Causality1 Learning Goal Interpret Causality Fibroblasts are

Causality1

Learning Goal:

Interpret Causality

Fibroblasts are cells that can be isolated from the connective tissue under the skin and grown in culture. Normally these cells retain the properties of fibroblasts as they divide for many generations in culture, but if we do an experiment in which the fibroblasts are forced to take up a highly expressed copy of the MyoD gene, they rapidly differentiate to become muscle cells.

a) MyoD expression is sufficient to cause fibroblasts to differentiate to muscle cells in culture

b) MyoD expression is correlated with muscle cell differentiation in culture

c) MyoD expression is necessary and sufficient to cause fibroblasts to differentiate to muscle cells in culture

d) MyoD expression is necessary for fibroblasts to differentiate to muscle cells in culture

Solution

Answer: d) MyoD expression is necessary for fibroblasts to differentiate to muscle cells in culture

Explanation:

We can NOT say that MyoD expression is sufficient to cause fibroblasts to differentiate to muscle cells in culture, as other factors could have helped to make fibroblast prone to become muscle cells, and the increasing expression of MyoD was the last triggering event needed. For example, culturing the fibroblasts in petri dishes probably changed their genetics making them prone to become muscles cells if MyoD expression increased. First scientists will need to check the difference between a fibroblast in humans and in culture (find mutations), determine which genes could have changed and see if any of those mutations are also needed, and work together with MyoD to cause fibroblasts to become muscle cells in culture. Therefore, the options a and c can\'t be the answer.

In this experiment, we observe a correlation between the high expression of MyoD and the rapid differentiation to become muscle cells. Correlation is when there is observed covariation, in this case, fibroblasts variated becoming muscles cells when MyoD expression levels variated to be higher, so there is covariation. Correlation is necessary but not a sufficient condition for causality.

A necessary cause is the one that precedes the effect, in this case, MyoD expression precedes the differentiation of fibroblasts to muscle cells in culture. So yes the statement MyoD expression is necessary for fibroblasts to differentiate to muscle cells in culture is the right answer.

Option B, MyoD expression is correlated with muscle cell differentiation in culture, is also correct by what is wrote in paragraph 2 of the explanation, but option D, is the right answer even more, as it necessary is when the cause precedes the effect, and it is true that MyoD expression preceded the effect.

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