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Questions and Answers
15.1. What is transcription and where does it occur?
Transcription is the process of transferring genetic information from DNA to RNA. In prokaryotes, transcription occurs in the cytosol, while in eukaryotes, it occurs within the nucleus, chloroplasts, and mitochondria.
15.2. What are the steps of transcription (initiation, elongation, termination)?
The steps of transcription are initiation, elongation, and termination. Transcription starts at the initiation site on DNA, where RNA polymerase binds, proceeds through elongation as RNA polymerase adds nucleotides in the 5’ to 3’ direction, and terminates when RNA polymerase reaches the termination site.
15.3. What is post-transcriptional modification (processing)?
Post-transcriptional modification, or processing, refers to the modifications that mRNA undergoes in eukaryotes before being transported from the nucleus. This includes 5’ capping, 3’ polyadenylation, and removal of introns.
15.4. What is translation and where does it occur?
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15.5. How is the genetic code characterized?
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Study Notes
Transcription
- Transcription is the process of synthesizing RNA from a DNA template.
- Occurs primarily in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells.
Steps of Transcription
- Initiation: RNA polymerase binds to the promoter region of DNA, unwinding the DNA strands to access the template strand.
- Elongation: RNA polymerase moves along the DNA template, adding complementary RNA nucleotides (A, U, C, G) to form a growing RNA chain.
- Termination: The process ends when RNA polymerase reaches a termination signal, releasing the newly synthesized RNA molecule.
Post-Transcriptional Modification (Processing)
- Involves modifications to the RNA transcript before it becomes a functional mRNA.
- Key modifications include the addition of a 5' cap, polyadenylation at the 3' end, and splicing to remove introns while joining exons.
Translation
- Translation is the process of synthesizing proteins from mRNA.
- Occurs in ribosomes, located in the cytoplasm or on the endoplasmic reticulum in eukaryotic cells.
Genetic Code Characterization
- The genetic code is composed of codons, sequences of three nucleotides that correspond to specific amino acids.
- It is universal, degenerate (multiple codons can encode the same amino acid), and has specific start and stop codons to signal the beginning and end of protein synthesis.
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Description
Test your knowledge of protein synthesis with this quiz on transcription and translation. Explore the two essential steps involved in protein synthesis and understand where transcription occurs in the cell.
