Question

can anyone help with this? it seems like such a simple question but my brain just isn't grasping it.

in the US approximately one child in every 10,000 is born with phenylketonuria a syndrome that affects individuals homozygous for the recessive allele. given this incidence what percent of the population are heterozygous carriers of the recessive PKU allele? give answer to the nearest hundredth of a percent

Answer 1

The only equations you need for these types of problems:

p + q =1

p = frequency of the dominant allele in the population
q = frequency of the recessive allele in the population

and p^2 + 2pq + q^2 =1

p^2 = percentage of homozygous dominant individuals
q^2 = percentage of homozygous recessive individuals
2pq = percentage of heterozygous individuals

Answer 2

you know it's recessive and they give you a number of individuals, you can convert it to a percentage of homozygous recessive individuals (q^2).

You're trying to find out what 2pq is.

Answer 3

so what is p

Answer 4

p = frequency of the dominant allele in the population

Answer 5

yes I know but I don't know what it is

Answer 6

that's the challenge in the question, if i told you the answer i wouldn't be of much help would i? use the formulas i wrote.

Answer 7

but I don't know how. that's the reason I posted it.

Answer 8

I have a paper with some equations on it so I have that but I don't know what to do with it

Answer 9

they gave you q^2 right?

find q, since p+q=1 -> p=1-q

Answer 10

I have \[p^{2}+2pq+q^{2}=1\] and
p+q=1

Answer 11

look at the last thing i wrote

Answer 12

wouldn't that give a negative number?

Answer 13

how?

taking the squared root of the percentage of homozygous recessive individuals wouldn't give you a negative number.

Answer 14

idk I'm all confused

Answer 15

what are you confused about?

\[q ^{2}= a \to \sqrt{q ^{2}}=\sqrt{a}\]

\[q = \sqrt{a}\]

Answer 16

and how did you come up with that

Answer 17

it's math...

one child in every 10,000 is born with phenylketonuria a syndrome that affects individuals homozygous..

q^2 = percentage of homozygous recessive individuals

so solve for q, just take the squared root of both sides

Answer 18

I'm about to say F it. I don't understand any of this.

Answer 19

so, you have q^2=1/10000

to solve for q, you take the squared root of both sides:

\[q ^{2}=\frac{ 1 }{ 10000 } \to q=\sqrt{\frac{ 1 }{ 10000 }} \to q=0.01\]

so p=1-q = 0.99

2ab is the percentage of heterozygous individuals (i.e. carriers)

2(0.99)(0.01)= 0.0198

1.98 %

Watch this video, i think he explains it well.

http://www.youtube.com/watch?v=xPkOAnK20kw

Answer 20

watched it. still confused.

Answer 21

you have to study genetics and hardy Weinberg theorem

Answer 22

well I know that much.

Answer 23

what don't you understand?

Answer 24

all of it

Answer 25

re-read the question and narrow down what you don't understand, i can't help you otherwise.

Answer 26

I never said you alone had to help me.