Destroyer bio questions

[DenTony11235]

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I remember reading somewhere that the greatest resistance to blood flow was at arterioles (or was it capillaries??), yet in destroyer it says that as the radius of a blood vessel decreases, velocity and blood pressure increase. Wth?

Also, question 329 states: a certain recessive condition is seen in approximately 1 in every 50 people, but is symptom-free. If a male and female possibly carry the gene, what is the probability that they have a diseased child?

Answer is (.02)(.02)(.25)=.0001

My questions is, why does he use (.02)(.02)? The (.02) stands for homozygous individuals, those that have the condition. Heterozygous mating could also result in the condition no?

 

[biomolecmed]

Looks like Destroyer is correct in the first one. You are right, resistance to flow does increase in capillaries, but it does so because the diameter of the blood vessel decreases. All I am saying is, the smaller the diameter of the blood vessel, the larger the resistance to flow.
I will need to see the exact problem for the second question that you posted.

Hope this helps.

 

[FeralisExtremum]

It appears that with that calculation, it's asking for the chance that any two random people will have an affected child. So the breakdown is:

(Chance of Person 1 having it) * (Chance of Person 2 having it) * (Chance of genes being passed down in a way that the homozygous condition would be expressed)

Mathematically that would be (1/50) * (1/50) * (1/4) or (.02)(.02)(.25).

But...as you point out, the question specifies that these people are carriers, and not affected (otherwise the chance of the gene being passed down would be 1, not .25). Working backward from the answer, I'm assuming the question was trying to say that approximately 1 in every 50 people is heterozygous for the condition, but symptom-free because it is recessive.

As for the first part of your question, blood velocity is inversely proportional to the cross-sectional area. A single artery, for example, is much bigger than a capillary - but there are far more capillaries than arteries, hence it has the total highest cross-sectional area. Capillaries have the highest cross-sectional area, so capillaries have the slowest blood velocity.

You would expect pressure to be inversely proportional to cross-sectional area as well (per Bernoulli's principle) BUT this is not the case in blood vessels. Blood is not an ideal flow and the pumping force of the heart is the major contributor to blood pressure in vessels (hence the drop in pressure as we move away from the heart). The image below should make a lot of this clearer.

It is arterioles (not capillaries) that have the highest resistance to flow.

 

[KyoPhan]

"a certain recessive condition is seen in approximately 1 in every 50 people, but is symptom-free"

Is that how they worded it? It confuses me.

Are they saying that 1/50 people are homozygous recessive for the disease?
Or are they saying that 1/50 people are carriers of the recessive and are symptom free.

 

[DenTony11235]

Did not know all of this and my dat is Thursday! Thanks! And that is it worded exactly. It's a complicated question I state those exactly as they are written to minimize errors.

 

[free99]

Feralis dropping the knowledge. Nice work, brings back memories of physiology.