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The molecule limonene has two different enantiomers. One enantiomer smells like lemons, while the other smells like oranges. Why do these two molecules, which are chemically identical except for their three-dimensional arrangement, have such different smells?

A mature mRNA molecule in a eukaryotic cell has a modified guanine cap at one end and a poly-A tail at the other end. What is the primary function of these modifications?

The lac operon in E. coli bacteria contains genes necessary for the metabolism of lactose. When lactose is absent, a repressor protein binds to the operator region of the DNA, preventing RNA polymerase from transcribing the genes. What is the role of this repressor protein?

The genetic code is described as “redundant” or “degenerate” because a single amino acid can be encoded by more than one codon. What is a major advantage of this redundancy?

A polypeptide chain is being synthesized from an mRNA molecule with the sequence 5′AUG−GCA−UAU−3′. Which of the following is the correct sequence of amino acids that would be produced?

A scientist uses a restriction enzyme to cut open a bacterial plasmid and a gene of interest. The ends created are known as “sticky ends.” Why are these sticky ends so important for making a recombinant plasmid?

HIV, the virus that causes AIDS, is a retrovirus. It has an RNA genome. In order to infect a host cell and use the cell’s machinery to replicate, HIV must first convert its RNA into DNA. What is the main reason this conversion is necessary?

In order to respond to a cellular signal, a kinase enzyme attaches a phosphate group to a specific serine residue on another protein, changing its shape and activating it. What is this type of post-translational modification called?

While mRNA vaccines have numerous benefits, they also present unique challenges. Which of the following is a significant challenge associated with the development and storage of the original COVID mRNA vaccines?

The central dogma of molecular biology states that genetic information flows from DNA to RNA to protein. However, certain viruses, such as HIV, can synthesize DNA from an RNA template. What is the name of this process?