Central Dogma: DNA to Protein

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Questions and Answers

How many nucleotides are required to code for a polypeptide chain consisting of 250 amino acids?

  • 750 (correct)
  • 125
  • 250
  • 500

Which of the following accurately describes the roles of transcription and translation in gene expression?

  • Transcription converts proteins into RNA, while translation synthesizes DNA from proteins.
  • Transcription synthesizes RNA from a DNA template, while translation synthesizes proteins from an RNA template. (correct)
  • Transcription converts RNA into DNA, while translation synthesizes proteins from DNA.
  • Transcription synthesizes proteins from a DNA template, while translation synthesizes RNA from a protein template.

A mutation in a gene results in a nonfunctional RNA polymerase. What aspect of gene expression would be directly affected?

  • Replication
  • DNA Repair
  • Transcription (correct)
  • Translation

What is the primary function of tRNA in the process of translation?

<p>To transfer amino acids to the ribosome and match them with the appropriate mRNA codon. (B)</p> Signup and view all the answers

A particular mRNA sequence contains the codon 5'-AUU-3'. What tRNA anticodon will bind to this codon?

<p>5'-UAA-3' (C)</p> Signup and view all the answers

If a gene contains introns, what process removes them and what is the result?

<p>RNA Splicing; results in a shorter, continuous coding sequence (D)</p> Signup and view all the answers

What is the role of the start codon (AUG) in translation?

<p>It codes for the amino acid methionine and signals the beginning of translation. (C)</p> Signup and view all the answers

What is the significance of the genetic code being nearly universal?

<p>It suggests a common evolutionary origin for all life forms and allows for gene transfer between species. (C)</p> Signup and view all the answers

Which of the following is a key difference between transcription in prokaryotes and eukaryotes?

<p>Prokaryotic transcription and translation occur simultaneously in the cytoplasm, while eukaryotic transcription occurs in the nucleus and translation in the cytoplasm. (B)</p> Signup and view all the answers

What is the function of the 5' cap and poly-A tail added to eukaryotic mRNA molecules?

<p>They facilitate mRNA export from the nucleus, protect it from degradation, and help ribosomes bind to the mRNA. (B)</p> Signup and view all the answers

What is the function of ribosomes during translation?

<p>To coordinate the interaction between mRNA and tRNA and catalyze the formation of peptide bonds between amino acids (C)</p> Signup and view all the answers

During elongation, what happens when a tRNA molecule's anticodon binds to the mRNA codon in the A site of the ribosome?

<p>The amino acid attached to the tRNA is added to the growing polypeptide chain, forming a new peptide bond. (A)</p> Signup and view all the answers

What event triggers the termination of translation?

<p>A stop codon (UAA, UAG, or UGA) enters the A site of the ribosome. (C)</p> Signup and view all the answers

Which of the following is the correct flow of genetic information in the cell?

<p>DNA → RNA → Protein (A)</p> Signup and view all the answers

How does the sequence of nucleotides in DNA ultimately determine an organism's traits?

<p>The DNA sequence is transcribed into RNA, which is translated into proteins that carry out various functions in the cell. (B)</p> Signup and view all the answers

Which of the following molecules does NOT directly participate in translation?

<p>DNA (D)</p> Signup and view all the answers

Why is the genetic code described as redundant?

<p>Multiple codons can code for the same amino acid. (C)</p> Signup and view all the answers

What would be the most likely effect of a mutation that introduces a premature stop codon into the middle of an mRNA sequence?

<p>The resulting protein would be non-functional or truncated. (B)</p> Signup and view all the answers

What is the function of the promoter region in transcription?

<p>It serves as a binding site for RNA polymerase and determines where transcription starts. (D)</p> Signup and view all the answers

What is the anticodon and where is it located?

<p>The three-base sequence on tRNA that is complementary to an mRNA codon (B)</p> Signup and view all the answers

During translation, the ribosome moves along the mRNA in which direction?

<p>5' to 3' (B)</p> Signup and view all the answers

Assume a transfer RNA (tRNA) molecule is charged with the amino acid alanine. Which of the following would occur once the start codon is recognized?

<p>Alanine will be added immediately after methionine (B)</p> Signup and view all the answers

Which of the following antibiotics inhibits bacterial protein synthesis, while leaving eukaryotic protein synthesis unaffected?

<p>Both B and C (D)</p> Signup and view all the answers

A sequence of DNA has the following template strand: 3'-TTCAGTCGT-5'. What is the corresponding mRNA sequence?

<p>5'-AAGUCAGCA-3' (D)</p> Signup and view all the answers

A particular protein domain consists of 50 amino acids. What is the minimum number of nucleotides in the coding region of the mRNA required to specify this domain?

<p>150 (C)</p> Signup and view all the answers

A gene has a mutation that changes a single nucleotide base pair in the DNA sequence. Which of the following outcomes is least likely?

<p>A frameshift mutation causing a major alteration of the amino acid sequence (A)</p> Signup and view all the answers

What type of bond connects amino acids to build a polypeptide during translation?

<p>Peptide Bond (D)</p> Signup and view all the answers

In eukaryotic cells, where does translation predominantly occur?

<p>Cytoplasm (C)</p> Signup and view all the answers

What is the name of the large molecular complex that links together the growing chain of RNA nucleotides during transcription?

<p>RNA Polymerase (C)</p> Signup and view all the answers

What is the full name of the molecule that carries genetic information from DNA and conveys it to ribosomes, where the information is translated into amino acid sequences?

<p>mRNA (C)</p> Signup and view all the answers

What is the minimum number of nucleotides needed to code for 210 amino acids?

<p>630 (C)</p> Signup and view all the answers

Why is RNA splicing a necessary step in eukaryotic mRNA processing?

<p>To remove noncoding regions (introns) and join coding regions (exons). (D)</p> Signup and view all the answers

If the sequence of bases in a gene is considered its genotype, what is the phenotype a direct result of?

<p>The sequence of amino acids in a protein. (D)</p> Signup and view all the answers

During translation, what would happen if a tRNA molecule with the anticodon 3'-AAG-5' was carrying the wrong amino acid?

<p>An incorrect amino acid would be added to the polypeptide chain. (A)</p> Signup and view all the answers

What is the most likely effect on the protein if a mutation occurs in the terminator sequence of a gene?

<p>The protein will be longer than normal. (B)</p> Signup and view all the answers

Which modification primarily ensures that eukaryotic mRNA is stable enough to be exported from the nucleus and translated in the cytoplasm?

<p>The addition of a poly-A tail at the 3' end and a cap at the 5' end. (A)</p> Signup and view all the answers

During transcription, which strand of DNA is used to synthesize mRNA?

<p>The template strand. (D)</p> Signup and view all the answers

A particular gene codes for a protein with the sequence alanine-proline-glycine. Which of the following mRNA sequences could code for this protein?

<p>5'-GCG-CCA-GGU-3' (C)</p> Signup and view all the answers

Which of the following events signifies the termination of translation?

<p>A release factor binds to a stop codon in the A site of the ribosome. (B)</p> Signup and view all the answers

A mutation in a prokaryotic cell prevents the terminator sequence from functioning correctly. What is the most likely consequence of this mutation during transcription?

<p>Transcription will continue past the end of the gene. (C)</p> Signup and view all the answers

Which of the following components are directly involved in the process of translation?

<p>mRNA, tRNA, ribosomes (D)</p> Signup and view all the answers

Which type of mutation involves the replacement of one nucleotide base pair with another?

<p>Nucleotide substitution (A)</p> Signup and view all the answers

Why might a silent mutation have no observable effect on the phenotype of an organism?

<p>The altered codon codes for the same amino acid as the original codon. (D)</p> Signup and view all the answers

How do frameshift mutations typically lead to nonfunctional polypeptides?

<p>By altering the reading frame and causing subsequent codons to be misread (A)</p> Signup and view all the answers

What is the immediate consequence of a nonsense mutation within a gene?

<p>The protein sequence is prematurely truncated due to the introduction of a stop codon. (A)</p> Signup and view all the answers

How does exposure to UV light or X-rays cause mutations in DNA?

<p>By physically damaging DNA, leading to errors during replication or repair (C)</p> Signup and view all the answers

Why are mutations essential for the process of evolution?

<p>They provide the genetic variation upon which natural selection acts. (A)</p> Signup and view all the answers

AZT, an anti-AIDS drug, is described as a chemical mutagen. How does it cause mutations?

<p>It mimics a DNA base and blocks further replication when incorporated into DNA. (B)</p> Signup and view all the answers

Which of the following best describes the effect of a missense mutation on the protein product?

<p>It changes one amino acid to another, which may or may not affect protein function. (A)</p> Signup and view all the answers

Consider the DNA template sequence 3'-TTCAGTCGT-5'. If a mutation changed the second base from T to C, what type of mutation would this most likely cause?

<p>A nucleotide substitution, which could be silent, missense, or nonsense (B)</p> Signup and view all the answers

In what scenario would a mutation in a gene have the LEAST detrimental effect on an organism?

<p>If it occurs in a non-coding region of the DNA. (C)</p> Signup and view all the answers

Flashcards

Transcription

The synthesis of RNA using a DNA template.

Transfer RNA (tRNA)

A type of RNA that acts as an interpreter in translation. It carries a specific anticodon and amino acid to the mRNA.

Codon

A three-nucleotide sequence in mRNA that specifies a particular amino acid or stop signal.

Translation

The synthesis of a polypeptide using the genetic information encoded in mRNA. It involves changing from the language of nucleotides to amino acids.

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Anticodon

A sequence of three bases on tRNA that is complementary to a specific codon on mRNA, ensuring the correct amino acid is added to the polypeptide chain.

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Start Codon

Specific sequences in mRNA that signal the beginning of protein synthesis. The most common is AUG, which codes for methionine.

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Triplet Code

A set of three-nucleotide 'words' that specify the amino acids for polypeptide chains.

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RNA Polymerase

An enzyme that links together the growing chain of RNA nucleotides during transcription, using a DNA strand as a template.

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Messenger RNA (mRNA)

The type of RNA that carries genetic information from DNA to ribosomes, where it is translated into amino acid sequences.

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RNA polymerase

A large molecular complex that links together the growing chain of RNA nucleotides during transcription.

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Introns

The noncoding regions of RNA that are transcribed but removed before translation.

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Exons

The coding regions of RNA that are joined together to form the continuous coding sequence in mRNA.

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Ribosomes

The cellular structures responsible for protein synthesis.

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Promoter

Special DNA sequences that mark the start of a gene.

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Terminator

Special DNA sequences that signal the end of a gene.

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Mutation

A change in the nucleotide sequence of DNA.

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Nucleotide Substitution

A mutation that replaces one nucleotide with another, potentially altering the encoded amino acid.

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Silent Mutation

A substitution that doesn't change the amino acid sequence due to redundancy in the genetic code.

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Missense Mutation

A mutation that results in one amino acid being replaced by another in the protein.

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Nonsense Mutation

A mutation that changes an amino acid codon to a stop codon, resulting in a truncated protein.

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Frameshift Mutation

Mutation due to insertion or deletion of nucleotides, altering the reading frame.

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Mutagen

Physical or chemical agent that causes mutations.

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Study Notes

  • Genes dictate inherited traits at a molecular level.

Mutations

  • Sickle-cell disease exemplifies how a single amino acid change in a hemoglobin polypeptide can result from a single nucleotide difference in DNA.
  • Mutation involves altering a nucleotide pair.
  • Nucleotide substitution involves replacing one nucleotide and its partner with another pair.
  • Silent mutations: some substitution mutations have no effect on the protein because the new codon codes for the same amino acid.
  • Missense mutations change one amino acid to another, which may or may not impair protein function.
  • Nonsense mutations convert an amino acid codon into a stop codon, leading to premature termination and a non-functional protein.
  • Frameshift mutations result from adding or subtracting nucleotides in a non-multiple of three, altering the reading frame
  • Frameshift mutations often produce nonfunctional polypeptides.
  • Mutations can arise spontaneously during DNA replication or recombination.
  • Mutagens are physical or chemical agents that cause mutations.
  • High-energy radiation (X-rays, UV light) represents a physical mutagen.
  • Chemical mutagens disrupt DNA replication due to structural similarities to DNA bases.
  • AZT, an anti-AIDS drug, acts as a chemical mutagen by mimicking thymine and blocking further replication.
  • While most mutations are harmful, some can enhance the success of an organism.
  • Mutations are crucial for generating genetic diversity, essential for evolution by natural selection.

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