1. Both miRNA and siRNA in eukaryotes and riboswitches in bacteria are capable o

Question

1. Both miRNA and siRNA in eukaryotes and riboswitches in bacteria are capable of regulating gene expression. Explain two specific differences in the mechanisms of miRNA/siRNA gene regulation in eukaryotes and riboswitches in bacteria?

2. We are examining nucleotide substitutions in a histone protein gene and in a growth hormone gene in several species of rodents. We observe that the ratio of nonsynonymous to synonymous nucleotide substitutions (Ka/Ks) is 0.1 for the histone protein gene, but is 1.5 for the growth hormone gene. For each gene, what does this ratio tell us about evolution of these genes with regard to selection and neutrality? Give a brief explanation for each answer.

Explanation / Answer

miRNA/siRNA bind to specific mRNA and increase or decrease its activity. It is initiated by the enzyme called as Dicer, which cleaves dsRNA molecules into short RNA molecules.

Riboswitch is a regulatory segment of mRNA itself that can bind a small molecule which modulates the production of protein by mRNA. The mRNA contains the riboswitch is directly involved in regulating its activity.

The Ka/Ks ratio is used to infer the direction and magnitude of natural selection acting on protein-coding genes.

A ratio greater than one implies positive or Darwinian selection;

less than one implies purifying (stabilizing) selection;

and a ratio of one indicates neutral (i.e. no) selection.

The histone gene implies purifying selection, whereas hormone gene shows Darwinian selection

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

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