Chapter 15 Flashcards
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What are the two main stages of gene expression?
The two main stages of gene expression are transcription and translation.
What is transcription?
Transcription is the process by which RNA is synthesized from a DNA template.
What enzyme is responsible for transcription?
RNA polymerase is the enzyme responsible for transcription.
What is the role of RNA polymerase in transcription?
RNA polymerase pries open the DNA strands and joins RNA nucleotides complementary to the DNA template.
What is a promoter in the context of transcription?
A promoter is a specific sequence of nucleotides on the DNA that indicates the beginning of transcription.
What is the difference between bacterial and eukaryotic transcription initiation?
In bacteria, RNA polymerase binds directly to the promoter, while in eukaryotes, transcription factors assist RNA polymerase II in recognizing and binding to the promoter.
What is the TATA box?
The TATA box is a key DNA sequence often involved in initiating transcription in eukaryotes
What are the three stages of transcription?
The three stages of transcription are initiation, elongation, and termination.
What happens during the elongation stage of transcription?
During elongation, RNA polymerase unwinds the DNA, exposing about 10-20 base pairs at a time, and adds RNA nucleotides in the 5’ to 3’ direction to the growing RNA chain
How does transcription terminate in bacteria?
In bacteria, transcription terminates when RNA polymerase transcribes a terminator sequence on the DNA, signaling the end of transcription.
What is RNA processing in eukaryotes?
RNA processing in eukaryotes involves modifications to the primary RNA transcript, including the addition of protective caps and splicing.
What is added to the 5’ end of the RNA during RNA processing?
A modified guanine nucleotide, known as the 5’ cap, is added to the 5’ end of the RNA.
What is the purpose of the poly-A tail added to the 3’ end of the RNA?
The poly-A tail increases stability, facilitates nuclear export, and assists in translation initiation.
What are introns and exons?
Introns are noncoding sequences in the RNA that are removed during RNA splicing, while exons are coding sequences that are joined together to form a continuous coding sequence.
What is the spliceosome?
The spliceosome is a large protein-RNA complex that catalyzes the splicing process, removing introns and joining exons together.
What is translation?
Translation is the process by which the genetic code in mRNA is used to synthesize a sequence of amino acids, forming a polypeptide.
What are the key components involved in translation?
The key components involved in translation are mRNA, tRNA, and ribosomes.
What is the role of tRNA in translation?
tRNA brings specific amino acids to the ribosome, matching its anticodon with the corresponding mRNA codon.
What are the three binding sites on a ribosome?
The three binding sites on a ribosome are the P site, A site, and E site.
What is the function of the site on a ribosome?
The P site holds the tRNA carrying the growing polypeptide chain.
What is the function of the A site on a ribosome?
The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain.
What is the function of the E site on a ribosome?
The E site is where discharged tRNAs exit the ribosome.
What is the wobble hypothesis?
The wobble hypothesis suggests that the flexibility in the base pairing of the third nucleotide of the codon allows a single tRNA to bind with multiple codons.
What are the three stages of translation?
The three stages of translation are initiation, elongation, and termination.
What happens during the initiation stage of translation?
During initiation, the ribosome binds to the mRNA, and an initiator tRNA (carrying methionine) attaches, forming the initiation complex.
What happens during the elongation stage of translation?
During elongation, the ribosome moves along the mRNA, and tRNA molecules bring amino acids to the ribosome according to the codon sequence, extending the polypeptide chain.
What happens during the termination stage of translation?
During termination, the ribosome encounters a stop codon, releasing the completed polypeptide from the ribosome.
What are post-translational modifications?
Post-translational modifications are changes made to the polypeptide after translation, such as the addition of sugars, lipids, or phosphate groups, and the removal of amino acids from the N-terminus.
What is the role of signal peptides in protein targeting?
Signal peptides direct newly synthesized proteins to the endoplasmic reticulum for transport or secretion.
