Mouse quaking is caused by a recessive dysmyelination mutation ( qk ), which app

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.

1) Adult mice produce more mRNA than young mice. 2) Adult mice produce the same size and amount of mRNA regardless of whether they are qk/qk or +/qk. 3) Young homozygous qk/qk mice are more likely to produce mRNAs with exon 12 than young heterozygous +/qk mice. 4) As both qk/qk and +/qk mice age, the percentage of mRNAs containing exon 12 decreases. 5) Young mice produce two sizes of mRNA. Adult mice produce only one size of mRNA.

Explanation / Answer

ANS. The method of mouse quaking is associated with the double knocking as of gene knockout system of mouse. The above mention question is entitled with relevancy of mRNA and RNA. The MAG portion of brain is linked.As, we know that the splicing is the powerful way to regulate the Gene at posttranscriptional level and thus alternative splicing is performed. The qk locus encodes several RNA-binding proteins which shows benefical aspects in the regulation.

The informationn given above W.R.T diagram is that A and B are young mice and B and C are adult mice. Related to the allele A and C lack the one allele thus, it is clear that they encode for low protein level this shows that the level of mRNA is low in both adult and the young mice but, according to the question that adult mice sample possees more concentration as of young mice thus, we can say that the statement first TRUE.with this concept we can further say that adult mice produce same size of mRNA with regardless of qk/qk or +/qk thus these statement is also TRUE.

Here, in the question according to DATA the third statement is FALSE becuase young B produce more mRNA then other two.

Fourth one is TRUE also as 12 exon is not expressed by the adult thus,it should decreases.The last one is also TRUE as in the GEL adult cannot express the mRNA with 11 and 13 exons they are expresssd by the youg ones. Thus ,adult produce one size of mRNA and Young produce two.

further i would like to suggest you that you should read the splicing basics and gene knockout system.Also go through the above research paper to know more abot MAG- i,e, L-MAG ,S-MAG and their role in the process.

Thank you, hope information helps you........good luck

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