Central dogma of biology DNA-RNA-Protein

What is the central dogma of molecular biology, and who is credited with its discovery?

The central dogma explains how genetic information is transferred and used to build living organisms. It was discovered by Francis Crick and James Watson, and later refined by others such as Marshall Nirenberg. Its simplified definition is: DNA makes RNA makes protein.

What are the three major players in the central dogma, and what are they made of?

• DNA – nucleic acid made of nucleotides, stores genetic information.

• RNA – nucleic acid made of nucleotides, serves as an intermediate carrying information.

• Proteins – made of amino acids, perform structural and functional roles in the cell.

What are the three main processes in the flow of information according to the central dogma?

• Replication – DNA copies itself.

• Transcription – DNA is used to synthesize RNA.

• Translation – RNA is used to synthesize protein.

Why are DNA, RNA, and proteins considered linear polymers, and how is information stored in them?

They are linear polymers because each unit (monomer) is connected to at most two others. Information is stored in the specific sequence of monomers: DNA nucleotides → RNA nucleotides → amino acids in proteins. Each polymer acts as a template for the next.

What is transcription, and what are its three main steps?

Transcription is the process of converting DNA into messenger RNA (mRNA). It occurs in three steps: initiation, elongation, and termination.

What happens during the initiation step of transcription?

RNA polymerase binds to the promoter region of DNA. In eukaryotic DNA, this includes the TATA box (TATAAA), located ~25 nucleotides upstream from the transcription start site. The DNA strands then separate to allow RNA polymerase to begin synthesis.

How does elongation occur during transcription?

RNA polymerase builds the mRNA strand in the 5′ to 3′ direction, while reading the DNA template strand in the 3′ to 5′ direction. The template (antisense) strand is used to build mRNA, while the non-template (sense/coding) strand matches the mRNA sequence (except U replaces T).

What happens during termination and post-transcriptional modification of mRNA?

RNA polymerase and the mRNA strand detach from DNA. Modifications include:

• A 5′ cap is added.

• A Poly-A tail is added at the 3′ end (by poly-A polymerase).

• RNA splicing removes introns (noncoding regions) and retains exons (coding regions) to form mature mRNA.

What is translation, and what are its three main steps?

Translation is the process of using mRNA to construct a protein. It occurs in three steps: initiation, elongation, and termination.

What is the ribosome structure, and what are the three binding sites for tRNA?

The ribosome is composed of a small subunit and a large subunit. It has three binding sites for tRNA:

• A site (Aminoacyl site) – entry of new tRNA.

• P site (Peptidyl site) – holds tRNA with the growing polypeptide chain.

• E site (Exit site) – where tRNA exits the ribosome.

What occurs during initiation of translation?

mRNA leaves the nucleus and enters the cytosol. The ribosome assembles around the mRNA. The start codon (AUG) is recognized, and the corresponding tRNA anticodon (UAC) brings the methionine amino acid, entering at the P site.

What happens during elongation of translation?

New tRNA molecules enter the A site with amino acids. Peptide bonds form between amino acids. The ribosome shifts:

• tRNA in the P site moves to the E site and exits.

• The polypeptide chain grows and extends from the ribosome.

How does translation termination occur?

Stop codons (UAA, UAG, UGA) do not code for tRNA. When read, a release factor enters the A site. Ribosomal subunits disassemble, and the completed protein is released.

What happens to proteins after translation?

Proteins are transported to the Golgi body, where they undergo folding and modification to form functional proteins.