Human Genetics 25

Exam Information

  • Exam Date: Friday

  • Exam Topics: Sections six, seven, and thirteen

  • Accommodation: Students planning to take the exam at disability services for extra time should confirm their arrangements.

  • Discussion Assignment:
      - Assignment distribution will occur today.
      - Due time: 11:59 PM tonight.

  • Quiz:
      - Available anytime today until 11:59 PM tonight.

Case Study Overview

  • Topic: Reciprocal Translocation between Chromosomes 9 and 22
      - Results in the formation of a fusion protein that induces Chronic Myelogenous Leukemia (CML).
      - Medications developed in the early 2000s aimed at inhibiting this abnormal protein to induce cancer remission.

  • Discovery: The translocated chromosome was first identified in Philadelphia, leading to the name Philadelphia chromosome.

  • Historical Context: The discovery followed the atomic bombings in Japan, which led to increased cancer cases, particularly CML due to chromosome abnormalities.

Understanding Leukemia

  • Definition of Leukemia: A type of cancer primarily affecting blood and bone marrow.
      - Involves the differentiation of bone marrow stem cells into white and red blood cells.

  • Myelogenous Leukemia:
      - Results in abnormally high white blood cell counts at the expense of other cell types.

Personal Anecdote

  • Mention of a friend's (Patrick's) experience with CML that began during medical school:
      - Symptoms included pain on the left side and an enlarged spleen.
      - Diagnostic Method: Blood draws can reveal leukemia through abnormal cell percentages.
      - Diagnosis confirmed as CML after tests for translocation using FISH (Fluorescence In Situ Hybridization).
      - Treatment: Use of Gleevec (Imatinib), which inhibits the fusion protein and puts patients into remission.
      - Personal health insurance challenges: Gleevec costs about $5,000 per month.

Alternative Treatment Methods for Leukemia

  • Bone Marrow Transplant:
      - A common method to put leukemias into remission.
      - Involves the irradiation of a patient’s bone marrow to eliminate cancerous cells, followed by transplanting healthy bone marrow.

  • CRISPR-Cas9 Technology:
      - Potential method for modifying stem cells directly, though more difficult for certain translocations.
      - Currently, daily medication is often a more feasible approach for patients.

Cancer Treatment Landscape

  • Perspective on curing cancer: Understanding the complexity of cancer treatment and the potential for long-term management strategies.

  • Emphasis on patient monitoring and support rather than expecting a complete cure.

  • Personal accounts and experiences with cancer survival among friends.

Assignment Distribution

  • Discussion assignment includes four or five multiple choice questions.
      - Answers will be revealed after the assignment deadline.
      - Incorrect answers do not lead to penalties; focus is on self-assessment.

Communication

  • Course instructor available for questions via email.
      - Encouragement to reach out with any issues or uncertainties.

Historical Context of DNA as Genetic Material

  • Relayed personal history regarding advancements in genetics and DNA understanding since the 1930s.

  • Description of Griffith's Experiment (1928):
      - Involvement of Streptococcus pneumoniae:
        - Smooth strain (virulent) and Rough strain (non-virulent) used.
      - Phenotype transformation: How dead smooth strain could lead to living rough strain becoming virulent when mixed, indicating genetic material transfer.

Mechanism of Transformation

  • Definition of Transformation: Process where one organism takes up another's DNA, resulting in a phenotypic change.
      - Example: Zebrafish fluorescence via jellyfish gene uptake.

Experiments Demonstrating DNA as Genetic Material

  • Continued from Griffith: Isolation of substances to determine the source of transformation.

  • Use of enzymes (protease, RNase, DNase) to identify DNA as the transforming principle.
      - Results from these experiments showed:
        - Proteins (using protease) and RNA (using RNase) do not transform towards virulence, while DNA (using DNase) does.

  • Confirmation of DNA's role as genetic material despite initial skepticism from the scientific community.

Advances in Understanding DNA Structure

  • Developments from 1944 to 1953 about DNA as the genetic material culminated in Watson and Crick’s modeling of DNA structure.
      - Connection back to historical knowledge about DNA, ribose and deoxyribose sugars, and the fundamental components of nucleotides (sugar, phosphate, base).

Conclusion and Next Steps

  • Structure of DNA discussed, including nucleotide composition.

  • Continuation of DNA and RNA structural discussion in the next class.