Questions and Answers
What does the term semiconservative mean with respect to DNA replication?
The 2 DNA molecules created through replication each contain one of the original strands paired with a newly synthesized strand.
What is an origin of replication?
The site on a DNA molecule where specific proteins recognize and bind to initiate replication.
Why are primers required in DNA replication but not in transcription?
DNA polymerases add nucleotides only onto an existing DNA strand and cannot initiate synthesis.
What is a polycistronic mRNA?
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Why is knowing the orientation of a promoter critical when determining the amino acid sequence of an encoded protein?
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What is the function of a sigma factor?
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What is the fate of a protein that has a signal sequence?
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How do some bacteria sense the density of cells in their own population?
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What is the difference between regulation by a repressor and an activator?
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Why is it sometimes difficult to locate genomic regions that encode a protein?
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All of the following are involved in transcription: (Select all that apply)
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All of the following are involved in DNA replication: (Select all that apply)
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All of the following are involved in translation: (Select all that apply)
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Using the DNA strand shown as a template, what will be the sequence of the RNA transcript?
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At which codon will translation likely begin in the given mRNA sequence?
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More than one RNA polymerase can be transcribing a specific gene at a given time.
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More than one ribosome can be translating a specific transcript at a given time.
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Transcription stops at a site called a promoter.
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Some amino acids are coded by more than one codon.
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An enzyme used to synthesize the amino acid tryptophan is most likely:
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Under which conditions will transcription of the lac operon occur?
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All of the following are characteristics of eukaryotic gene expression: (Select all that apply)
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A derivative of lactose serves as an inducer of the lac operon.
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Signal transduction provides a mechanism for cells to sense the conditions of their external environment.
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Quorum sensing allows bacterial cells to sense the density of like cells.
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An open reading frame (ORF) is a stretch of DNA that may encode a protein.
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Study Notes
DNA Replication and Semiconservative Nature
- Semiconservative replication results in two DNA molecules, each containing one original strand and one newly synthesized strand.
- This means half of the original genetic material is conserved in both resultant molecules.
Origin of Replication
- The origin of replication is a specific DNA sequence where replication initiation occurs, recognized by unique proteins.
- Prokaryotic chromosomes and plasmids generally have a singular origin of replication.
Role of Primers in DNA Replication
- Primers are required for DNA replication but not for transcription, as DNA polymerases cannot initiate synthesis without an existing strand.
- Primers provide necessary starting points for DNA polymerase to add new nucleotides.
Polycistronic mRNA in Prokaryotes
- Prokaryotic mRNA can encode one or multiple genes, with polycistronic mRNA carrying several gene sequences.
- Proteins from polycistronic mRNA often have related functions, allowing for coordinated expression of related genes.
Importance of Promoter Orientation
- The orientation of a promoter is crucial for determining the amino acid sequence of the resulting protein.
- Promoters indicate which strand of DNA will be transcribed into RNA, guiding RNA polymerase activity.
Function of Sigma Factor
- The sigma factor is a subunit of RNA polymerase that binds to the promoter to initiate transcription.
- By varying sigma factor production, cells can selectively transcribe different sets of genes as needed.
Fate of Proteins with Signal Sequences
- Proteins containing signal sequences are directed to specific cellular locations or pathways.
Bacterial Cell Density Sensing
- Bacteria utilize quorum sensing to detect cell density, triggering gene expression beneficial at critical population levels.
- Some pathogens exploit this mechanism to regulate genes involved in their virulence.
Regulatory Proteins: Repressors vs. Activators
- Repressors inhibit transcription by binding to a specific DNA segment known as an operator (negative regulation).
- Activators enhance transcription by facilitating RNA polymerase binding or activity (positive regulation).
Challenges Locating Protein-Coding Regions
- Protein-coding regions can be challenging to identify because either DNA strand can serve as a template, creating multiple potential RNA sequences.
- Each strand presents three reading frames, leading to six total possible frames to assess for encoding proteins.
Transcription Components
- Key elements involved in transcription include RNA polymerase, promoters, sigma factors, and uracil.
DNA Replication Components
- Essential components for DNA replication consist of gyrase, DNA polymerase, primase, and primers.
Translation Components
- Important components for translation are ribosomes, start codons, stop codons, and tRNA.
RNA Transcript Sequence
- Given a provided DNA template strand, the resultant RNA transcript sequence is 5' GCGUUAACGUAGGC.
Translation Start Codon
- For the mRNA sequence 5' GCGTTAACGTAGGC, translation will likely initiate at the AUG codon.
Gene Expression Facts
- Multiple RNA polymerases can transcribe the same gene simultaneously.
- Ribosomes can concurrently translate the same mRNA transcript.
- Transcription termination occurs at terminator sequences.
- Some amino acids are represented by multiple codons.
Tryptophan Synthesis Regulation
- The enzyme synthesizing the amino acid tryptophan is typically classified as repressible.
Lac Operon Transcription Conditions
- Transcription of the lac operon occurs when lactose is present and glucose is absent.
Eukaryotic Gene Expression Features
- Eukaryotic gene expression involves adding a 5' cap and a poly-A tail to mRNA, removing introns prior to translation, and starting translation at the first AUG codon.
Additional Statements on Gene Expression and Regulation
- A lactose derivative acts as an inducer for the lac operon.
- Signal transduction mechanisms help cells perceive their external environment.
- Quorum sensing enables bacteria to gauge population density.
- An open reading frame (ORF) is a sequence of DNA likely encoding a protein.
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Description
This quiz covers essential concepts from Chapter 7 of Micro Biology, focusing on DNA replication. Learn about key terms such as semiconservative replication and origins of replication through informative flashcards. Perfect for reinforcing your understanding of molecular biology.
