How does DNA, mRNA and tRNA work?

The following is a DNA strand formed by nucleotides.


3'-TAC CCA CTT CGA ACT- 5'





where


A - Adenine


T - Thymine


C - Cytosine


G - Guanine





1) A modelling kit, while useful in demonstrating the main steps of DNA replication, transcription of genetic information from DNA to mRTA, and translation of genetic information from mRNA to polypeptides, cannot completely mimic the same processes in a living cell. Describe three differences between what actually happens in a living cell and what had been done using the kit.





2) Would a base substitution nearer to the 3' end of the template DNA have a more harmful effect than a base substitution nearer to the 5' end of the template DNA? Explain your answer.

How does DNA, mRNA and tRNA work?
I don't know specifically what kit you're working with, but the major items missing from a kit are likely going to include identifying the histone proteins playing a role in replication. And during transcription of DNA to mRNA, a major omission is likely the promoter regions of DNA that mark an upcoming stretch as a gene, giving poymerase something to bind to. And with translation, the involvement of tRNA is hard to reproduce in a kit.





A base substitution near the 5' end would not necessarily be worse, though a base insertion would be. Knocking the code out of its three step seuqence would change the remaining gene product, since the mRNA and protein get coded for in the 5' to 3' direction. A simple base substitution anywhere may change that one A.A., but the effect is likely going to depend on the new A.A., not the location of it as much.





The basic way it works is DNA gets transcribed into mRNA, which gets translated on the ribosome with the help of specific tRNA molecules into a protein. Since the mRNA's get made as a complimentary molecule to the original DNA sequence, and then the tRNA's technically make another complimentary product, the protein, the DNA then is in the sequence that the protein is made from.
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