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(2pts) In humans , mutations in the EDA2 gene display X-linked recessive inherit

ID: 209534 • Letter: #

Question

(2pts) In humans, mutations in the EDA2 gene display X-linked recessive inheritance. The EDA2 gene is required for the formation of sweat glands in the skin. The EDA2gene has enhancers that are required for gene expression in specific regions of the body. enh1 is required for expression in the face; enh2 is required for expression in the torso; enh3 is required for expression in the back. For an individual with the genotype listed below, what phenotype would you expect? (+= wiltype, - = non functional, assume wildtype promoter sequences)

enh1+ enh2- enh3- EDA2+

enh1+ enh2+ enh3- EDA2+

no sweat glands

sweat glands in the face, torso, and back

sweat glands in the face, no sweat glands in the torso or back

sweat glands in the face, a mosaic for sweat glands in the torso, no sweat glands in the back

sweat glands in the face and torso, mosaic for sweat glands in the back

no sweat glands

Explanation / Answer

Answer: Option D is correct.

Explanation:

Enhancers and silencers are cis-regulatory elements. Hence, they can not be complemented.

Given genotype:

enh1+ enh2- enh3- EDA2+

enh1+ enh2+ enh3- EDA2+

enh1+ causes expression in the face.

enh2+ causes expression in the torso.

The given genotype does not have enh3+ enhancer on either chromosome. So, EDA2 is not expressed in the back (Mosaic pattern may be observed).