Ch. 10 Molecular Biology of the Gene

Taylor - Campbell Biology: Concepts & Connections 10th Edition

Taylor, Simon, Dickey, Hogan10th EditionCampbell Biology: Concepts & ConnectionsISBN: 9780136538783Not the one you use?Change textbook

Taylor, Simon, Dickey, Hogan 10th Edition

Ch. 10 Molecular Biology of the Gene

Problem 10

Chapter 10, Problem 10

The base sequence of the gene coding for a short polypeptide is CTACGCTAGGCGATTGACT. What would be the base sequence of the mRNA transcribed from this gene? Using the genetic code, give the amino acid sequence of the polypeptide translated from this mRNA. (Hint: What is the start codon?)

Verified step by step guidance

Identify the template strand and the coding strand in the DNA sequence provided. In this case, the given sequence is the coding strand: CTACGCTAGGCGATTGACT.

Transcribe the DNA sequence into mRNA by replacing each DNA base with its complementary RNA base. Remember that adenine (A) pairs with uracil (U) in RNA instead of thymine (T), and cytosine (C) pairs with guanine (G).

Locate the start codon (AUG) in the mRNA sequence. This codon marks the beginning of the translation process and codes for the amino acid methionine.

Translate the mRNA sequence into an amino acid sequence using the genetic code. Each set of three nucleotides (codon) in the mRNA corresponds to one amino acid in the polypeptide.

Continue reading the mRNA sequence codon by codon, translating each until you reach a stop codon (UAA, UAG, or UGA), which does not code for an amino acid but signals the end of translation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Transcription

Transcription is the process by which the genetic information in DNA is copied into messenger RNA (mRNA). During transcription, RNA polymerase reads the DNA template strand and synthesizes a complementary RNA strand, replacing thymine (T) with uracil (U). This process is crucial for gene expression, as it produces the mRNA that carries the genetic code from the nucleus to the ribosome for translation.

Genetic Code

The genetic code is a set of rules that defines how sequences of nucleotides in mRNA are translated into amino acids, the building blocks of proteins. Each group of three nucleotides, known as a codon, corresponds to a specific amino acid or a stop signal during protein synthesis. Understanding the genetic code is essential for determining the amino acid sequence of a polypeptide from the mRNA sequence.

Start Codon

The start codon is a specific sequence of nucleotides in mRNA that signals the beginning of translation. The most common start codon is AUG, which codes for the amino acid methionine. Identifying the start codon is critical for correctly interpreting the mRNA sequence and ensuring that the polypeptide is synthesized from the correct point, leading to the proper amino acid sequence.

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1) Initiation of Translation

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Textbook Question

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.

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Textbook Question

The nucleotide sequence of a DNA codon is GTA. A messenger RNA molecule with a complementary codon is transcribed from the DNA. In the process of protein synthesis, a transfer RNA pairs with the mRNA codon. What is the nucleotide sequence of the tRNA anticodon?

a. CAT

b. CUT

c. GUA

d. CAU

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Textbook Question

A cell containing a single chromosome is placed in a medium containing radioactive phosphate so that any new DNA strands formed by DNA replication will be radioactive. The cell replicates its DNA and divides. Then the daughter cells (still in the radioactive medium) replicate their DNA and divide, and a total of four cells are present. Sketch the DNA molecules in all four cells, showing a normal (nonradioactive) DNA strand as a solid line and a radioactive DNA strand as a dashed line.

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Textbook Question

Researchers working on the Human Genome Project have determined the nucleotide sequences of human genes and in many cases identified the proteins encoded by the genes. Knowledge of the nucleotide sequences of genes might be used to develop lifesaving medicines or treatments for genetic defects. In the United States, both government agencies and biotechnology companies have applied for patents on their discoveries of genes. In Britain, the courts have ruled that a naturally occurring gene cannot be patented. Do you think individuals and companies should be able to patent genes and gene products?

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Textbook Question

A mutation in a single gene may cause a major change in the body of a fruit fly, such as an extra pair of legs or wings. Yet it probably takes the combined action of hundreds or thousands of genes to produce a wing or leg. How can a change in just one gene cause such a big change in the body?

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Textbook Question

A chemical called dioxin is produced as a by-product of some chemical manufacturing processes. This substance was present in Agent Orange, a defoliant sprayed on vegetation during the Vietnam War. There has been a continuing controversy over its effects on soldiers exposed to it during the war. Animal tests have suggested that dioxin can be lethal and can cause birth defects, cancer, organ damage, and immune system suppression. But its effects on humans are unclear, and even animal tests are inconclusive. Researchers have discovered that dioxin enters a cell and binds to a protein that in turn attaches to the cell's DNA. How might this mechanism help explain the variety of dioxin's effects? How might you determine whether a particular individual became ill as a result of exposure to dioxin?

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