Chapter 13: Problem 6

Explain how complementary base pairing is involved in both transcription and translation.

Short Answer

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Complementary base pairing refers to the specific pairing of nitrogenous bases in nucleic acids, and it plays a crucial role in both transcription and translation. In transcription, it ensures the correct RNA nucleotides are added based on the DNA template strand, with A (DNA) pairing with U (RNA), T (DNA) pairing with A (RNA), G (DNA) pairing with C (RNA), and C (DNA) pairing with G (RNA). In translation, complementary base pairing occurs between anticodons on tRNA molecules and codons on mRNA molecules, ensuring the correct amino acids are added to the growing polypeptide chain.

Step by step solution

Introduction to Complementary Base Pairing

Complementary base pairing refers to the specific pairing of nitrogenous bases in nucleic acids. In DNA, adenine (A) always pairs with thymine (T) and guanine (G) with cytosine (C). In RNA, adenine (A) pairs with uracil (U) instead of thymine. Now, let's break down the processes of transcription and translation and highlight where complementary base pairing plays a crucial role. Transcription:

Initiation

During initiation, the RNA polymerase enzyme binds to the DNA molecule at a specific region called the promoter. This binding unwinds the DNA double helix, exposing the template strand.

Elongation

Elongation involves the synthesis of a new RNA molecule using the DNA template strand. The RNA polymerase reads the DNA sequence and adds complementary RNA nucleotides based on the DNA sequence. Here, complementary base pairing ensures the correct RNA nucleotides are added: A (DNA) pairs with U (RNA), T (DNA) pairs with A (RNA), G (DNA) pairs with C (RNA), and C (DNA) pairs with G (RNA).

Termination

Termination occurs when the RNA polymerase reaches the terminator sequence on the DNA, signaling the transcription process to stop. At this point, the newly synthesized RNA molecule is released from the DNA template. Translation:

Initiation

Translation initiation involves the binding of mRNA to a ribosome. The ribosome recognizes the start codon (AUG) on the mRNA molecule and forms an initiation complex that includes transfer RNA (tRNA) carrying the amino acid methionine.

Elongation

During elongation, each mRNA codon is read by the ribosome, and the appropriate tRNA carrying its corresponding amino acid binds to the mRNA codon through complementary base pairing, called anticodon-codon pairing. Anticodons on the tRNA molecule recognize and bind complementarily to codons on the mRNA molecule, ensuring the correct amino acids are added to the growing polypeptide chain.

Termination

Termination occurs when the ribosome reaches a stop codon (UAA, UAG, or UGA) on the mRNA molecule, signaling the end of translation. The polypeptide chain is released, and the ribosome dissociates from the mRNA. In conclusion, complementary base pairing plays a crucial role in both transcription and translation processes. In transcription, it ensures that the correct RNA nucleotides are added according to the DNA template. In translation, it ensures that the correct amino acids are incorporated into the growing polypeptide chain based on the mRNA codon sequence.

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Explain how complementary base pairing is involved in both transcription and translation.

Short Answer

Step by step solution

Introduction to Complementary Base Pairing

Initiation

Elongation

Termination

Initiation

Elongation

Termination

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