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#1




If you don't die after this...you're done with genetics!
Subject I 1 and II 2 have Becker muscular dystrophy (Xlinked recessive inheritance)
Subject III 2 has oculocutaneous albinism (autosomal recessive inheritance, incidence in the general population of 1/10 000. The disease status for both Becker muscular dystrophy and oculocutaneous albinism is unknown for IV 1 and IV 2. click image to enlarge 1) What is the probability that III 3 is a carrier of Becker muscular dystrophy? a) 1/4 b) 2/3 c) 1/2 d) 1 2) What is the probability that III 3 is a carrier of oculocutaneous albinism? a) 1/4 b) 2/3 c) 1/2 d) 1 3) What is the probability that IV 1 is a carrier of oculocutaneous albinism? a) 1/4 b) 1/2 c) 2/3 d) 99/100 4) What is the probability that IV 2 will be affected with Becker muscular dystrophy? a) 1/4 b) 1/2 c) 0 d) 1 5) What is the probability that IV 2 will be affected with oculocutaneous albinism? a) 1/100 b) 1/50 c) 1/24 d) 1/12 Have fun 
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bebix (05312011), DrSick (05312011), Hope2Pass (05312011), INCOGNITO (06042011), Med.Student (05312011), vaibhavmanu (05312011) 
#2




Answer
those questions were some how confusing
these are my answers by the way: 1 a 2 b 3 a 4 a 5 d how many of them are correct & how many wrong?? 
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Claus_CU (05312011) 


#4




My answers
Wow great question.
Here are my answers  1) What is the probability that III 3 is a carrier of Becker muscular dystrophy? a) 1/4 b) 2/3 c) 1/2 d) 1 2) What is the probability that III 3 is a carrier of oculocutaneous albinism? a) 1/4 b) 2/3 c) 1/2 d) 1 3) What is the probability that IV 1 is a carrier of oculocutaneous albinism? a) 1/4 b) 1/2 c) 2/3 d) 99/100 4) What is the probability that IV 2 will be affected with Becker muscular dystrophy? a) 1/4 b) 1/2 c) 0 d) 1 5) What is the probability that IV 2 will be affected with oculocutaneous albinism? a) 1/100 b) 1/50 c) 1/24 d) 1/12 I guessed on the last one! Hope Im right. Im quite weak in genetics though! Looking forward to your answers and explanations. 
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Claus_CU (05312011) 
#5




Not to offend the OP, but this question really sucks cause the pedigree doesn't distinguish if the mother/father/grandfather/grandmother is a carrier or not.. so you're made to assume.
1) C 2) C 3) A 4) C 5) C 
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Claus_CU (05312011) 
#6




haha
Actually, ALL the info is there...this is what you know: "Subject I 1 and II 2 have Becker muscular dystrophy (Xlinked recessive inheritance). Subject III 2 has oculocutaneous albinism (autosomal recessive inheritance), incidence in the general population of 1/10 000. The disease status for both Becker muscular dystrophy and oculocutaneous albinism is unknown for IV 1 and IV 2." the rest is just pure probabilities (if the subject is or not a carrier is indeed a probability) have fun! Last edited by Claus_CU; 05312011 at 11:45 AM. 
#8




correct answer
The correct answer are:
1) What is the probability that III 3 is a carrier of Becker muscular dystrophy? a) 1/4 b) 2/3 c) 1/2 d) 1 2) What is the probability that III 3 is a carrier of oculocutaneous albinism? a) 1/4 b) 2/3 c) 1/2 d) 1 3) What is the probability that IV 1 is a carrier of oculocutaneous albinism? a) 1/4 b) 1/2 c) 2/3 d) 99/100 4) What is the probability that IV 2 will be affected with Becker muscular dystrophy? a) 1/4 b) 1/2 c) 0 d) 1 5) What is the probability that IV 2 will be affected with oculocutaneous albinism? a) 1/100 b) 1/50 c) 1/24 d) 1/12 Thanks everybody! 
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sana akbar (05312011) 
#9




1. D
2. C 3. D 4. B 5. C 
#10




@awaisnaeem86 check the right answers above

#11




BTW:
check this link for the explanations Also you'll find more questions! http://www.oup.com/uk/orc/bin/978019...ces/risk/quiz/ 
#13




i dint understand the Q.NO 23 n 25 ANSWERS.......

#14




Question 23 (aka 3)
Question 23 (aka 3)
probability that IV 1 is a carrier of oculocutaneous albinism? Father aa Mother Aa or AA Probability Mother is a carrier Incidence = 1/10000 = p^2 => p=1/100 HW eq = 2pq = 1/50 Probability Mother not carrier 11/50 Then If mother is a carrier Aa + Father aa aa aa Aa Aa = 1/2 * 1/50 "IV 1 is a carrier" If mother is NOT a carrier AA + Father aa Aa Aa Aa Aa = 1 * 49/50 Then, probability that IV 1 is a carrier of oculocutaneous albinism = 1/100 + 49/50 = 99/100 
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#15




Question 24 (aka 4)
Question 24 (aka 4)
What is the probability that IV 2 will be affected with Becker muscular dystrophy? Xlinked recessive Father X_A Y Mother X_A X_a (her Father has the disease) Posible son if Mother X_A X_a: X_A Y X_a Y Then, probability that IV 2 (male) will be affected with Becker muscular 1/2 
#16




Question 25...I'm still trying to understand the qs...

#17




Wow! Got 3 out 5 .. Not bad!! This was a confidence booster for genetics lol .. but to expect these kinda questions i clearly need wayyy more practice and need to go over everything again!
Thanks for sharing. 
#18




Question 25 (aka 5)
Question 25 (aka 5)
What is the probability that IV 2 will be affected with oculocutaneous albinism? We know from qs. 22 (2) that the probability that III 3 is a carrier of oculocutaneous albinism is 2/3. We also know that II 3 must be a carrier, then the probability that subject II 4 is a carrier is 1/2 (mother & father both carrier OR one of those is carrier and the other is normal) Now we have to calculate the probability that the subject III 4 is also a carrier. Using degree of inbreeding (the degree of risk that both alleles of a pair in a person are descended from the same recent common ancestor) the probability that the subject III 4 is also a carrier is 1/2 * 1/2. If subject III 3 & III 4 are carriers, we'll have: AA Aa Aa aa Finally, putting everything together we have: 2/3 (mom) * 1/4 (dad) * 1/4 (aa) = 1/24 
#19




hi bebix ...
thanks for the reasoning ... good one but i have hard time to understand q 25 line " We also know that II 3 must be a carrier, then the probability that subject II 4 is a carrier is 1/2 (mother & father both carrier OR one of those is carrier and the other is normal)" please explain in detail ... thanks 
#20




Quote:
So II 3 must be Aa Now, her brother (II4) has a 1/2 probability of being a carrier too:  if mom & dad are are carrier (Aa * Aa = AA Aa Aa aa)  if one is carrier and the other is not (AA * Aa = AA Aa AA Aa) 
#22




OMG!!! is this for real?

#23




Thanks a lot ...
Quote:
My genetics professor had fun giving us this to play with a week before midterms... 
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