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10.2 Inheritance

IB Syllabus Statements

Understandings:

  • Gene loci are said to be linked if on the same chromosome.

  • Unlinked genes segregate independently as a result of meiosis.

  • Variation can be discrete or continuous.

  • The phenotypes of polygenic characteristics tend to show continuous variation.

  • An understanding of inheritance allowed farmers to selectively breed their livestock for specific characteristics.

  • Chi-squared tests are used to determine whether the difference between an observed and expected frequency distribution is statistically significant.

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Applications and skills:

  • Application: Morgan’s discovery of non-Mendelian ratios in Drosophila.

  • Application: Completion and analysis of Punnett squares for dihybrid traits.

  • Application: Polygenic traits such as human height may also be influenced by environmental factors.

  • Skill: Calculation of the predicted genotypic and phenotypic ratio of offspring of dihybrid crosses involving unlinked autosomal genes.

  • Skill: Identification of recombinants in crosses involving two linked genes.

  • Skill: Use of a chi-squared test on data from dihybrid crosses.

Videos

Dihybrid Crosses

Gene Linkage Practice Question

Morgan's Discovery of New Ratios

Gene Linkage

Polygenic Inheritance

Gene Interaction

Environmental Influence on Traits

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Topic 10.2 Inheritance HookED SOLO Hexagons

Topic 10.2 Inheritance SSaQ (Syllabus Statement as Questions)

  • Explain what it means when gene loci are said to be linked.

  • Which types of genes segregate independently as a result of meiosis? Linked genes or unlinked genes? Explain.

  • Explain the difference between discrete and continuous variation.

  • Explain why phenotypes of polygenetic inheritance tend to show continuous variation.

  • Explain how chi-squared tests can be used in genetics.

  • Outline Morgan’s discovery of non-Mendelian ratios in Drosophila.

  • Outline how Punnett squares can be used to analyze dihybrid crosses.

  • Discuss how environmental factors can also influence polygenetic traits such as height.

  • Explain how you would express a ratio from the results of a dihybrid cross.

  • Outline how you would identify recombinants in crosses involving two linked genes.

  • Why does the law of independent assortment not apply for linked genes?

  • When showing dihybrid crosses, how do you use notation to show that the genes are linked?

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