Mouse quaking is caused by a recessive dysmyelination mutation ( qk ), which app
ID: 77998 • Letter: M
Question
Mouse quaking is caused by a recessive dysmyelination mutation (qk), which appears to involve defects in alternative splicing of an evolutionarily conserved signal transduction protein. Homozygotes (qk/qk) suffer tremors during exertion. Mature mice may experience seizures and remain motionless for many seconds.
Below is a figure that describes the splicing patterns in various genotypes of quaking and normal mice. Portions of brain MAG (myelin-associated glycoprotein) RNA (including exons 11, 12, and 13) from young (14-day) and adult (2-month) mice are represented. The relative concentration of each RNA is indicated in the gel diagram below. (Figure and data are modified from Wu, J., et al. 2002. Proc. Natl. Acad. Sci. 99: 4233–4238.)
Given this information, select all the true statements.
Given this information, select all the true statements.
Young mice produce two sizes of mRNA. Adult mice produce only one size of mRNA. As both qk/qk and +/qk mice age, the percentage of mRNAs containing exon 12 decreases. Young homozygous qk/qk mice are more likely to produce mRNAs with exon 12 than young heterozygous +/qk mice. Adult mice produce more mRNA than young mice. Adult mice produce the same size and amount of mRNA regardless of whether they are qk/qk or +/qk. 12 A B C D 11, 12, 13 13-AAAAA 11, 13 A +/gk young B qk/qk young C +/ak adult D qk/qk adult Pearson Education, Inc.Explanation / Answer
According to the given data, the A and B represent the young mice and C and D represent the adult mice. A and C lack one allele and thus, encode for low amount of protein. Both the young and adult mice encode for low amount of mRNA, but the adult mice contain samples of same concentrations.
In the above given data it is evident that the adults are unable to express the mRNA with 11 and 13 exons. The young mice are expressing 11 and 13 exons. Thus, young mice are capable of producing two sizes of mRNA and adult mice produce only one size of mRNA.
The 12 exon is not expressed by the adults and therefore, it can be concluded that as mice age, the percentage of mRNAs containing exon 12 decreases.
The Young mice A with genotype (+/qk) do not expresses more amount of mRNA than the young mice B (qk/qk) with exon 12. This results in young homozygous qk/qk mice are more likely to produce mRNAs with exon 12 than young heterozygous +/qk mice.
The young mice B with genotype (qk/qk) produce more mRNA than the two adults.
The adult mice produce the same size and amount of mRNA regardless of their genotype qk/qk or +/qk.
Therefore, statements 1,2,3 and 5 are correct.
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