Questions

Testing Yourself

Below is the answers to the thick stack of mcqs given before common test 2. This section is only applicable to those who have yet to tackle those answers. There are mistakes (3-4) or check in with me for clarification.



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Lethal Genes

This is a follow-up from a discussion that veered from mcq discussion. when do we consider a gene as lethal? how lethal is lethal? when does the victim die?

Most of the examples we came across for lethal genes are usually taken when zygotes are unable to form properly leading to death at birth, stillborn or sometimes death as an infant.

But a further enquiry showed that the definition is wider to include 'as long as the gene lead to death'. Thus, it is regardless of age although the main contributing factor must be the gene.

Nevertheless, any question pertaining to lethal genes will be stated.
Thus to clarify, under Mendelian G Qn 22 + 23, both are talking about lethal genes and in the case of 23, because homozygous victim will die in children, M & C could have been homozygous.

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REsponses

After a heated discussion, it is my pleasure to round things up before we come to blows with one another. =)

1. Firstly I would talk about physiological concept on what is a stimulus. We identify a stimulus because there has been a change in the overall physiological condition of an individual. Thus we identify increase in bld sugar as a stimulus, only because there was a basal level to work with. such an increase would upset the balance and has to be regulated. And a decrease in bld sugar is also a stimulus. Stimulus does not have to excite only.



2. 'Responses' in question 30. Everyone has different takes on it and why is that so? because some tried to fit it into the receptor/stimulus-controlcenter-effector/response system. And they choose decrease in blood sugar as a response. But I would like to remind you that a decrease in blood sugar, is actually not a response under the system. The response would have been increase conversion of glucose to glycogen, increase in metabolic rate, increased gluconeogenesis. The RESULT of the responses is decreased blood glucose level which still serve as a stimulus to the receptors in the pancreas

Here it would be more appropriate to talk about general bodily responses as ZH had tried to explain. When we eat, the first response detected within the body (in the blood) would be a rise in bld sugar, then etc.
As to B's retort on running, there are too many factors I had running thru my mind because, the heart, muscles and lungs are involved but I guess there would be a drop in bld glucose level first for utilisation of muscles before the carbonate level in bld increase blah blah... and that drop would be the stimulus as well (for the pancreas) so the question was irrelevant.

If you have accepted the drop in bld glucose level as the response, you are already accepting it as a general bodily response and not anything under the system.


Let's us not forget the order in alphabets but also realise that we are governed by chaos and there is also order in chaos. (physics) =)

Happy wkend =)