--- title: "Predicting Inherited Traits" description: "Explain allele inheritance in sexual reproduction and use one-gene Punnett-square models to predict offspring genotypes and phenotypes under complete dominance, recognizing that many traits have more " canonical: https://lightmysky.com/learn/science/predicting-inherited-traits-mt_o7FJPDsHiW source: https://lightmysky.com/learn/science/predicting-inherited-traits-mt_o7FJPDsHiW.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Predicting Inherited Traits Explain allele inheritance in sexual reproduction and use one-gene Punnett-square models to predict offspring genotypes and phenotypes under complete dominance, recognizing that many traits have more complex inheritance Subject: Science · Area: Ecosystems & Habitats · Ages 13 to 14 Page: https://lightmysky.com/learn/science/predicting-inherited-traits-mt_o7FJPDsHiW ## Ready when they can - Defines allele, dominant and recessive within a two-allele, complete-dominance model - Constructs a Punnett square for a monohybrid cross and calculates probability ratios - Explains the difference between genotype and phenotype - Uses cystic fibrosis as an example of autosomal recessive inheritance and recognizes that human eye color is not fully predicted by a one-gene model ## Lesson: Using inheritance models Genes are sections of DNA carried on chromosomes. Alleles are versions of a gene. For the genes studied here, an individual has two copies, one from each parent. The copies can be the same allele or different alleles. More than two alleles can exist in a population. Many traits, including human eye color, involve several genes rather than this one-gene model. Genotype means the allele combination for a gene; phenotype means the observable trait. In a complete-dominance model, a dominant allele determines the phenotype in a mixed pair. For pea height, T is dominant for tall and t is recessive for short. TT and Tt give tall plants; tt gives short plants. Dominant does not mean better or more common. Other inheritance patterns can work differently. *(drawing: TT and Tt are different genotypes with the same tall phenotype in this model.)* Eggs and sperm carry one allele for the gene. A parent with two different alleles passes either with equal chance in this model. Draw a Punnett square by writing one parent's two alleles across the top and the other's down the side. Keep repeated letters. In each box, join its top allele with its side allele. Write the capital first in a mixed pair. **Example.** For pea seed color, Y is dominant for yellow and y is recessive for green. Cross Yy with Yy: Alleles Y y Y YY Yy y Yy yy Each box combines one allele from each parent. The two Yy boxes are separate pairings. The genotype ratio is 1 YY : 2 Yy : 1 yy. The four pairings have equal chances in this model. Chance = matching boxes / total boxes. In the seed cross, 3/4 predict yellow and 1/4 green, a 3:1 phenotype ratio. Multiply a chance by 100 for a percent, or by a group size for an expected count: 3/4 x 20 = 15. Actual counts can differ. A ratio does not promise a fixed result in every group. Cystic fibrosis follows autosomal recessive inheritance. In this simplified same-variant model, C is a working CFTR allele and c is CF-causing. A Cc carrier does not have the condition but can pass C or c. Two carriers can therefore have a cc child with the condition. Human eye color involves several genes, so this one-gene model cannot fully predict it. **Recap.** Punnett squares combine parental alleles to predict genotype and phenotype chances. Predictions depend on the inheritance model and do not guarantee actual counts. *Lesson, questions and flashcards written for this dataset, with scientific background and question-design study from OpenStax and Khan Academy.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Chromosomes, Genes & DNA](https://lightmysky.com/learn/science/chromosomes-genes-and-dna-mt_6aJUzBYGNs) ## Optional connections - [DNA & Genes](https://lightmysky.com/learn/science/dna-and-genes-mt_0sELh0MYWb) ## Opens up - [Punnett Squares and Monohybrid Ratios](https://lightmysky.com/learn/science/punnett-squares-and-monohybrid-ratios-mt_T4ZC45-77w)