A cell interprets the DNA through codons in the mRNA, which are sequences of three nucleotides in a row. These codons determinate an amino acid, the only exception is the stop codon. There are about 64 codons for 20 amino acids and they are universal, which means that a codon for certain amino acid is the same in every organism.

B It describes how RNA is transcribed to amino acids

All living creatures contain genetic information stored in the DNA and RNA molecules. Genes are built in the same way in prokaryotic and eukaryotic cells. Genes are composed of nucleotides, while three nucleotides in a row make a codon. There are about 64 codons for 20 amino acids and they are universal, which means that a codon for certain amino acid is the same in every organism. Therefore, the genetic code is the same for mice and E. coli.

B Both scientists would use the same genetic code because in all organisms the code is read three bases at a time and in the same direction

Eukaryotic cells have three mechanisms that control transcription of genes – transcription factors, cell specialization, and RNA interference. Transcription factors are able to bind on the spot of DNA molecule right before gene starts and attracts RNA polymerase. They can also help in unwrapping chromatin so that certain genes would be exposed. These two mechanisms promote the transcription process. However, transcription factors may also block particular genes.

Cell specialization means that certain genes are expressed in some types of cells and not the others.
RNA interference is a process in which a miRNA bind to its complementary region on the mRNA and damages it, which stops the transcription.

D Transcription factors and gene expression is different in nerve cells and muscle cells