Biological Science: Genes, Development, and Evolution

Chapter Information

  • Title: Biological Science

  • Edition: Eighth Edition

  • Authors: Pearson, Freeman, Quillin, Allison, Black, Podgorski, Taylor, Carmichael

  • Referenced Chapters: 21 Part II and Sections 47.4

  • Focus Topics: Genes, Development, and Evolution: This section specifically delves into the intricate mechanisms of genetic regulation, the sequential stages of embryonic development, and the overarching principles of how changes in these processes contribute to evolutionary adaptations across species.

Important Announcements

  • Lab Practical Review:

    • Date: This is the last opportunity for a hands-on review session before the actual lab practical examination. Students are strongly encouraged to attend.

    • Details: Review items, specimens, and experimental setups are available in the lab during designated open lab hours. Students are highly encouraged to practice critical hands-on skills essential for the practical, such as:

      • Pipetting: Mastering accurate volume measurement and transfer, a fundamental skill in molecular biology.

      • Sexing flies: Identifying the gender of Drosophila melanogaster, crucial for genetic crosses and developmental studies.

      • Other laboratory techniques: Including microscopy, preparing slides, and general lab safety protocols.

    • Note: Please be aware that no further open lab sessions will be available after the Thanksgiving break, making attendance prior to this date imperative for preparation.

  • Peer Tutoring Availability:

    • Final sessions: These are the last scheduled peer tutoring sessions for the semester, offering valuable one-on-one or small-group assistance with course material.

      • Tuesday, 2nd: 8-10 PM at Science Center (Library) with Katelyn May. Focus often includes problem-solving and conceptual clarification.

      • Thursday, 4th: 4-6 PM at Science Center (Library) with Giovanna Kalin. These sessions can be particularly helpful for reviewing complex topics.

      • Sunday, 7th: 12-2 PM at Science Center (Library) with Matt Shattuck. Ideal for last-minute questions and comprehensive review before exams.

  • Office Hours:

    • Dr. Church: Thursday, 4th from 12 PM-2 PM in Science Center. Students can discuss course content, research interests, or academic concerns directly with the instructor.

    • Dr. Phelan: Thursday, 4th from 10 AM-12 PM in Science Center. An excellent opportunity for in-depth questions and personalized guidance.

    • Additional appointments: Instructors are often available for individual meetings outside of regular office hours, arranged as per mutual convenience and availability, to accommodate student needs.

  • Group Study Hours for Biology:

    • Post Exam 4 sessions: These sessions are specifically scheduled to support students in consolidating their understanding after the fourth major exam, fostering collaborative learning.

      • Saturday, 6th: 2-4 PM in Science Center. A good time for collective review and discussion of challenging topics.

      • Monday, 1st and 8th: 8 PM-10 PM in Science Center. These evening sessions are designed to provide a structured environment for group work and peer learning.

Genetic Regulatory Cascade in Fruit Fly Embryos

Overview of Developmental Genes

The development of a complex organism like the fruit fly (Drosophila melanogaster) from a single fertilized egg is orchestrated by a precise sequence of gene activities, forming a genetic regulatory cascade. This cascade ensures the correct formation of body segments and specification of cell identities.

  • Maternal Effect Genes: These genes are transcribed by the mother during oogenesis, and their messenger RNA (mRNA) or protein products are deposited in the egg cytoplasm before fertilization. They encode morphogens, signaling molecules that establish concentration gradients along the anterior-posterior and dorsal-ventral axes of the early embryo (e.g., Bicoid, which is concentrated at the anterior pole and is crucial for head and thorax development, and Nanos for the posterior end). These gradients provide positional information that instructs subsequent gene expression.

  • Gap Genes: Activated by the maternal effect genes, gap genes (e.g., hunchback, Krüppel, giant) are among the first genes transcribed in the embryo's own nucleus. They control the formation of large, contiguous body regions or segments along the anterior-posterior axis. Mutations in gap genes lead to