Biology, 03.03.2020 06:09 ashleyrover11

Why do RNA viruses appear to have higher rates of mutation?
A) RNA nucleotides are more unstable than DNA nucleotides.
B) Replication of their genomes does not involve the proofreading steps of DNA replication.
C) RNA viruses replicate faster.
D) RNA viruses can incorporate a variety of nonstandard bases.
E) RNA viruses are more sensitive to mutagens.

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Answer from: chanahvanya

B) Replication of their genomes does not involve the proofreading steps of DNA replication.

Explanation:

RNA viruses have upto 1 billion time higher mutation rate than their host. As RNA is more fragile than DNA so these mutations are associated with the adaptability of RNA viruses in changing environment as well with their virulence. The higher mutation rates in RNA are the consequences of following factors.

The DNA of eukaryotes as well as of some viruses have the proofreading mechanism to repair mutations. Even some very high RNA viruses also poses this ability. But most of the viral RNA polymerases lack the ability of proofreading i. e. it cannot rectify the replication errors in RNA. It causes the higher mutation rate in viral RNA.Another comparatively small cause is the presence of uracil base in RNA instead of thymine. Sometime cytosine base changes to uracil and this is detected in DNA because DNA don't contain uracil while it cannot be detected in RNA because it already contains uracil.

Answer from: j015

B) Replication of their genomes does not involve the proofreading steps of DNA replication.

Explanation:j

1. This is because RNA polymerase do not proofread proteins or polymerase components to check for errors and repair.

2.Because RNA viruses usually encoded their replication machinery, therefore they have the ability to replication at high rate which increases chances for mutation, to any length and extent to suits their needs.

Therefore,since there is no check for the number of replication they can go through and no need for correction of replication errors, they have rapid chances for mutation and therefore virulence. Different offspring, with distinct genetic composition from wrong bases insertion and translation and therefore of virulence totally different from the parents will be produced. Thus mutagensis, and virulence continues to increase.

Answer from: Quest

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products

Answer from: Quest

Proteins are the workhorses of the cell, controlling virtually every reaction within as well as providing structure and serving as signals to other cells. proteins are long chains of amino acids , and the exact sequence of the amino acids determines the final structure and function of the protein. instructions for that sequence are encoded in genes . to make a particular protein, a messenger ribonucleic acid (mrna) copy is made from the gene (in the process called transcription ), and the mrna is transported to the ribosome . protein synthesis, also called translation , begins when the two ribosomal subunits link onto the mrna. this step, called initiation, is followed by elongation, in which successive amino acids are added to the growing chain, brought in by transfer rnas (trnas). in this step, the ribosome reads the nucleotides of mrna three by three, in units called codons , and matches each to three nucleotides on the trna, called the anticodon. finally, during termination, the ribosome unbinds from the mrna, and the amino acid chain goes on to be processed and folded to make the final, functional protein

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Why do RNA viruses appear to have higher rates of mutation?
A) RNA nucleotides are more unstab...