Back to course 'BIO101: Introduction to Molecular and Cellular Biology (2022.A.01)'

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  • Unit 9: Mendelian Genetics and Chromosomes

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    Do you ever wonder why you look like your brother or sister or where you got your freckles from? Are you concerned about developing a disease another family member struggles with? These are the types of questions that we can answer with an understanding of genetics. In this unit, we learn about the basic principles of inheritance and how likely it is to pass on certain traits from one generation to another.

    Completing this unit should take you approximately 5 hours.

    • Upon successful completion of this unit, you will be able to:

      • explain how information flows from genotype to phenotype at the molecular level;
      • explain how the terms genotype, phenotype, homozygous, heterozygous, dominant, recessive, co-dominant, and sex-linkage are used;
      • given a pedigree, infer whether the trait in the diagram is dominant or recessive, and indicate individual genotypes when possible;
      • solve genetic problems involving monohybrid crosses with dominant and recessive traits, codominant traits, and sex-linked traits;
      • solve genetic problems involving dihybrid crosses with dominant and recessive traits, codominant traits, and sex-linked traits; and
      • define mutation and explain how a mutation, such as that in sickle cell, can result in a changed phenotype.

    • 9.1: Introduction to Genetics

      Genetics is the study of heredity and how different characteristics are passed from generation to generation. It is also the study of variation of characteristics that is important for the diversity of life. Scientists have studied the laws of inheritance and the many exceptions that occur. We often say that our genes give us our traits. That's true, but only indirectly.

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        Patterns of Inheritance: Mendel's Experiments Page
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        Mark as done

        Many consider Gregor Mendel to be the father of genetics because his experiments in simple genetics provided a foundation for modern genetics. Read this section to review Mendel's laws. Be sure to spend some time reviewing the figures. Read this brief introduction to genetics to learn about one of the pioneers of the genetic laws of inheritance.

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        Laws of Inheritance Page
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        Mark as done

        Genes are sequences of DNA. These genes serve as instructions for how to make corresponding sequences of RNA. The sequences of RNA, in turn, serve as instructions for how to build proteins. Proteins are the final product of gene expression, and the particular proteins that are built in the cells of an organism are what give that organism its traits. The traits are directly determined by the proteins, but the traits are indirectly determined by the genes because the genes indirectly instruct the cells how to build the proteins. For any given characteristic (like hair color, for example), there might be multiple possible traits (such as black hair and brown hair).

        The particular trait exhibited by an individual for a particular characteristic (like the black hair trait for the hair-color characteristic) is known as that individual's phenotype. The phenotype depends on the proteins produced, which depends on the version of the corresponding gene (DNA) that an individual possesses.

        We use the term "genotype" to refer to that individual's particular DNA sequence for that particular gene. Therefore, genotype indirectly determines phenotype.

        The laws of inheritance can be used to predict traits in offspring. Read this section to review these laws, and take time to review the figures to review the movement of traits to offspring.

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        Extensions of the Laws of Inheritance Page
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        Mark as done

        Read this section to explore the laws of inheritance in more detail. After you read, you should be able to describe the exceptions of Mendelian genetics, define incomplete dominance and codominance, and explain the inheritance of the ABO blood system.

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        Mutations Page
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    • 9.2: Heredity

      Heredity is the study of how characteristics are passed from parent to offspring. Genetic information is physically expressed through the production of proteins. We call this physical expression the phenotype. Scientists study the probability of certain phenotypes being passed to future generations to help demonstrate the laws of heredity.

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        Introduction to Heredity Page
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        Mark as done
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        Pedigrees Page
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        Mark as done

        Watch this brief video on pedigrees, which are how we learn more about genetics in human populations. Pedigrees are useful in populations like these, where we cannot test in a controlled environment.

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        Sex-Linked Traits Page
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        Mark as done

        Watch this video to review the unique inheritance patterns linked to sex-determining chromosomes.

    • Unit 9 Assessment

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        Unit 9 Assessment Quiz
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        Receive a grade

        Take this assessment to see how well you understood this unit.

        • This assessment does not count towards your grade. It is just for practice!
        • You will see the correct answers when you submit your answers. Use this to help you study for the final exam!
        • You can take this assessment as many times as you want, whenever you want.