Graduate Studies

Degree Program

Degree of Doctor of Philosophy in Biology

Major Subjects of Specialization/Tracks

A student may pursue major work leading to the doctoral degree in any of the following subjects (tracks): biophysics; cellular biology; developmental biology; genetics; immunology; microbiology; molecular biology and biochemistry, or systems biology. At graduation, a student may choose whether the degree is to be awarded in biology or in the selected major subject. Students who choose to work in the areas of Biological Engineering or Neurobiology may also qualify for a Ph.D. in Biology but are encouraged to enroll in the Bioengineering Option or the Neurobiology option.

Initial Advisory Committee

At the start of the first year of study, incoming students meet with the option representative or faculty member(s) specified by the option representative. The purpose of this meeting is to assist the student in organizing laboratory rotations, and to discuss what additional course work is desirable in light of the student’s past record and research interests.


The major initial responsibility of each student is to explore the various research possibilities available at Caltech before settling into a laboratory for their thesis research. Students are free to rotate in any laboratory at Caltech, not just those in the Division of Biology and Biological Engineering. First-year students should carry out a minimum of two laboratory rotations; three rotations are recommended. It is generally expected that rotations will last a full academic quarter; however, exceptions can be granted with the advance permission of the professor. Choice of laboratory should be made by the end of June of the first year except in extraordinary circumstances. Any exception should be discussed with the option representative.

Formal Classes

During the first year of graduate studies, students are required to take a course on Responsible Conduct of Research (Bi 252) and Research Practice in Biology (Bi 254) [formerly Bi 253, Reading, Writing, Reviewing, Experimental Design and Reproducibility] as well as any two courses of a three-term series, Bi 250abc, that covers the breadth of fields represented in biology at Caltech.

During each year that they are matriculated in the Ph.D. program, students are required to take Bi 251 abc (Biolunch). Students will be required to present their thesis research in Biolunch during their second and fourth years of study.

In addition to these fixed requirements, students must also take courses required by the track they have chosen. This will usually include at least one additional 200-series or upper division 100-series course offered by the Division of Biology and Biological Engineering, and may also include taking three terms of Bi 250 abc.


All students are to serve as teaching assistants for one quarter per year they are in residence, up through the third year.

Admission to Candidacy

The qualifying exam process that a student must complete to be admitted to candidacy is divided into two parts—an oral defense of the proposed thesis research and a written test of competency in the student’s chosen area of research.

The Oral Exam

During winter quarter of the second year, a student is to set up a thesis proposal examining committee and prepare a proposal focused on the research project that they expect to pursue for their thesis research. The proposal is defended by the student in an oral presentation in front of the thesis proposal examining committee by the end of June. (Although it is anticipated that this exam will be completed by June of the second year, it can be delayed until August of the third year if the option representative agrees.) The examining committee comprises four faculty members, with at least three holding full or joint professorial appointments in the Division of Biology and Biological Engineering. One of the members of the committee is appointed as chair. The chair of the thesis examining committee must be a Caltech faculty member other than the student’s adviser. The adviser can, but need not be, a member of the examining committee. The members of the thesis proposal examining committee must certify passage of this exam. In the event that there is inadequate evidence of the capacity to do research, the student may be allowed to petition to re-take the oral exam at a later time.  However, in cases where the committee deems it unlikely that the student will be able to pass a subsequent attempt, the student may be advised to leave the program. In any event, a student cannot remain in the program beyond August of the third year without having successfully completed the requirements for admission to candidacy, except in extraordinary circumstances and with the approval of the option representative and the dean of graduate studies.

The Written Exam

The written qualifying examination is taken in June of the student’s second year in the division. Each student chooses one of the following subjects as a major: cellular and molecular neurobiology; developmental biology; genetics; immunology; molecular biology, biochemistry, and cell biology; or systems neurobiology. The exam chair for that major designs a program of study that culminates in the written exam. M.D./Ph.D. students are not required to take the written test of competency unless their adviser specifies that this is required.

Once a student has successfully completed the oral exam and written exam, he or she can apply to be admitted to candidacy.  According to Institute regulations, this application process must be completed by the end of the third year of graduate study.

Thesis Advisory Committee Meeting

Once a student has been formally admitted to candidacy, he or she picks a thesis advisory committee (TAC). This committee is often the same as the thesis proposal exam committee, but that need not be the case. The thesis adviser must be a member of the TAC. The TAC typically has five members. At least three must be professorial faculty who hold a full or joint appointment in the Division of Biology and Biological Engineering, and at least four must be Institute professorial faculty. 

It is expected that students who have been admitted to candidacy will meet with the TAC once a year for the remainder of their time at Caltech. Students who fail to meet with their TAC in any one year may be deemed to not be maintaining satisfactory progress toward the Ph.D. degree and will be prevented from registering for the subsequent academic year.

Maintaining Satisfactory Progress

It is the policy of the biology option that a graduate student who is making satisfactory progress toward a Ph.D. degree can expect to continue as a registered student with full financial support. To be deemed as making satisfactory progress, a student is expected to fulfill the expectations listed below. In the event that satisfactory progress is not being made, a student can petition to receive the M.S. degree, for which they must have successfully completed one full year of graduate study.

Requirements for satisfactory progress include:

  • Completion of the first-year course requirements during the first year.
  • Joining a laboratory in which a student will perform thesis research before the end of June of the first year in residence.
  • Passing the oral and written parts of the qualifying examination and completing admission to candidacy before the start of the year.
  • Holding a thesis advisory committee meeting in each subsequent year of studies, and having the thesis committee verify that satisfactory progress is being made.
  • Serving as a teaching assistant for one quarter of each academic year spent in residence through third year.
  • Completing Ph.D. studies by the end of the fifth year.

In the event that the student, option representative, and adviser are in agreement, it is possible to make exceptions to the above guidelines and remain in good standing. Extension of thesis work beyond the end of the fifth year requires that the student petition the Dean of Graduate Studies for permission to register for the sixth year. Extensions beyond the sixth year will be allowed only in unusual circumstances.

Once a student has passed admission to candidacy, the responsibility for assessing satisfactory progress lies largely with the student’s thesis advisory committee. If a majority of the committee deems that a student is not making satisfactory progress, the student is at risk of being removed from the program at any time at the discretion of the option representative.

Examination Committee

Requirements for the Ph.D. thesis and examination are determined by a Ph.D. examination committee, which is appointed by the dean of graduate studies for each degree candidate. This committee is usually the same as the thesis advisory committee, but this need not be the case. The option representative must approve the composition of the committee. The committee usually has five members. At least three must be professorial faculty who hold a full or joint appointment in the Division of Biology and Biological Engineering, and at least four must be Institute professorial faculty.

Thesis and Final Examination

The thesis and associated publications are expected to demonstrate that the student has learned how to conceive, plan, and execute experimental and/or theoretical work that reveals new biological information. In addition, it must reveal a deep, broad, and rigorous understanding of the area of research to which the thesis is relevant.  Two weeks after copies of the thesis are provided to the examining committee, chairman, and option representative, the candidate collects the copies and comments for correction. At this time, the date for the final examination is set at the discretion of the major professor and the division chair. The final oral examination covers principally the work of the thesis, and according to Institute regulations must be held at least two weeks before the degree is conferred. Two copies of the thesis are required of the graduate for the Institute library.