Here is a pedigree of a family with Charcot-Marie-Tooth (CMT) disease and a gel

Question

Here is a pedigree of a family with Charcot-Marie-Tooth (CMT) disease and a gel with the results of PCR amplification of the S21 microsatellite. S21 is tightly linked to the gene that causes CMT when mutated. 1 2 1 2 -1 -2-1-21-3 Microsatellite S21 Note; bands are of equal intensity A. Considering both the pedigree and the microsatellite data, what is the mode of inheritance for CMT? A. B. C. D. E. Autosomal dominant Autosomal recessive X-linked dominant X-linked recessive More than one of the above is possible

Explanation / Answer

Here the answer is A. Autosomal dominant.

Lets start with the other non possible answers,

In case of autosomal recessive inheritance the mother form generation 1 which is affected must have both the allele which is recessive hence in generation two all the individuals remain carrier or normal because father is absolutely normal. For autosomal recessive condition to become affected, both the parent must be carrier or affected. So this possibility is incorrect.

Lets try another possibility of X link. If it is X link recessive than the mother must carrie both the X which are affected. Even if it is X link dominant the mother must have one allele which is mutated. In either case, it will firstly affects male candidate of offspring. But in offsprings, only one male (II-1) is affected, II-3 is normal, this indicates that the possibility of having X link inheritance of any kind, is not possible in this pedigree. Here the female of generation II is affected which is also favours that the inheritance is not X link because she will be recessive.

From the gel analysis it is confirmed that the inheritance pattern is autosomal dominant. From the analysis we can say that allele B is mutant allele and it is present in both affected case II-1 and II-2 but not present in II-3 which is confirms the autosomal inheritance.

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.