Molecular Biology: DNA Replication & Transcription
Molecular biology explores the processes by which genetic information is maintained and expressed in living organisms. DNA replication is the mechanism by which a cell copies its DNA before cell division, ensuring genetic continuity. Transcription is the process where a segment of DNA is used as a template to synthesize messenger RNA (mRNA), which carries genetic instructions from the DNA in the nucleus to the ribosomes for protein synthesis.
Molecular Biology: DNA Replication & Transcription
Molecular biology explores the processes by which genetic information is maintained and expressed in living organisms. DNA replication is the mechanism by which a cell copies its DNA before cell division, ensuring genetic continuity. Transcription is the process where a segment of DNA is used as a template to synthesize messenger RNA (mRNA), which carries genetic instructions from the DNA in the nucleus to the ribosomes for protein synthesis.
💡 Key Takeaways
- Outline the main steps of DNA replication and the roles of helicase, primase, DNA polymerase, and ligase.
- Compare leading- and lagging-strand synthesis (including Okazaki fragments) and how fidelity is maintained during replication.
- Describe transcription basics: RNA polymerase, promoters, initiation, elongation, and termination.
- Highlight how RNA processing differs in eukaryotes (capping, splicing, polyadenylation) and how transcription relates to the central dogma (DNA -> RNA -> protein).
❓ Frequently Asked Questions
What is DNA replication?
DNA replication is the process by which a cell copies its entire genome before cell division so that two daughter cells inherit an identical genetic set. The double helix is unwound and new strands are built using the original strands as templates (semi-conservative), with helicase, DNA polymerase, primase, and ligase playing key roles.
What is transcription?
Transcription is the process by which a segment of DNA is used as a template to synthesize RNA, typically messenger RNA, so that genetic information can be expressed. It is carried out by RNA polymerase and involves promoters and regulatory factors.
How do replication and transcription differ?
Replication copies the entire genome to produce DNA copies for cell division, while transcription copies a gene or region of DNA into RNA to express a product. Replication uses DNA polymerase and occurs during S phase; transcription uses RNA polymerase and occurs when a gene is active.
What is semi-conservative replication?
Semi-conservative replication means each new DNA molecule has one original strand and one newly formed strand, preserving old genetic information while creating a new copy.
What is the difference between leading and lagging strand synthesis?
The leading strand is synthesized continuously toward the replication fork, while the lagging strand is synthesized in short fragments (Okazaki fragments) away from the fork and later joined.