Question

Identify which Mill's method is best exemplified. Explain why the Mill's method is exemplified. Demonstrate your understanding of the scientific concept and the logical structure by writing for each passage why the particular Mill's method is best exemplified.There may be more than one method in each passage.

1. The Sac locus was recently shown by linkage analysis and genetic rescue to encode T1R3, thus implicating a member of the T1r gene family in sweet taste detection. Indeed, functional expression studies in heterologous cells revealed that T1R3 combines with T1R2 (T1R2+3) to form a sweet taste receptor that responds to all classes of sweet tastants, including natural sugars, artificial sweeteners, d-amino acids and intensely sweet proteins.

2.Humans and mice show some prominent differences in their ability to taste certain artificial sweeteners and intensely sweet proteins — for example, mice cannot taste aspartame or monellin. Notably, introduction of the human T1R2 receptor into mice significantly changes their sweet taste preferences to a human-like response profile, proving that species differences in sweet taste sensitivity and selectivity are a direct reflection of T1R-sequence variation between species.

Answer 1

ANSWERE: When we talk about Mill’s Methods in Experimental Biology

These are causal reasoning approaches to reconstruct and to justify the rules that allow scientists to infer causal relationships from experimental data consisting of five different methods –

1. The Method of Agreement
2. The Method of Difference
3. The Joint Method of Agreement and of Difference
4. The Method of Residues
5. The Method Concomitant Variation

The Method of Agreement

The best way to understand Mill's methods is maybe through an example. Suppose you and your friends went out together for a birthday part, but when you got home all of you experienced stomach aches and feeling sick. How will you determine what caused the illness? Suppose we draw up a table of the food taken by each friend.

Friend / Food taken	Fries	Pizza	Burger	Pastries	Fallen ill?
You	Yes	No	Yes	No	Yes
Friend 1	Yes	Yes	No	No	Yes
Friend 2	Yes	No	No	Yes	Yes
Friend 3	Yes	Yes	Yes	Yes	Yes

According to the method of agreement if in all cases where an effect occurs, there is a single factor common in all those cases then that factor may cause the effect. When we see in this table the only thing that all of you ate was Fries so applying the rule it can be said eating Fries may cause illness.

The Method of Difference

Friend / Food taken	Fries	Pizza	Burger	Pastries	Fallen ill?
You	Yes	Yes	No	Yes	No
Friend 1	Yes	Yes	Yes	Yes	Yes
Friend 2	Yes	Yes	Yes	Yes	Yes
Friend 3	Yes	Yes	Yes	Yes	Yes

In this case you are the only one who did not fall ill, The particular difference between you and the others is that you did not take Burger. So that is why the others fell ill. This is how the method of difference can be applied. This rule says that when you have one situation that leads to an effect, and another which does not leads to that effect, and the only difference that can be seen is the presence of a single factor in the first situation, we can say that this factor is the cause of the effect.

The Joint Method of Agreement and of Difference

It is when both Method of Agreement and of Difference are together applied. When we apply Joint method we can see it was actually Fries which was causing illness.

Friend / Food taken	Fries	Pizza	Burger	Pastries	Fallen ill?
You	Yes	Yes	No	Yes	No
Friend 1	Yes	Yes	Yes	Yes	Yes
Friend 2	Yes	No	No	Yes	Yes
Friend 3	Yes	Yes	Yes	Yes	Yes

The Method of Residues

According to the method of residues, if we have a number of factors believed to be the causes of a number of effects, and we have reason so that we can believe that except one factor all the other factors, are causes for all the effects, leaving one, then we may say that, that one factor is the cause of the rest of the remaining effect.

The Method Concomitant Variation

The method of concomitant variation says that if a number of situations that causes certain effect, we find a particular property of the effect changing with variation in a factor which was found to be common in those situations, and then we can say that factor is the cause of situation.

Thus using the same kind of example, we might find that you felt somewhat sick having eaten one fry, whereas your Friend1 felt rather not well having eaten a few, and your friend 2 became critically ill having eaten ten in a row. Since the change in the number of fries corresponds to change in the severity of the illness.

                                                            In your question

	T1R3	T1R2	Sweet taste receptor
Human	Yes	No	No
	Yes	Yes	Yes
Rat	Yes	No	No
	No	Yes	Yes

With respect of the table we can state that T1R2 is the factor that is causing the effect (Sweet taste receptor). If it is not present effect cannot be caused. So we can say that the Method of Agreement, the Method of Difference, the Joint Method of Agreement and of Difference can exemplify your situation.

Applying the Method of Agreement

	T1R3	T1R2	Sweet taste receptor
Human	Yes	No	No
	Yes	Yes	Yes
Rat	Yes	No	No
	No	Yes	Yes

Applying the Method of Difference

	T1R3	T1R2	Sweet taste receptor
Human	Yes	No	No
	Yes	Yes	Yes
Rat	Yes	No	No
	Yes	Yes	Yes

Applying the Joint Method

	T1R3	T1R2	Sweet taste receptor
Human	Yes	No	No
	Yes	Yes	Yes
Rat	Yes	No	No
	Yes	Yes	Yes

Applying the Method of Residues

This method is not applicable as there is no other factor which is causing the effect

Applying the Method Concomitant Variation

This method is also not applicable because no other situation is creating the particular effect