40 Questions
Which enzyme is responsible for transcription in both prokaryotes and eukaryotes?
RNA polymerase
In transcription, where does the enzyme bind prior to initiating the process?
Promoter
What is the direction of chain elongation during transcription?
5' to 3'
What drives the polymerization reaction in transcription?
Hydrolysis of a pyrophosphate
In prokaryotes, how many types of RNA polymerase are there?
One
Where are bacterial promoters located relative to the site of initiation?
Upstream
Which RNA polymerase is responsible for transcribing mRNAs in eukaryotes?
RNA polymerase II
What happens to newly transcribed RNAs in eukaryotes?
They are processed
What is the DNA segment corresponding to a primary transcript called?
Transcription unit
Where are rDNA clusters typically found in nondividing cells?
Nucleoli
Which of the following best describes the relationship between genes and proteins according to the text?
Genes store information for producing all cellular proteins.
What did Garrod study in relation to the relationship between genes and proteins?
The relationship between a specific gene, a specific enzyme, and a metabolic condition.
What hypothesis did Beadle and Tatum formulate?
The "one gene–one enzyme" hypothesis.
How was Beadle and Tatum's hypothesis later modified?
To "one gene–one polypeptide chain".
What is the process by which RNA is formed from a DNA template called?
Transcription.
What is the process by which proteins are synthesized in the cytoplasm from an mRNA template called?
Translation.
Which class of RNA recognizes other molecules, provides structural support, and catalyzes chemical reactions?
Ribosomal RNA (rRNA)
What is required to translate information in the mRNA code into amino acids?
Transfer RNA (tRNA)
What is the structure of a bacterial ribosomal RNA?
Circular
How many classes of RNA are there in a cell according to the text?
Three
Which hypothesis did Beadle and Tatum formulate?
The one gene–one polypeptide chain hypothesis
What is the process by which RNA is formed from a DNA template called?
Transcription
What is the structure of a bacterial ribosomal RNA?
rRNA
How many classes of RNA are there in a cell according to the text?
Three
What drives the polymerization reaction in transcription?
RNA polymerase
Where are bacterial promoters located relative to the site of initiation?
Upstream
What happens to newly transcribed RNAs in eukaryotes?
They are exported out of the nucleus
In prokaryotes, how many types of RNA polymerase are there?
One
What did Garrod study in relation to the relationship between genes and proteins?
The relationship between a specific gene and a metabolic condition
What is required to translate information in the mRNA code into amino acids?
tRNA
Which type of RNA polymerase is responsible for transcribing tRNAs in eukaryotes?
RNA polymerase III
What is the function of transcription factors in the process of transcription?
To recognize the promoter
What drives the forward reaction in the polymerization of RNA during transcription?
Hydrolysis of a pyrophosphate
What is the DNA segment corresponding to a primary transcript called?
Transcription unit
What is the function of the sigma factor in prokaryotic transcription?
To recognize the promoter
Where are bacterial promoters located relative to the site of initiation?
Upstream
What are the two conserved regions in bacterial promoters?
Pribnow box and terminator sequence
What is the function of the rho factor protein in bacterial transcription termination?
To assist in termination
What are the enzymatic activities of RNA polymerase?
Digestion of incorrect nucleotides and elongation
Where are rDNA clusters typically found in nondividing cells?
Nucleoli
Study Notes
Transcription
- RNA polymerase is responsible for transcription in both prokaryotes and eukaryotes.
- RNA polymerase binds to the promoter region prior to initiating transcription.
- The direction of chain elongation during transcription is 5' to 3'.
- The polymerization reaction in transcription is driven by the energy released from the breakdown of nucleoside triphosphates.
Prokaryotes
- There is one type of RNA polymerase in prokaryotes.
- Bacterial promoters are located upstream of the site of initiation.
- The sigma factor is necessary for the initiation of transcription in prokaryotes.
Eukaryotes
- RNA polymerase II is responsible for transcribing mRNAs in eukaryotes.
- RNA polymerase I is responsible for transcribing rRNAs, and RNA polymerase III is responsible for transcribing tRNAs and other small RNAs.
- Newly transcribed RNAs in eukaryotes undergo several processing steps before they are mature and functional.
RNA Structure and Function
- There are three main classes of RNA: mRNA, tRNA, and rRNA.
- rRNA is typically found in clusters in nondividing cells.
- The structure of a bacterial ribosomal RNA is single-stranded.
- RNA recognizes other molecules, provides structural support, and catalyzes chemical reactions.
Gene Expression
- The process of forming RNA from a DNA template is called transcription.
- The process of synthesizing proteins in the cytoplasm from an mRNA template is called translation.
- Translation requires tRNAs, ribosomes, and amino acids.
- The relationship between genes and proteins is that one gene specifies one enzyme.
Historical Background
- Archibald Garrod studied the relationship between genes and proteins, proposing the "one gene-one enzyme" hypothesis.
- Beadle and Tatum formulated the "one gene-one enzyme" hypothesis, which was later modified to the "one gene-one polypeptide" hypothesis.
- The "one gene-one enzyme" hypothesis states that one gene specifies one enzyme, which in turn catalyzes a specific chemical reaction.
Test your knowledge on the relationship between genes and proteins with this quiz based on Chapter 11.1 of Gene Expression: From Transcription to Translation. Explore the early observations made by Garrod and the breakthrough work of Beadle and Tatum in understanding the connection between genes, enzymes, and metabolic conditions.
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