There are a number of ways that scientists study protein folding and structure. They include the following processes: mutation studies, x-ray crystallography, and spectroscopy. Mutation studies compare the folding patterns of wild type proteins and those with targeted point mutations. X-ray crystallography is a form of high-resolution microscopy that uses x-rays to study the atomic structure of protein crystals through diffraction patterns. Last, a number of spectroscopy methods are employed to study protein folding by comparing unfolded, folded, and partially folded proteins.

tRNA, or transfer RNA, is responsible for binding amino acids and delivering them to the ribosome during translation. tRNA binds amino acids with its anticodon. The anticodon is a sequence of 3 nucleotides that are complimentary to the codon of a specific amino acid. Anticodons can only bind to codons that are complementary in sequence; this ensures that the correct amino acids are chosen.

Disruption of normal protein folding or denaturation—protein unfolding—occurs under certain environmental conditions. Denaturation is defined as the loss of quaternary, tertiary, and secondary folding through the disruption of protein subunits and bonds. The environmental conditions that cause denaturation include the following: extreme temperatures, chemical interference, and extreme pH levels. Denatured proteins may sometimes refold if conditions stabilize; however, this does not typically happen.

The protein quaternary structure is the highest level of protein architecture and refers to the arrangement of protein subunits and their interactions with one another. There is a range in the complexity in the quaternary structure of proteins from dimers, such as DNA polymerase, to tetramers, such as hemoglobin. These structures are always composed of more than one protein subunit.

The lack of a nuclear membrane in prokaryotes has the advantage of allowing the cell to translate RNA as it is transcribed from DNA. This means that even before the full RNA is produced, the protein coded by that RNA can start being made. Eukaryotes produce RNA inside the nucleus, so it must first be fully transcribed and undergo modifications before it can be moved to the cytoplasm, where translation occurs.

The correct answer is operator. In most operons, repressors bind operators to prevent transcription of downstream genes.

Promoters are sequences of DNA upstream of genes that usually promote transcription by recruiting polymerases and other transcription factors. Enhancers are distant DNA sequences that promote transcription, whereas exons are the coding segments of a gene.

Inactive RNA polymerase must bind to a specific sigma factor in order to become active in gene transcription. Sigma factors are specialized transcription factors involved in recruiting and activating RNA polymerase. Only once RNA polymerase has bound the sigma factor can it identify promoter sequences and initiate transcription.

mRNA is the product of transcription and is not involved in prokaryotic RNA polymerase recruitment. An RNA primer is essential to recruiting DNA polymerase for DNA replication.

RNA polymerase does not interact with the Shine-Delgarno sequence. The Shine-Delgarno sequence is present on some prokaryotic mRNAs and serves as a ribosomal binding site for the initiation of translation. RNA polymerase is only involved in transcription and will bind to DNA, not RNA.

The other answers are all true and unique to prokaryotic transcription. Eukaryotic transcription is much more tightly regulated by transcription factors and DNA packaging (chromatin), and is confined to the nucleus.

The protein quaternary structure is the highest level of protein architecture and refers to the arrangement of protein subunits and their interactions with one another. There is a range in the complexity in the quaternary structure of proteins from dimers, such as DNA polymerase, to tetramers, such as hemoglobin. These structures are always composed of more than one protein subunit.

tRNA, or transfer RNA, is responsible for binding amino acids and delivering them to the ribosome during translation. tRNA binds amino acids with its anticodon. The anticodon is a sequence of 3 nucleotides that are complimentary to the codon of a specific amino acid. Anticodons can only bind to codons that are complementary in sequence; this ensures that the correct amino acids are chosen.