A family has a history of Microphthalmia due to inheritance of a specific recess

Question

A family has a history of Microphthalmia due to inheritance of a specific recessive mutant allele of SOX2 with an insertion of 300 bases in the first intron sequence of the SOX2 gene. A genetic counselor and physician are screening the family to determine their genotypes. Indicate whether the following statements are TRUE or FALSE for individuals in the family who arecarriers of the mutant SOX2 allele described:

a) Carries would have a SOX2 protein of normal length and a SOX2 protein that is 100 amino acids longer.

b) Right after transcription but prior to RNA processing, those individuals would have a SOX2 mRNA that is normal length and a SOX2 mRNA that is 300 bp longer.

False

c) Those individuals would have two different lengths of the SOX2 DNA sequence, one normal sequence and one that is 300 bp longer.

Explanation / Answer

(A) False... because the insertion is in intron sequence which will get spliced before translation, so carrier will have a normal length of protein

(B) True... because, carrier SOX2 DNA transcribe 300 bp long m-RNA but after RNA processing, that sequence is being spliced out so have normal length of mature m-RNA

(C) True , Because the inheritance is recessive, Carrier will have only a single copy of mutant allel. So they have one DNA sequence of normal length and other with 300bp long.

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