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Questions and Answers
A always pairs with __
A always pairs with __
T
G always pairs with __
G always pairs with __
C
What are the three steps in the central dogma of molecular biology?
What are the three steps in the central dogma of molecular biology?
What is the role of RNA in gene expression?
What is the role of RNA in gene expression?
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What is the protein synthesis factory called?
What is the protein synthesis factory called?
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In prokaryotes, control of gene expression occurs at the level of translation.
In prokaryotes, control of gene expression occurs at the level of translation.
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What enzyme is produced by E. coli when lactose is present?
What enzyme is produced by E. coli when lactose is present?
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In eukaryotes, where is pre-mRNA formed?
In eukaryotes, where is pre-mRNA formed?
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What is splicing in the context of gene expression?
What is splicing in the context of gene expression?
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What are transcription factors?
What are transcription factors?
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Study Notes
DNA and RNA Fundamentals
- DNA stands for Deoxyribonucleic acid; RNA stands for Ribonucleic acid.
- DNA is composed of four bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T).
- Purines: A and G; Pyrimidines: C and T.
- A always pairs with T, and G always pairs with C in the DNA structure.
Gene Expression Overview
- DNA contains cellular instructions; proteins execute these functions.
- The central dogma of molecular biology: DNA → RNA → Protein.
- Gene expression involves transcription of DNA into messenger RNA (mRNA) and subsequent translation into proteins.
Translation Process
- mRNA is a template for protein synthesis, utilizing a triplet code (3 nucleotides correspond to one amino acid).
- Transfer RNA (tRNA) serves as a go-between, having a specific tRNA for each amino acid.
- tRNA has an amino acid at one end and a triplet code at the other, pairing with mRNA during translation.
Ribosomes and Protein Synthesis
- Ribosomes are the factories for protein synthesis.
- tRNAs carrying amino acids align at the ribosome to match the sequence specified by mRNA.
Control of Gene Expression
- In prokaryotes, gene expression is primarily controlled at the transcription level.
- In E. coli, the presence of glucose influences whether lactose is metabolized; β-galactosidase is produced only when lactose is available.
Eukaryotic Gene Expression Control
- Eukaryotic gene expression control occurs at various levels, including during processing, transport, and degradation of mRNA.
- Pre-mRNA is formed in the nucleus and modified before entering the cytoplasm for translation.
- Transcription factors mediate transcription initiation in eukaryotic cells.
Alternative Splicing
- Exons can be spliced differently to produce various proteins from the same gene.
- Muscle α-tropomyosin uses 12 exons, generating distinct mRNA variants in different tissues.
Post-Translational Modifications
- Proteins undergo modifications post-translation, affecting their function and lifespan.
- Protein degradation is also a component of gene expression regulation in eukaryotes.
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