Question

!. Why does it make sense that tRNA and rRNA molecules are more stable than mRNA molecules?

2. What is meant by the genetic code being universal and redundant?

Answer 1

1. RNA is generally unstable because of the presence of 2' OH group, which makes the phosphodiester bond unstable eventually making the molecule susceptible to nucleophilic attack and autohydrolysis. The self cleavage reaction occurs when the free OH present in the solution deprotonates 2’OH HOČH, OH 3’and 2’OH group — — OH OH The tRNA, rRNA and mRNA are major types of RNA that plays a significant role in formation of protein from DNA. tRNA molecules serves as adaptor molecules that brings the amino acids to the ribosome for their assembly. The rRNA on the other hand helps in maintaining the structure of ribosome. The mRNA is usually formed from DNA by transcription and it later translates to protein. RNA is usually single stranded where the 2 OH group reaches the phosphorus atom and can cause cleavage of the chain. However when RNA forms a secondary structure or double stranded structure like we see in tRNA and rRNA then the RNA is more stable compared to mRNA. This is due to the limited movement the hydroxy group which makes the phosphorous group inaccessible. This is the reason why the ratio of tRNA and rRNA is more compared to mRNA. 2. The genetic code is universal because all living organisms present on the Earth usually have the same genetic code. The codons that specify the 20 standard amino acids in our cell is same as used by the bacteria, plants, fungi and other species of animals. The genetic code is redundant or degenerate because one amino acid can have multiple codons but a single codon will not code for multiple amino acid. Example The codons UUU and UUC codes for the amino acid phenylalanine, and CUU, CUC, CUA, and CUG codes for Leucine.