I am not sure how to approach those review questions and I am especially stuck on 1,2,3

Question

1. It takes E. coli bacteria 20 minutes to divide. Suppose you were provided with an actively dividing culture of E. coli bacteria grown in media to which radioactive thymine had been added. If you removed a cell from this culture and put it into normal, non-radioactive media and waited 1 hour, how many of its great-granddaughter cells would be radioactive?
2. Chlamydomonas nivalis is a species of algae that thrives in freezing water and snow. Would you expect the genome of C. nivalis to have a higher, lower, or similar G-C content as that of E. coli bacteria?
3. What is an advantage that eukaryotic molecular genetic mechanisms (transcription, RNA processing, translation) have over prokaryotic genetic mechanisms?
4. What is a possible reason why a misfolded protein may accumulate in a cell?

Answer 1

I'm always thinking I shouldn't give the answer, but I'll help guide you to it.

1. We've plated this ecoli in radioactive thymine. We aren't told that there are any other sources of thymine, so if it is dividing, it will be radioactive. 100% of this population is radioactive. Now that population is transferred to a media with normal thymine, and we are looking three generations or cell divisions into the future. So think about how when a cell divides, it will be using this non-radioactive thymine for semiconservative replication, and try to imagine it that way.

2. This is an important question when it comes to understanding animal cell bio, and is fundamental knowledge in understanding cell bio in extreme environments. The key difference is that GC bonds have three bonds whereas AT bonds only have two. As such a high GC content is going to be harder to separate than DNA with high AT content. Think of the impact on how easily these cells are frozen from that perspective.

For both 3 and 4 I want you to write down all the key players that go into each process (eukaryotic vs. Prokaryotic division) and the step by step process of creating a protein. All complications in our understanding of bio and what could go wrong are an issue that could occur at a single step. When creating a properly folded protein, ask yourself what does it take, and what part, if there is a problem, would most easily produce a misfolded protein and often.

I hope this helps.