Explain the central dogma of molecular biology (DNA to RNA to Protein)

The central dogma of molecular biology describes the flow of genetic information within a biological system. It outlines how genetic information is transferred from DNA to RNA and ultimately to proteins, which perform various functions in cells.

1. DNA Replication

DNA replication is the first step in the central dogma. During this process, the double helix structure of DNA unwinds and each strand serves as a template for synthesizing a new complementary strand. This ensures that genetic information is accurately passed on during cell division.

Key sub-points:

• Mechanism of Replication: The process involves enzymes like DNA polymerase, which adds nucleotides to form new strands.
• Semiconservative Nature: Each new DNA molecule consists of one old and one new strand, preserving half of the original DNA.
• Origin of Replication: DNA replication begins at specific locations called origins of replication.

2. Transcription

Transcription is the process of synthesizing RNA from a DNA template. In this step, a specific segment of DNA is copied into messenger RNA (mRNA), which carries the genetic information required for protein synthesis.

Key sub-points:

• RNA Polymerase: This enzyme binds to the DNA and separates the strands to synthesize mRNA.
• Post-Transcriptional Modifications: The newly formed mRNA undergoes processing, including the addition of a 5’ cap and a poly-A tail, and splicing to remove introns.
• mRNA Export: Mature mRNA is transported from the nucleus to the cytoplasm for translation.

3. Translation

Translation is the final step where the mRNA is decoded to synthesize proteins. Ribosomes facilitate the translation process, reading the sequence of mRNA codons and assembling the corresponding amino acids to form a polypeptide chain.

Key sub-points:

• Ribosomes: These cellular structures consist of ribosomal RNA (rRNA) and proteins, serving as the site of translation.
• Amino Acids and tRNA: Transfer RNA (tRNA) molecules carry amino acids to the ribosome, matching their anticodons with the mRNA codons.
• Polypeptide Chain Formation: The ribosome facilitates the formation of peptide bonds between amino acids, leading to the production of a functional protein.

Questions to Reinforce Understanding

1. What is the central dogma of molecular biology? It is the process by which genetic information flows from DNA to RNA to proteins.
2. What role does RNA polymerase play? It synthesizes RNA from a DNA template during transcription.
3. How are proteins synthesized? Proteins are synthesized by translating mRNA into amino acids at the ribosome.
4. What is the significance of DNA replication? It ensures that each new cell receives an exact copy of the DNA.
5. What are the differences between mRNA and tRNA? mRNA carries the genetic code, while tRNA brings amino acids to the ribosome.