Problem 7 Describe the process by which th... [FREE SOLUTION]

Chapter 10: Problem 7

Describe the process by which the information in a eukaryotic gene is transcribed and translated into a protein. Correctly use these words in your description: tRNA, amino acid, start codon, transcription, RNA splicing, exons, introns, mRNA, gene, codon, RNA polymerase, ribosome, translation, anticodon, peptide bond, stop codon.

Short Answer

Expert verified

The gene is transcribed into mRNA, which is spliced and translated by ribosomes into a protein as tRNAs bring amino acids for peptide bonding.

Step by step solution

- Initiating Transcription

Transcription begins in the nucleus when RNA polymerase binds to the promoter region of a gene. This enzyme unzips the DNA and starts synthesizing a complementary strand of mRNA from the DNA template.

- Elongation of mRNA

As RNA polymerase moves along the gene, it continues to elongate the mRNA strand by adding RNA nucleotides. This mRNA strand is a copy of the gene's exons and introns.

- RNA Splicing

After transcription, the initial mRNA strand undergoes RNA splicing where introns (non-coding regions) are removed and exons (coding regions) are joined together to form mature mRNA.

- mRNA Transportation

The mature mRNA exits the nucleus and enters the cytoplasm where it will participate in translation.

- Initiation of Translation

Translation begins with the mRNA binding to a ribosome. This process starts at the start codon (AUG) on the mRNA.

- Correct tRNA Matching

tRNA molecules transport specific amino acids to the ribosome. Each tRNA has an anticodon that complements a codon on the mRNA.

- Amino Acid Chain Formation

The ribosome facilitates the formation of peptide bonds between adjacent amino acids, creating a growing polypeptide chain.

- Elongation of Polypeptide

Translation continues as the ribosome moves along the mRNA, linking amino acids delivered by tRNAs based on each codon's instructions.

- Termination of Translation

When the ribosome encounters a stop codon on the mRNA, translation ends. The completed polypeptide chain is released to fold into a functional protein.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Transcription

Transcription is the first step in protein synthesis. It occurs in the nucleus of a eukaryotic cell. This process begins when RNA polymerase binds to the promoter region of a specific gene. The enzyme then unzips the DNA, exposing the template strand. From this template, RNA polymerase synthesizes a complementary strand of messenger RNA (mRNA). The mRNA strand will include both exons (coding regions) and introns (non-coding regions). Throughout this process, the DNA sequence is effectively transcribed into a complementary mRNA sequence.

RNA Splicing

After the mRNA strand is synthesized, it undergoes a process called RNA splicing. This occurs in the nucleus before the mRNA can exit into the cytoplasm. RNA splicing involves the removal of introns (non-coding regions) from the pre-mRNA. The remaining exons (coding regions) are then joined together to form a continuous coding sequence in the mature mRNA. This spliced mRNA is now ready to be translated into a protein.

Translation

Translation is the next major step in protein synthesis, and it takes place in the cytoplasm. Here, the mature mRNA binds to a ribosome, initiating the translation process. This binding begins at the start codon (AUG) on the mRNA. As the ribosome moves along the mRNA, it reads codons鈥攖hree-nucleotide sequences that specify particular amino acids. For each codon, a corresponding transfer RNA (tRNA) molecule, carrying the appropriate amino acid, pairs with the mRNA through its anticodon. Each successive tRNA adds its amino acid to the growing polypeptide chain, forming peptide bonds between amino acids.

Ribosome

The ribosome is a complex molecular machine that plays a critical role in protein synthesis. Composed of rRNA and proteins, the ribosome reads the mRNA sequence and facilitates the assembly of amino acids into a polypeptide chain. The ribosome has three binding sites: A (aminoacyl), P (peptidyl), and E (exit) sites. The A site is where the tRNA carrying an amino acid first binds. The P site holds the tRNA with the growing polypeptide chain, and the E site is where the empty tRNA exits after it has transferred its amino acid. Through these steps, the ribosome ensures the correct order and linkage of amino acids, forming a functional protein.

tRNA

Transfer RNA (tRNA) is crucial for translating the mRNA code into an amino acid sequence. Each tRNA has an anticodon, a set of three nucleotides that are complementary to a specific mRNA codon. At the opposite end of the tRNA, an amino acid is attached, corresponding to the anticodon. During translation, the tRNA molecules bring amino acids to the ribosome, matching their anticodon with the mRNA codon. This allows each tRNA to deliver the correct amino acid, which is then added to the growing polypeptide chain. Once its amino acid is transferred, the tRNA leaves the ribosome to be reloaded with another amino acid, ready to continue the translation process.

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