Gene Expression and Protein Synthesis
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Gene Expression and Protein Synthesis

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Questions and Answers

What determines the nucleotide sequence in mRNA?

the nucleotide sequence in DNA.

Compared to prokaryotes, what do eukaryotes have in gene expression?

a 3' poly-A tail.

How is the forming polypeptide chain attached to a new amino acid during translation elongation?

a peptide bond with the amino acid on the tRNA in the A site.

What happens after mRNA leaves the nucleus?

<p>translation.</p> Signup and view all the answers

In eukaryotes, where is a receptor protein synthesized if it will be part of the plasma membrane or secreted?

<p>in association with the RER.</p> Signup and view all the answers

Can mutations in DNA be repaired?

<p>can be repaired by DNA polymerases.</p> Signup and view all the answers

What occurs as prokaryotic mRNA is being transcribed?

<p>binding of ribosomes and translation.</p> Signup and view all the answers

What does the effect of a point mutation on an individual depend on?

<p>depends on which amino acid is changed.</p> Signup and view all the answers

What is an operon?

<p>a group of functionally related genes transcribed into one mRNA in prokaryotes.</p> Signup and view all the answers

What is the location of the promoter in relation to the gene that is transcribed?

<p>is upstream of the region of the gene that is transcribed.</p> Signup and view all the answers

What happens if a frameshift mutation causes a stop codon to be inserted into the DNA sequence?

<p>the resulting protein will be too short and non-functional.</p> Signup and view all the answers

What does the genetic code consist of?

<p>one of the 20 amino acids for each codon.</p> Signup and view all the answers

What is an example of a frameshift mutation given the DNA sequence ATGCCCTATCACTGA?

<p>ATGCCCACTATCACTGA.</p> Signup and view all the answers

During elongation of protein synthesis, how does tRNA interact with mRNA?

<p>tRNA with the amino acid that matches its anticodon binds to the codon on the mRNA.</p> Signup and view all the answers

RNA splicing shortens the RNA molecule.

<p>True</p> Signup and view all the answers

How is a new strand of RNA synthesized?

<p>from 5 to 3 like DNA.</p> Signup and view all the answers

Where are proteins that will become part of the plasma membrane or secreted inserted?

<p>be inserted into the rough endoplasmic reticulum after the signal sequence is translated.</p> Signup and view all the answers

When does transcription terminate?

<p>when a hairpin pause stops mRNA synthesis.</p> Signup and view all the answers

What is the purpose of transcription?

<p>copy the information in DNA to mRNA.</p> Signup and view all the answers

Which mutation would shorten the resulting protein?

<p>a nonsense mutation that changed a codon for tyrosine to a stop codon.</p> Signup and view all the answers

How are tRNA molecules charged with amino acids during translation?

<p>an enzyme that binds one type of amino acid and recognizes the correct tRNAs.</p> Signup and view all the answers

Where are codons found and what do they interact with?

<p>are found on mRNA and make hydrogen bonds with tRNA.</p> Signup and view all the answers

What amino acid sequence results from the mRNA sequence AUG-CUG-ACC-GCG?

<p>Met-Leu-Thr-Ala.</p> Signup and view all the answers

AUG is the most common start codon.

<p>True</p> Signup and view all the answers

What does transcription refer to?

<p>DNA to mRNA.</p> Signup and view all the answers

What does translation refer to?

<p>mRNA to protein.</p> Signup and view all the answers

How many amino acids are there?

<ol start="20"> <li></li> </ol> Signup and view all the answers

What occurs during prokaryotic transcription?

<p>there are no leading/lagging strands. a single RNA polymerase unwinds the double helix.</p> Signup and view all the answers

What are the components involved in prokaryotic transcription?

<p>promoter, start site, termination site.</p> Signup and view all the answers

What is the role of the promoter in transcription?

<p>promotes binding of RNA polymerase to the DNA.</p> Signup and view all the answers

What is the template direction during elongation in transcription?

<p>template is 3 to 5, new mRNA 5 to 3.</p> Signup and view all the answers

What signals the termination of transcription?

<p>sequence of DNA that makes a hairpin.</p> Signup and view all the answers

In prokaryotic transcription, translation starts before transcription is done.

<p>True</p> Signup and view all the answers

What happens during eukaryotic transcription initiation?

<p>transcription factors recruit RNA polymerase to the promoter region of DNA.</p> Signup and view all the answers

What do general transcription factors do?

<p>bind promoters.</p> Signup and view all the answers

What do specific transcription factors (e.g., activators) bind to?

<p>enhancers.</p> Signup and view all the answers

What role do silencers play in gene expression?

<p>turn off gene expression.</p> Signup and view all the answers

What is true for transcription in both prokaryotes and eukaryotes?

<p>RNA polymerase binds to the promoter, which is a special sequence on the DNA.</p> Signup and view all the answers

Which factors are involved in transcription in eukaryotes but not in prokaryotes?

<p>transcription factors, enhancers, activators.</p> Signup and view all the answers

What are introns?

<p>in the way they get thrown out.</p> Signup and view all the answers

What are exons?

<p>the ones that gets expressed.</p> Signup and view all the answers

What are the post-transcriptional modifications in eukaryotes?

<p>5' cap, 3' poly A tail, pre-mRNA splicing.</p> Signup and view all the answers

What is the role of small ribonucleoprotein particles (snRNPs) in RNA processing?

<p>form spliceosome.</p> Signup and view all the answers

What is the relationship between codons on mRNA and anticodons on tRNA?

<p>codon on mRNA has a complementary base pair anticodon on tRNA.</p> Signup and view all the answers

What does tRNA stand for?

<p>transfer RNA.</p> Signup and view all the answers

What does charging of tRNA mean?

<p>adding an amino acid.</p> Signup and view all the answers

What is involved in the tRNA charging reaction?

<p>amino acyl to RNA synthetases match tRNA to amino acid by anticodon.</p> Signup and view all the answers

What are ribosomes?

<p>enzyme complexes for translation.</p> Signup and view all the answers

What holds together the anticodon and codon?

<p>hydrogen bonds.</p> Signup and view all the answers

What occurs during the elongation phase of translation?

<p>tRNA binds to A site, peptide bond forms, ribosome moves along mRNA.</p> Signup and view all the answers

What happens when a stop codon is reached during translation?

<p>the cycle continues until a stop codon.</p> Signup and view all the answers

What occurs during termination of translation?

<p>stop codon, ribosome releases the protein.</p> Signup and view all the answers

What does ER stand for?

<p>insulin.</p> Signup and view all the answers

What is protein targeting?

<p>translation in cytosol or on RER.</p> Signup and view all the answers

What is a point mutation?

<p>alter a single base.</p> Signup and view all the answers

What is base substitution?

<p>substitute one nucleotide base for another.</p> Signup and view all the answers

What is a silent mutation?

<p>same amino acid inserted.</p> Signup and view all the answers

What is a missense mutation?

<p>changes amino acids inserted.</p> Signup and view all the answers

What do nonsense mutations result in?

<p>change to stop codon.</p> Signup and view all the answers

The genetic code is considered universal.

<p>True</p> Signup and view all the answers

What constitutes the genetic code?

<p>order of nucleotides in DNA encodes amino acid order.</p> Signup and view all the answers

Which codons signal the termination of translation?

<p>UAA, UGA, UAG.</p> Signup and view all the answers

How many codons can one amino acid make?

<p>one amino acid can make multiple codons.</p> Signup and view all the answers

What happens if one nucleotide is deleted?

<p>frameshift mutation.</p> Signup and view all the answers

What are the consequences of frameshift mutations?

<p>big consequences.</p> Signup and view all the answers

What do chromosomal mutations change?

<p>the structure of a chromosome.</p> Signup and view all the answers

What occurs during duplication in chromosomal mutations?

<p>part of the chromosome is lost.</p> Signup and view all the answers

What does inversion refer to in chromosomal mutations?

<p>part of the chromosome is in reverse order.</p> Signup and view all the answers

What happens during translocation in chromosomal mutations?

<p>part of the chromosome is moved to a new location.</p> Signup and view all the answers

What are mutations a starting point for?

<p>evolution.</p> Signup and view all the answers

What can too much change due to mutations be?

<p>harmful.</p> Signup and view all the answers

Study Notes

Gene Expression and Transcription

  • mRNA nucleotide sequence is determined by the nucleotide sequence in DNA.
  • Eukaryotic gene expression includes a 3' poly-A tail, unlike prokaryotes.
  • Transcription terminates when a hairpin pause stops mRNA synthesis.
  • General transcription factors bind to promoters, which are before the start site on DNA.

Translation and Protein Synthesis

  • Translation occurs after mRNA leaves the nucleus.
  • During elongation, tRNA binds amino acids to mRNA codons via peptide bonds at the A site.
  • Amino acids are delivered to the growing polypeptide chain by charged tRNA associated with the correct amino acid.

Mutations and Their Consequences

  • Point mutations can alter a single base, affecting protein function.
  • Missense mutations change one amino acid, while nonsense mutations introduce a premature stop codon.
  • Frameshift mutations, due to insertion or deletion of nucleotides, lead to significant downstream effects on protein structure.

Prokaryotic vs Eukaryotic Transcription

  • Prokaryotic transcription occurs without leading or lagging strands.
  • Translation in prokaryotes can begin before transcription is completed.
  • Eukaryotic transcription involves initiation, elongation, and termination factors, with more defined termination signals.

Post-Transcriptional Modifications

  • Eukaryotic mRNA undergoes modifications: a 5' cap for stability, a 3' poly-A tail for nuclear export, and splicing to remove introns.
  • Exons are coding regions that are expressed, while introns are non-coding regions that are removed.

Codon and Anticodon Interactions

  • Codons are found on mRNA, pairing with corresponding tRNA anticodons through hydrogen bonds.
  • AUG is the most common start codon, coding for Methionine (Met).

Chromosomal Mutations

  • Chromosomal mutations can alter chromosome structure, consisting of duplication, inversion, or translocation.
  • Duplications result in loss of chromosome parts, inversions cause segments to reverse, and translocations relocate chromosome segments.

Overview of the Genetic Code

  • The genetic code is nearly universal, consisting of codons that correspond to amino acids.
  • Three codons (UAA, UGA, UAG) serve as stop signals during translation, halting protein synthesis.

Protein Targeting and Folding

  • Proteins are synthesized in the cytosol or on the rough endoplasmic reticulum (RER), guided by signal sequences that direct them to the appropriate cellular location.
  • Ribosomes function as enzymatic complexes for translation, facilitating peptide bond formation and tRNA interactions.

Evolution and Mutation

  • Mutations are essential for evolution, creating diversity within populations, although excessive changes can result in harmful effects on individuals.

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Description

Test your understanding of gene expression, transcription, translation, and the effects of mutations on protein synthesis. This quiz covers essential concepts such as eukaryotic gene features, transcription mechanisms, and the types and consequences of mutations. Perfect for biology students looking to reinforce their knowledge.

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