: Identify the alleles

We identify the alleles involved in the inheritance pattern:

• B (dominant allele)
• b (recessive allele)

Step 6: Determine the probability of inheritance

We determine the probability of inheritance of the dominant allele (B) from the father to his offspring:

• Probability of father passing B to son: 50% (¹⁄₂)
• Probability of father passing B to daughter: 50% (¹⁄₂)

Therefore, the probability of inheritance of the dominant allele (B) from the father to his offspring is 50%.

💡 Note: The probability of inheritance is calculated based on the genotype of the parents and the mode of inheritance.

Conclusion

Genetics pedigree worksheets can seem daunting at first, but with a clear understanding of the concepts and symbols used, they can be made easy. By following the step-by-step guide outlined in this article, you can solve genetics pedigree worksheets with confidence.