RNA and Protein Synthesis
RNA and Protein Synthesis
Introduction: DNA is the molecule that produces all of the traits an organism has. But how do these traits arise? They come from a particular and unique sequence of proteins possessed by an organism. In order to produce the proteins, DNA must first give its instructions to a related molecule called RNA (ribonucleic acid), which then undergoes the process of protein synthesis.
Like DNA, RNA is a nucleic acid comprised of monomers called nucleotides. Each nucleotide has a sugar backbone (in this case ribose) a phosphate group, and nitrogen bases. In RNA, the four nitrogen bases are adenine (A), guanine (G), cytosine (C), and uracil (U). Notice that thymine (T) is missing and has been replaced by uracil. Chargaff's rules still apply here - A goes with U and C goes with G.
Another big difference between DNA and RNA is that RNA is single stranded (see image below).
The process of protein synthesis involves three different types of RNA molecules. The first, mRNA (messenger RNA), is responsible for collecting the message from the DNA in the nucleus and bringing out to the cytoplasm. This process is called transcription. Next, a molecule called tRNA (transfer RNA) starts to assemble free-floating RNA nucleotides and put them into a hairpin shaped structure. Finally, rRNA (ribosomal RNA) attaches to the tRNA (which has the code from the mRNA by this point) and assembles the nucleotides into amino acids. It is these amino acids that bond together to form proteins. This process is called translation.
The sequence of nitrogen bases on the tRNA molecule is used to determine which amino acid is produced. A series of three bases, called a codon, code for each amino acid.
Directions for this Lesson: Answer the practice questions and then watch the video to learn more about how proteins are made.
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