Section: Biological and Biochemical Foundations of Living Systems

6) In nerve cells, microtubule-associated proteins (MAPs), most notably MAP2 and MAP tau, act to stabilize microtubules. In a mouse model, a mutant is developed that vastly reduced function across all families of MAPs, leading to increased microtubule degradation. Which cellular activity would likely be most affected?

1. Cardiac muscle contraction
2. Transcription of mRNA from DNA
3. Krebs cycle
4. Meiosis

Microtubules are a component of the cytoskeleton and central to a number of cellular processes that involve movement, such as mitosis and meiosis. They provide the framework for the organization and separation of chromosomes and sister chromatids during that process. Thus (D) is the correct answer. A: The movement created by muscle cells depends on actin and myosin, rather than microtubules. B: Transcription is primarily regulated by enzymes, not microtubules. C: The Krebs cycle depends primarily on mitochondria, not microtubules.