Question

As an inspiring scientist in 1960, you decide that the most important problem facing humankind is cancer. Being very clever, you realize that an important way to understand what goes wrong with cell division in cancer cells is to elucidate the fundamental molecular mechanisms by which normal cells divide. You decide to focus on mitosis, when a mother cell physically separates its duplicated chromosomes. Understanding the molecular mechanism(s) of mitosis is a very large problem [In fact, 60 years later (2020) the field is still hard at work on this important problem], so your research advisor suggests that you start by thinking about a general strategy to understand the fundamental mechanism(s) of mitosis.

As a first step to understanding mitosis, you decide to identify (or inventory) the basic parts involved in mitosis. You decide to conduct a genetic screen to identify the parts. For this screen, briefly describe:

a) Which model system you will use and why

b) What effect or ‘phenotype’ you will look for to identify mutations in mitosis

c) One problem you might encounter in performing this screen and how you might overcome it

Answer 1

a) The model system to study mitosis in cancer cells can be the genetically modified mice. They are appropriate model systems for study of any such mutational effects. This is because the biological,genetic and behaviour characteristics closely resemble humans. They are wasy to breed and thus many of the human diseases and deformities can be induced in the mice for study.

b) To identify the mutation in mitosis, one very distinct phenotype or effect that can be observed is the chromosomal mosaicm and the abnormal number of chromosomes. The mitosis normally leads to form two daughter cells with equal number of chromosomes. Hence in cancer cells, there will be abnormal chromosomes in the cells and the number of daughter cells might be increased. That means, the rate of the mitosis will increase greatly.

c) The problem encountered can be that the mutational studies can be due to many other reasons. That means the mitosis abnormality can be due to many other reasons and not just cancerous reasons. This can be elimiinated by limiting the growth conditions and growing the cells in conditions which will ensure the abnormal growth is due to mitotic deformity.