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U7L5 Punnett Squares & Pedigrees

Punnett squares and pedigrees are tools used to predict patterns of heredity and trace traits through generations. A Punnett square uses the alleles from each parent to predict an offspring's possible genotypes. A pedigree traces the occurrence of a trait through a family over multiple generations. Both tools provide probabilities and can help identify inherited disorders. They allow researchers to study genetics and prevent extinction of populations like the European mouflon sheep.

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Unit 7 Lesson 5 Punnett Squares and Pedigrees Copyright © Houghton Mifflin Harcourt Publishing Company
Squared Away Copyright © Houghton Mifflin Harcourt Publishing Company How are Punnett squares used to predict patterns of heredity? • One tool for understanding the patterns of heredity is a diagram called a Punnett square. • A Punnett square is a graphic used to predict the possible genotypes of offspring in a given cross. Unit 7 Lesson 5 Punnett Squares and Pedigrees
How are Punnett squares used to predict patterns of heredity? • Each parent has two alleles for a particular gene. • An offspring receives one allele from each parent. • Each compartment within the Punnett square shows an allele combination in a potential offspring. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 7 Lesson 5 Punnett Squares and Pedigrees
How can a Punnett square be used to make predictions about offspring? • A Punnett square does not tell you what the exact results of a cross will be. • A Punnett square only helps you find the probability that a certain genotype will occur. • Probability is the mathematical chance of a specific outcome in relation to the total number of possible outcomes. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 7 Lesson 5 Punnett Squares and Pedigrees
How can a Punnett square be used to make predictions about offspring? • Probability can be expressed in the form of a ratio, or an expression that compares two quantities. • Probability can also be expressed as a percentage. • A percentage states the number of times a certain outcome might happen out of 100 chances. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 7 Lesson 5 Punnett Squares and Pedigrees
How can a pedigree trace a trait through generations? • A pedigree is another tool used to study patterns of inheritance. • A pedigree traces the occurrence of a trait through generations of a family. • Pedigrees can be useful in tracing sex-linked disorders, or disorders associated with an allele on a sex chromosome. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 7 Lesson 5 Punnett Squares and Pedigrees
How can a pedigree trace a trait through generations? • A woman that is heterozygous for a trait is called a carrier. • She is called a carrier because she can pass the trait to her offspring. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 7 Lesson 5 Punnett Squares and Pedigrees
How can a pedigree trace a trait through generations? • Pedigrees can be useful in tracing inherited disorders such as cystic fibrosis. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 7 Lesson 5 Punnett Squares and Pedigrees
Unit 7 Lesson 5 Punnett Squares and Pedigrees Saving the European Mouflon Copyright © Houghton Mifflin Harcourt Publishing Company • Scientists use genetics to show how the European mouflon sheep can be saved from extinction. • When a population is very small, there is a risk of too much interbreeding, which can cause harmful genetic conditions to appear. • Researchers can identify and breed genetically dissimilar European mouflons in a laboratory. This lowers the risk of inherited disorders.
Unit 7 Lesson 5 Punnett Squares and Pedigrees Saving the European Mouflon Copyright © Houghton Mifflin Harcourt Publishing Company • Scientists use genetics to show how the European mouflon sheep can be saved from extinction. • When a population is very small, there is a risk of too much interbreeding, which can cause harmful genetic conditions to appear. • Researchers can identify and breed genetically dissimilar European mouflons in a laboratory. This lowers the risk of inherited disorders.