Problem 4 - Campbell Biology Concepts & Connections

Question

What is the name of the process that produces RNA from a DNA template? What is the name of the process that produces a polypeptide from an RNA template?

Step-by-Step Solution

Answer

Transcription produces RNA from DNA. Translation produces a polypeptide from RNA.

Step 1: Understand the question

Identify the two processes: one that produces RNA from DNA, and one that produces a polypeptide from RNA.

Step 2: Identify process 1: RNA from DNA

The process of creating RNA from a DNA template is called transcription. During transcription, an enzyme called RNA polymerase reads the DNA sequence and synthesizes a complementary RNA strand.

Step 3: Identify process 2: Polypeptide from RNA

The process of creating a polypeptide (a chain of amino acids) from an RNA template is called translation. During translation, ribosomes read the RNA sequence and use it to assemble the correct sequence of amino acids into a polypeptide.

Key Concepts

Transcription

Transcription is the process where RNA is synthesized from a DNA template. It occurs in the nucleus of a cell. During transcription, an enzyme known as RNA polymerase attaches to the DNA at a specific starting point called the promoter. The RNA polymerase moves along the DNA strand, unwinding it and reading the nucleotide sequence. As it reads the DNA, it matches complementary RNA nucleotides to the DNA template, building a single-stranded RNA molecule. This RNA strand is called messenger RNA (mRNA), and it carries the genetic information needed for protein synthesis.

Translation

Translation is the process by which a polypeptide (a chain of amino acids) is synthesized from an mRNA template. This process occurs in the cytoplasm of the cell, specifically on the ribosomes. During translation, the mRNA sequence is read in sets of three nucleotides, known as codons. Each codon corresponds to a specific amino acid. The mRNA is translated into a polypeptide chain as transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome. These amino acids are then linked together in the order specified by the mRNA. Once the entire sequence is read, the newly formed polypeptide folds into its functional shape, becoming a protein.

RNA Polymerase

RNA polymerase is the enzyme responsible for synthesizing RNA from a DNA template during transcription. There are different types of RNA polymerases, but the main one involved in synthesizing mRNA in eukaryotic cells is RNA polymerase II. This enzyme binds to the DNA at the promoter region and unwinds the DNA helix to expose the template strand. It then matches RNA nucleotides to the DNA template, creating a complementary RNA strand. RNA polymerase continues elongating the RNA molecule until it reaches a termination signal, at which point it releases the newly formed RNA strand and detaches from the DNA.

Ribosomes

Ribosomes are the molecular machines that facilitate translation, the process of synthesizing polypeptides from an mRNA template. They are composed of rRNA (ribosomal RNA) and proteins, forming two subunits: a small subunit and a large subunit. The small subunit binds to the mRNA, while the large subunit has three binding sites for tRNA molecules. As the mRNA moves through the ribosome, tRNA molecules bring amino acids to the ribosome in the correct sequence, based on the codons in the mRNA. The ribosome catalyzes the formation of peptide bonds between the amino acids, creating a polypeptide chain. When the ribosome reaches a stop codon on the mRNA, translation ends, and the newly synthesized polypeptide is released to fold into its functional form.