Chapter 17: Gene Expression

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Questions and Answers

What is the main function of RNA in protein synthesis?

To act as a bridge between DNA and protein synthesis (correct)
To transcribe DNA into proteins
To synthesize proteins directly from DNA
To replicate DNA

What is the specific sequence of nucleotides in a gene responsible for?

Terminating translation
Initiating translation
Determining the primary structure of proteins (correct)
Forming peptide bonds

What is the outcome of transcription of a protein-coding gene?

Formation of a peptide bond
Replication of DNA
Production of a messenger RNA (mRNA) molecule (correct)
Synthesis of a protein

What is the nitrogenous base that substitutes for thymine in RNA?

Uracil (C) Signup and view all the answers

What is the sugar molecule found in RNA?

Ribose (A) Signup and view all the answers

What is the process by which DNA directs protein synthesis?

Both transcription and translation (B) Signup and view all the answers

What is the role of nucleotide monomers in DNA or RNA?

To communicate information (C) Signup and view all the answers

What is the outcome of the initiation stage of transcription?

Synthesis of an mRNA molecule (B) Signup and view all the answers

What lies between coding regions in eukaryotic genes and their RNA transcripts?

Introns (C) Signup and view all the answers

What is the purpose of RNA splicing?

To remove introns and join exons to create an mRNA molecule (C) Signup and view all the answers

What is the function of transfer RNA (tRNA)?

To transfer amino acids from the cytoplasmic pool to a growing polypeptide in a ribosome (A) Signup and view all the answers

What is the role of the anticodon on a tRNA molecule?

To base-pair with a complementary codon on mRNA (C) Signup and view all the answers

How does a cell obtain the 20 amino acids available in its cytoplasm?

By either synthesizing them from scratch or taking them up from the surrounding solution (B) Signup and view all the answers

What is the process of translating a genetic message into a polypeptide called?

Translation (D) Signup and view all the answers

What is the result of the process of translation?

A polypeptide chain (A) Signup and view all the answers

How does the genetic message get translated into a polypeptide?

Codon by codon, as tRNAs deposit amino acids in the order prescribed (C) Signup and view all the answers

What is the outcome of the process of translation?

A polypeptide is built (C) Signup and view all the answers

What is the role of initiation factors during initiation of translation?

To bring mRNA and ribosomal subunits together (B) Signup and view all the answers

During elongation, what is the energy source for each addition of an amino acid?

GTP hydrolysis (A) Signup and view all the answers

What is the function of the small ribosomal subunit during initiation of translation?

To bind with the mRNA and initiator tRNA (D) Signup and view all the answers

How does the small ribosomal subunit bind with the mRNA in eukaryotes?

At the 5´ cap of the mRNA (C) Signup and view all the answers

What is the role of GTP hydrolysis during codon recognition?

To increase the accuracy of codon recognition (B) Signup and view all the answers

How many stages are involved in the process of translation?

Three stages (D) Signup and view all the answers

What is the amino acid carried by the initiator tRNA during initiation of translation?

Methionine (B) Signup and view all the answers

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Study Notes

Overview of Gene Expression

Gene expression is the process by which DNA directs protein synthesis, consisting of two stages: transcription and translation
Proteins are the link between genotype and phenotype
RNA is the bridge between DNA and protein synthesis, having a similar structure to DNA but with ribose instead of deoxyribose and uracil instead of thymine

Transcription

During transcription, a DNA strand provides a template for the synthesis of a complementary RNA strand
The process produces a messenger RNA (mRNA) molecule
Transcription of a protein-coding gene produces a complementary RNA strand

Translation

Translation is the process of building a polypeptide, consisting of three stages: initiation, elongation, and termination
All three stages require protein "factors" that aid in the translation process
Initiation involves the binding of mRNA, a tRNA with the first amino acid, and the two ribosomal subunits
The small ribosomal subunit binds with mRNA and a special initiator tRNA, which carries methionine
Elongation involves the addition of amino acids one by one to the growing chain, requiring energy expenditure and codon recognition

RNA Splicing

Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides called introns, which lie between coding regions (exons)
RNA splicing removes introns and joins exons to create an mRNA molecule with a continuous coding sequence
The signal for RNA splicing is a short nucleotide sequence at each end of an intron

Transfer RNA (tRNA)

tRNA molecules are translators, translating a particular mRNA codon into a particular amino acid
Each tRNA molecule bears a specific amino acid at one end and a nucleotide triplet called an anticodon at the other end, which base-pairs with a complementary codon on mRNA
tRNA molecules are transcribed from DNA templates, reading a nucleic acid word (the mRNA codon) and interpreting it as a protein word (the amino acid)