Penetrance (1996 Released)

[DrTacoElf]

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[ctdentist]

Autosomal dominants are expressed 50% in the offspring so genes that have 50% penetrance will be 50% of that 50 so its 25%.

 

[DrTacoElf]

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[lionelhutz]

I too still have problems with this question. Just like DrTacoelf said, what genotypes do we take into account, and if not, why not?

 

[baslug]

i think the trick here is the word 'trait'. it implies that the person is a carrier of a gene... and therefore implies that they are heterozygous (Xx)

A heterozygous individual only has a 50% chance of giving the dominant allele to their offspring - no matter what the genotype of the other parent is. even if the person they mate with is homozygous with the dominant allele (XX), our heterozygous person only has a 50% chance of passing down his dominant allele.

then, of course, you do the rest: at 50% penentrance, you'd expect 25% of the offspring to show the phenotype.

 

[baslug]

here's Kaplan's explanation:

"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 greeen 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."

 

[kaukam]

here's Kaplan's explanation:

"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 greeen 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."

Features of aotosomal dominant di
sease


Ø Trait appears in all the generation
Ø 50% of the offspring of the effected parents will also be effected
Ø unaffected parents do not have effected offspring
not effected by sex .Males and females are equally effected


Now the secondpart of the question is 50% penentrance . So 50% 0f 50% is 25%.

 

[mg777]

What the hell does this have to do w/ being a dentist? Why doesnt the joint commission get practicing dentists to write the nbde I that might apply to the practice of dentistry. Instead they have these people that have never been in private practice or better yet have a phD writing the exam. Can anyone say job security