kslaetitia
Forum Newbie
Topics: 3
Posts: 4
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it's easy nbme, but I really don't know how to solve this type of question. somebody please explain step by step? thanks a million!!
21
A 3 year old boy is suspected of having an x-linked immunodeficiency. To establish the pattern of transmission of this genetic defect, DNA is extracted from the T and B lymphocytes of his parents, his two sisters ages 5 and 7 years, and his 3 month old brother. After restriction enzyme digestion, the digested DNA is subjected to gel electrophoresis and probed with a DNA marker that distinguishes the maternal and paternal x chromosome alleles. The results are shown. Based on this DNA analysis, which of the following statements is correct concerning the inheritance of this genetic deficiency?
a. the brother has inherited the defective gene
b. both parents can transmit the defective gene
c. sister 1 is a carrier
d. sister 2 is a carrier
e. both sisters are carriers
f. neither sister is a carrier
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| robin082006
Forum Hero
Topics: 471
Posts: 5,125
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D
Restriction endonuclease digests abnormal allele. Normal allele is shown as two bands and disease allele is shown as 1 band.
Father's allele is not digested (two bands)--> normal
Mother has 1 normal allele and 1 abnormal allele--->carrier
Sister1: heterozygous normal
Sister 2: carrier
Brother: normal
Patient: disease.
Hope it help.
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| ladybug
Forum Senior
Topics: 20
Posts: 57
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Wow! Thanks for this
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| kslaetitia
Forum Newbie
Topics: 3
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thanks a lot robin!!
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| nadiabarati
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thanks robin. God bless you
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| twesting2173
Forum Senior
Topics: 7
Posts: 65
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eeek! i'm so so so confused by this. can someone offer another explaination? i guess i can see how sister 1 has the four (band?) there....one one b from mom, one b from dad, one t from mom, one t from dad...what i just dont get the rest. why does sister 2 only have one line under the B? i guess i can see why the t for sister 2 looks like that (she got a good t from dad and the screwed up one from mom??).
man, i'm proving my self a fool, i know. thanks everyone.
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| eytanraz
Forum Newbie
Topics: 1
Posts: 68
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[quote=robin082006]D
Restriction endonuclease digests abnormal allele.
Excuse me robin but where does the question say that restriction endonuclease digests abnormal allele?!?!
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