NBDE part I question....help!!

[oasiswhy]

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Hello, everyone!🙂
Here is a question from released paper.

An autosomal dominant trait showing 50 percent penetrance will be phenotypically expressed in what percent of the offspring?
A. 0
B. 25
C. 33
D. 50
E. 75

I am confused.😕 Anyone can help??? Thx!!!!

 

[Basler30]

Penetrance refers to the extent to which a given gene expresses itself. To illustrate, imagine a dominant gene for green hair, G. Both genotypes GG and Gg are expected to phenotypically have green hair. However, due to environmental factors, or due to the effect of other related genes, green hair may not always show phenotypically, even though the individual posseses the dominant G gene. If it actually shows in the appearance of 50% of the individuals who have the appropriate genotype, it is said to have 50% penetrance. The rest of the problem is math. If, for some reason, male parents in a large group express this green trait 50% of the time and female parents also express this green trait 50% of the time, we expect the offspring to express it 50% times 50% or 25% of the time.

So the correct answer to question is choice B.


source : dentalarticles

 

[chorea6]

thank you

 

[oasiswhy]

Penetrance refers to the extent to which a given gene expresses itself. To illustrate, imagine a dominant gene for green hair, G. Both genotypes GG and Gg are expected to phenotypically have green hair. However, due to environmental factors, or due to the effect of other related genes, green hair may not always show phenotypically, even though the individual posseses the dominant G gene. If it actually shows in the appearance of 50% of the individuals who have the appropriate genotype, it is said to have 50% penetrance. The rest of the problem is math. If, for some reason, male parents in a large group express this green trait 50% of the time and female parents also express this green trait 50% of the time, we expect the offspring to express it 50% times 50% or 25% of the time.

So the correct answer to question is choice B.


source : dentalarticles

Thank you!! It really helps a lot!!