How does the information in a gene direct the building of a protein?
Explain how genes are expressed through transcription and translation, how the sequence of DNA bases codes for the sequence of amino acids in a protein, and why this links genotype to phenotype (NYSSLS LS3, structure and function; cause and effect).
A NYSSLS-level answer on protein synthesis for the New York Life Science: Biology Regents: how transcription makes mRNA from DNA, how translation reads codons to build a protein, and how the base sequence of a gene determines a protein and so a trait.
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What this topic is asking
NYSSLS LS3 wants you to explain how a gene is used to build a protein, and how that links the genetic instructions (genotype) to an organism's traits (phenotype). On the Life Science: Biology Regents this usually comes as a cluster where you transcribe a short sequence, identify where translation happens, or explain how the base order determines the protein.
From gene to protein
The information flows DNA to RNA to protein. The protein then does a job (for example as an enzyme), and the proteins a cell makes determine its characteristics. This is why DNA controls the cell.
Transcription
In transcription, the relevant section of DNA unwinds and one strand is used as a template to build a complementary strand of messenger RNA (mRNA). The pairing rule is the same as in DNA except that RNA uses uracil (U) instead of thymine, so adenine on the template pairs with uracil. The mRNA is a mobile copy of the gene that can leave the nucleus and travel to a ribosome.
Translation and the genetic code
In translation, the mRNA is read at the ribosome. The bases are read in groups of three called codons, and each codon specifies one amino acid. Transfer RNA molecules bring the matching amino acids, which are joined in order to build the protein. When the whole mRNA has been read, the finished protein folds into its shape and goes to work. The reading of three-base codons is a clear example of a pattern: a small four-letter alphabet, read in triplets, can specify all 20 amino acids.
Linking genotype to phenotype
Because the base order of a gene sets the amino-acid order of a protein, and the protein's shape sets its function, the genetic instructions (the genotype) produce the organism's characteristics (the phenotype). This is the molecular reason a change in DNA can change a trait: alter a base and you may alter a codon, hence an amino acid, hence the protein, hence the characteristic (see mutations and biotechnology). It is also why cells with the same DNA can differ: they express different genes (see cell differentiation and gene expression).
Try this
Q1. State the two stages of protein synthesis and where each occurs. [2]
- Cue. Transcription (in the nucleus, DNA to mRNA) and translation (at the ribosome, mRNA to protein).
Q2. Explain why a change in the DNA base sequence can change the protein produced. [2]
- Cue. A changed base can change a codon, which may change an amino acid in the protein, altering its shape and so its function.
Exam-style practice questions
Practice questions written in the style of NYSED exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Regents (Life Science sample, 2024)3 marksA short DNA template strand reads T-A-C-G-G-A. (a) Write the mRNA sequence transcribed from it. (b) State where in the cell the mRNA is then translated into a protein. (c) Explain how the order of bases in the gene determines the protein that is made.Show worked answer →
A 3-point constructed-response item assessing structure and function and cause and effect.
(a) 1 point: A-U-G-C-C-U (in RNA, uracil replaces thymine; A pairs with U, T with A, G with C, C with G against the template).
(b) 1 point: at the ribosome (in the cytoplasm).
(c) 1 point: the order of DNA bases sets the order of mRNA bases, which is read in three-base codons; each codon specifies one amino acid, so the base order determines the amino-acid sequence and therefore the protein.
Markers reward the correct mRNA (with U not T) and the chain base order to codons to amino-acid sequence.
Regents (Life Science CR, 2025)2 marksA gene codes for an enzyme. (a) Explain what is meant by gene expression. (b) Explain how a change in one DNA base could change the enzyme produced.Show worked answer →
A 2-point item on gene expression and the genotype-phenotype link.
(a) 1 point: gene expression is the process of using the information in a gene to make a product (a protein), through transcription and translation.
(b) 1 point: a change in one DNA base can change a codon, which may change one amino acid in the enzyme; this can alter the enzyme's shape (active site) and so change or stop its function.
Markers reward defining expression as making a protein from a gene and linking a base change to a changed amino acid and protein.
Related dot points
- Describe the structure of DNA (the antiparallel double helix and base pairing) and explain how complementary base pairing allows DNA to be copied accurately during replication (NYSSLS LS3, structure and function; patterns).
A NYSSLS-level answer on DNA for the New York Life Science: Biology Regents: the double-helix structure, base pairing, why DNA is a stable store of information, and how complementary base pairing allows accurate replication.
- Explain how mutations change the DNA sequence and their possible effects, and describe how genetic technologies such as selective breeding and genetic engineering are used (NYSSLS LS3, cause and effect; structure and function).
A NYSSLS-level answer on mutations and biotechnology for the New York Life Science: Biology Regents: what mutations are and their effects, how they create variation, and how selective breeding and genetic engineering are used and assessed.
- Explain how cells with the same DNA become specialized through differential gene expression, and describe the role of stem cells in development and repair (NYSSLS LS1, structure and function; cause and effect).
A NYSSLS-level answer on differentiation for the New York Life Science: Biology Regents: how cells with identical DNA specialize by expressing different genes, what stem cells are, and how this builds and maintains a multicellular body.
- Use the rules of inheritance (dominant and recessive alleles, genotype and phenotype) and Punnett squares to predict the outcomes of genetic crosses, and interpret pedigrees (NYSSLS LS3, patterns; using mathematics).
A NYSSLS-level answer on inheritance for the New York Life Science: Biology Regents: alleles, genotype and phenotype, dominant and recessive traits, using Punnett squares to predict ratios and probabilities, and reading pedigrees.
- Explain how carbohydrates, lipids, proteins and nucleic acids are constructed from monomers and how the structure of each macromolecule relates to its function (NYSSLS LS1, structure and function).
A NYSSLS-level answer on the chemistry of life for the New York Life Science: Biology Regents: the role of water, the four classes of biological molecule, how monomers join into polymers, and how structure relates to function.
Sources & how we know this
- New York State P-12 Science Learning Standards (Life Science) — New York State Education Department (2016)
- Educator Guide to the Regents Examination in Life Science: Biology — New York State Education Department (2025)