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#1
06-09-2010
 USMLE Forums Scout Steps History: Not yet Posts: 17 Threads: 5 Thanked 0 Times in 0 Posts Reputation: 10
Genetic Pedigree Question

Given this pedigree,

click to enlarge

what would be expected of the III generation?

a) The probable pattern of inheritance shown by the disease in this family is autosomal recessive.
b) If recombination does not occur the probability that III 1 will be affected if she has an AB marker genotype is 1.
c) If recombination does not occur, the probability that III 1 will be affected if she has a BB marker genotype is 1.
d) If the recombination fraction between the disease and marker loci equals 0.04, the probability that III 1 will be affected if she inherits an AB marker genotype equals 0.96.

#2
06-10-2010
 USMLE Forums Scout Steps History: Not yet Posts: 51 Threads: 2 Thanked 32 Times in 14 Posts Reputation: 42

I think its C

Last edited by inder; 06-10-2010 at 07:36 AM. Reason: accidently put B instead of C
#3
05-28-2011
 USMLE Forums Guru Steps History: --- Posts: 332 Threads: 48 Thanked 168 Times in 107 Posts

Any more thought on this? what do you think is the correct answer?
#4
05-28-2011
 USMLE Forums Addict Steps History: CS Only Posts: 109 Threads: 23 Thanked 23 Times in 19 Posts Reputation: 33
D

Quote:
 Originally Posted by usluipek Any more thought on this? what do you think is the correct answer?
its D i guess.. a probability of 1 means the child is definitely affected..
#5
05-28-2011
 USMLE Forums Addict Steps History: 1 + CS Posts: 113 Threads: 8 Thanked 88 Times in 61 Posts Reputation: 98

Quote:
 Originally Posted by lynk Given this pedigree, Attachment 824 click to enlarge what would be expected of the III generation? a) The probable pattern of inheritance shown by the disease in this family is autosomal recessive. b) If recombination does not occur the probability that III 1 will be affected if she has an AB marker genotype is 1. c) If recombination does not occur, the probability that III 1 will be affected if she has a BB marker genotype is 1. d) If the recombination fraction between the disease and marker loci equals 0.04, the probability that III 1 will be affected if she inherits an AB marker genotype equals 0.96.
why not B)?
#6
05-28-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,357 Threads: 194 Thanked 3,259 Times in 881 Posts Reputation: 3269

Quote:
 Originally Posted by lynk Given this pedigree, Attachment 824 click to enlarge what would be expected of the III generation? a) The probable pattern of inheritance shown by the disease in this family is autosomal recessive. b) If recombination does not occur the probability that III 1 will be affected if she has an AB marker genotype is 1. c) If recombination does not occur, the probability that III 1 will be affected if she has a BB marker genotype is 1. d) If the recombination fraction between the disease and marker loci equals 0.04, the probability that III 1 will be affected if she inherits an AB marker genotype equals 0.96.
#7
05-28-2011
 USMLE Forums Guru Steps History: Not yet Posts: 324 Threads: 70 Thanked 236 Times in 143 Posts Reputation: 246

can anyone elaborate it in a detail?
#8
05-28-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,357 Threads: 194 Thanked 3,259 Times in 881 Posts Reputation: 3269

Quote:
 Originally Posted by struggle can anyone elaborate it in a detail?
I know that A) & D) are incorrect...but I´m not sure if the right answer is C) or B)...I chose C, but I was guessing
#9
05-28-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,357 Threads: 194 Thanked 3,259 Times in 881 Posts Reputation: 3269

Lynk, could you tell us what is the right answer? :sorry:
#10
05-28-2011
 USMLE Forums Scout Steps History: 1+CK+CS Posts: 88 Threads: 25 Thanked 17 Times in 10 Posts Reputation: 27

i think its B....
#11
05-30-2011
 USMLE Forums Addict Steps History: 1 + CS Posts: 113 Threads: 8 Thanked 88 Times in 61 Posts Reputation: 98

I found the answer, but I don't understand why....HELP:sorry::sorry:

c) If recombination does not occur, the probability that III 1 will be affected if she has a BB marker genotype is 1.

Feedback:

The pedigree points to autosomal dominant inheritance with two generation involvement and male to male transmission. II 2 has inherited both the disease and allele B from his father. Therefore if III 1 inherits allele A from her father the probability that she will be affected equals 0 if there is no recombination, or 0.04 if the recombination fraction = 0.04.

 Tags Genetics-, Step-1-Questions

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