The science of sperm

Lectures: 1 session / week, 2 hours / session

Recommended prerequisites are:

7.03 Genetics

7.05 General Biochemistry

7.06 Cell Biology

7.08J Biological Chemistry II

Sperm are tiny, haploid cells with a supremely important job: They deliver the paternal genome to the egg, helping create a zygote that develops into a new individual. For a human male, however, only a small fraction of the sperm produced will ever fertilize an egg. Sperm thus experience intense selective pressure: They must compete against each other, navigate a foreign environment in the female reproductive tract, and interact specifically and appropriately with the surface of the egg. These selective pressures can drive extreme changes in morphology and gene function over short evolutionary time scales, resulting in amazing diversity among species.

In this course, we will explore the ways in which these unique evolutionary forces contribute to incredible specializations of sperm form and function, including hook-shaped heads and multiple tails. We will start with an overview of sperm development in mammals and discuss how selective forces during this process can lead to human disorders, such as dwarfism and webbing of the hands and feet. Next, we will discuss meiotic cell division in males, when major changes in chromosome structure and gene expression become a source of vulnerability in the developing sperm. We will then examine the molecular evolution of sperm-related proteins (e.g. protamines) and discuss why they might evolve faster than proteins in other cell types.

Finally, we will discuss how sperm cooperate or compete against each other in the race to reach the egg, and how these processes affect sperm shape and testis size in different species. Students will learn from the primary research literature with an emphasis on rigorously interpreting experimental data and critiquing analyses and conclusions. Towards the end of this course, we will prepare and examine sperm specimens from several species to see first-hand how the evolutionary processes we discussed have contributed to their diverse morphologies and unique fertilization strategies.

We will meet for 2 hours each week to discuss papers about sperm biology and evolution. Students are not required to have any previous knowledge of the subject matter. The course will use a discussion-based format, driven by the students with guidance from the instructors. At the end of each class, the instructors will introduce the next week's reading material in a short presentation. Students are expected to complete all readings, attend every class, and participate in all class discussions.

The main goal of this course is for students to learn how to read and critically evaluate the primary scientific literature. The journal-club style of class sessions is designed to facilitate this goal in a fun and engaging way. Class assignments will provide students with experience in writing and presenting scientific results. In addition, students will learn theories and approaches used in evolutionary analysis and reproductive biology. By the end of the course:

This course will be graded pass / fail and a passing grade will depend on attendance, participation in class discussions and completion of the required weekly, midterm, and final assignments.

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