Question

what is the relationship between dna and proteins

Answer 1

Short answer: DNA contains genes that specify the sequences of amino acids in proteins. Through transcription and translation (the "central dogma"), the nucleotide sequence of a gene is used to make an mRNA, and the mRNA sequence is read as codons that direct ribosomes to build a specific protein. Proteins carry out most cellular functions, so DNA indirectly determines a cell’s structure and behavior.

Details, briefly:
- DNA = long molecule made of nucleotides (A, T, C, G). Genes are stretches of DNA that encode proteins (or functional RNAs).
- Transcription: a gene’s DNA sequence is copied into messenger RNA (mRNA).
- RNA processing (in eukaryotes): introns removed, exons spliced; alternative splicing can create different proteins from one gene.
- Translation: ribosomes read mRNA in three-nucleotide codons; each codon specifies an amino acid (genetic code). tRNAs bring the appropriate amino acids and the ribosome links them into a polypeptide chain.
- Folding and modification: the chain folds into a functional protein and may be chemically modified (phosphorylation, glycosylation, etc.).
- Function and feedback: proteins act as enzymes, structural components, transporters, receptors, signaling molecules, and regulators of gene expression. Many proteins (transcription factors, histones, repair enzymes) influence DNA activity and integrity.
- Consequences of changes: mutations in DNA can alter the amino-acid sequence and thus protein structure/function, which can change cell behavior or cause disease (e.g., the sickle-cell mutation).

Exceptions/notes:
- Not all DNA encodes proteins; much of the genome is regulatory or noncoding RNA.
- Some processes reverse the flow (reverse transcription in retroviruses).
- The genetic code is nearly universal but has a few variations in mitochondria and some organisms.

In sum: DNA provides the instructions; proteins are the machines and structural components built from those instructions.