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BIOL 210 Problem Set 3

Week 3, Sep 16-20

ps3.Rmd

General Instructions for Problem Sets

The goal of the problem sets is to give you practice thinking about and working with the concepts that we are covering. You may work with others to complete these assignments but should submit your own responses (not copied from someone else’s response).

Before completing a problem set, you should review the content videos for the week and it may be helpful to complete those before the related class periods as well.

Once you have answered the questions and before you turn in your responses, check your work against the answer key (linked for each problem set). If your responses are missing important information or incorrect, you need to correct them, using a different color font and explaining why your original answer was insufficient.

Use the link at the top of this page to turn in your completed assignment, including corrections.

About Information Transmission (Mitosis and Meiosis)

  • Background reading from the open textbook Biology 2e at Openstax – you can read online or download a PDF.

    • The Cell –> Chapter 10. Cell Reproduction
    • Genetics –> Chapter 11. Meiosis and Sexual Reproduction

  • Schmerler, S and GM Wessel. 2011. Polar bodies—more a lack of understanding than a lack of respect. 78:3-8.

    This is another awesome review paper describing the diverse ways in which organisms produce and use polar bodies in meiosis. While they degenerate in humans (we are SO boring!), they can be a super important part of the development of others – from flowering plants to parasitic wasps.

  • Wilkins, AS, and R Holliday. 2009. The evolution of meiosis from mitosis. Genetics 181:3-12.

    In this article, the authors present a hypothesis for the evolution of meiosis from mitosis, review the available evidence bearing on the hypothesis, and propose possible tests of the hypothesis.

About Life Cycles

  • Background reading from the open textbook Biology 2e at Openstax – you can read online or download a PDF.

    • Biological Diversity –> Life cycle information is available in taxon-specific chapters.

  • From Gathering Moss, The Advantages of Being Small and Back to the Pond

  • Mable, BK, and SP Otto. 1998. The evolution of life cycles with haploid and diploid phases. BioEssays 20:453-462.

    This review paper describes what we know about the evolution of variation in the life cycle. I.e., why are some organisms haploid dominant, others diploid dominant and still others have prominent haploid phases AND prominent diploid phases?

Questions

  1. Consider the processes of cell reproduction.
    1. How is cell division similar and different in prokaryotic and eukaryotice cells?
    2. What do you predict might happen if the spindle fibers did not form during mitosis in a eukaryotic cell?
    3. What do you predict might happen in a prokaryotic cell if a protein important in constricting the plasma membrane and cell wall during cytokinesis was non-functional?


  2. In the fruit fly Drosophila melanogaster, a new zygote is created when sperm fertilize eggs inside the female parent’s oviduct. The sperm and eggs are haploid, the products of meiosis, while the new zygote is diploid. The female parent then lays the fertilized egg (zygote) on a suitable food source. Eggs are white, ovoid, and about 0.5 mm long. About 21 hours after they are laid, eggs hatch and the larvae emerge. The larvae develop in stages known as instars, which are common to many insect species. The newly emerged larvae, known as the first instar, are voracious eaters. They are tiny and difficult to see with the naked eye. The larvae grow rapidly, and within about two days, the first instar will molt into the second instar. These larvae will eat, grow, and molt again to become the third instar. After the third instar crawls out of the food and onto the surface, the larvae begin to pupate. In the pupal stage, the larval body shortens and the cuticle hardens and becomes pigmented, developing into the pupal case. Metamorphosis occurs within the pupal case; dormant localized tissues that originated during the embryonic stages develop into their adult forms, while the remaining larval tissue is broken down to furnish both raw material and the energy needed for adult development. After three days, the adult emerges. The adult flies reach sexual maturity and begin producing new gametes about eight hours after emerging from the pupae, and then the cycle can begin again.

    For each of the following, indicate whether the situation describes cells that are haploid or diploid and whether mitosis or meiosis is occurring:

    • sperm produced in the male fly
    • unfertilized eggs produced in the female fly
    • a new zygote before the egg has hatched
    • 1st instar larvae growing rapidly
    • 3rd instar larvae growing rapidly
    • a pupa develops into an adult
    • the body cells of an adult fly


  3. On meiosis.
    1. What are three ways in which meiosis differs from mitosis?
    2. What two processes during meiosis result in genetically unique daughter cells? Explain how they create genetically variable daughter cells.

  4. Among the related readings are a couple of chapters from Gathering Moss (The Advantages of Being Small and Back to the Pond). In Back to the Pond, Kimmerer talks about the moss life cycle, which is different from that of vascular plants. Check out the graphic of a moss life cycle from Biology 2e (link). Note that mosses belong to a group called the bryophytes. Then examine the image below.

    What can you tell me about the parts of the moss life cycle that are visible to you in this image? How do moss life cycles differ from those of vascular plants such as angiosperms and gymnosperms?

    5. Image of a single chromatid

  5. Weekly Reflection. Consider this week’s material and reply to one or more of the following prompts:
    • What was confusing or interesting to you about this week’s material?
    • Did you have any key insights while studying this material?
    • Does anything from this week’s material particularly stick with you?


When you are finished, check your responses on the key for PS3.

Remember to sign the Honor Code on your assignment.