How does the information in a gene get turned into a protein?
Explain how genetic information is expressed through transcription (DNA to mRNA) and translation (mRNA to protein), including the roles of mRNA, tRNA, ribosomes, codons, and the genetic code (GSE SB2.a).
A Georgia Milestones Biology EOC answer on protein synthesis: transcription of DNA into mRNA, translation of mRNA into a protein, the roles of mRNA, tRNA, ribosomes, and codons, and how to read the genetic code from a codon chart.
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What this topic is asking
Standard SB2.a asks how genetic information is expressed: turned from a DNA gene into a working protein. For the Georgia Milestones Biology EOC you must know the two stages, transcription (DNA to mRNA) and translation (mRNA to protein), the roles of mRNA, tRNA, ribosomes, and codons, and how to read a codon chart. Items often give a DNA or mRNA sequence and ask you to transcribe or translate it.
The two stages
The flow of information is often summarized as DNA to RNA to protein. Transcription happens in the nucleus (where the DNA is); translation happens at a ribosome (in the cytoplasm or on the rough ER).
Transcription: DNA to mRNA
In transcription, the DNA double helix opens at the gene, and one strand is used as a template. Free RNA nucleotides pair with the template by RNA base-pairing rules: cytosine with guanine, and adenine with uracil (because RNA has no thymine). The result is a single strand of mRNA that carries a complementary copy of the gene. The mRNA then leaves the nucleus and travels to a ribosome.
Translation: mRNA to protein
At the ribosome, the mRNA is read in groups of three bases. Each group of three is a codon, and each codon specifies one amino acid (or a stop signal).
- The ribosome moves along the mRNA, reading one codon at a time.
- A transfer RNA (tRNA) molecule carries a specific amino acid and has an anticodon (three bases) that pairs with the mRNA codon.
- As each matching tRNA arrives, its amino acid is added to a growing chain.
- A start codon (AUG) begins the chain; a stop codon ends it.
The chain of amino acids then folds into a functional protein.
Try this
Q1. State which process makes mRNA from DNA and which process makes a protein from mRNA. [2 points]
- Cue. Transcription makes mRNA from DNA; translation makes a protein from mRNA.
Q2. Define a codon and state how many bases it contains. [2 points]
- Cue. A codon is a group of three mRNA bases that codes for one amino acid (or a stop signal).
Exam-style practice questions
Practice questions written in the style of GaDOE exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Milestones (style)1 marksDuring which process is a molecule of mRNA made from a DNA template? (A) translation (B) transcription (C) replication (D) respirationShow worked answer →
A 1-point selected-response item on naming the process.
The correct answer is B. Transcription is the process that copies a DNA gene into a complementary strand of mRNA. Translation (A) is the next step, where the ribosome reads the mRNA to build a protein. Replication (C) copies DNA into DNA, and respiration (D) is an energy process. The order to remember is transcription (DNA to mRNA) then translation (mRNA to protein).
Milestones (style)2 marksA DNA template strand reads T A C. Write the mRNA codon transcribed from it, then state what the ribosome and tRNA do with that codon during translation.Show worked answer →
A 2-point item combining transcription and translation.
Transcribing T A C with RNA pairing (A-U, C-G) gives the mRNA codon A U G. During translation, the ribosome reads the codon A U G, and a tRNA with the matching anticodon (U A C) brings the amino acid it carries (A U G is the start codon, methionine), adding it to the growing protein chain. Full points need the correct mRNA codon (A U G) and the idea that a tRNA brings the matching amino acid that the ribosome adds to the protein.
Related dot points
- Describe the structure of DNA and RNA, including the double helix, nucleotides, and complementary base pairing, and compare DNA and RNA (GSE SB2.a).
A Georgia Milestones Biology EOC answer on the structure of DNA and RNA: the double helix, nucleotides (sugar, phosphate, base), complementary base pairing (A-T, C-G, A-U), the antiparallel strands, and the key differences between DNA and RNA.
- Explain the process of DNA replication, including its semiconservative nature, the role of complementary base pairing, and why accurate copying matters (GSE SB2.a).
A Georgia Milestones Biology EOC answer on DNA replication: the semiconservative model, how the strands separate and serve as templates, the role of complementary base pairing and DNA polymerase, when replication happens, and why accuracy matters.
- Construct an argument that mutations (changes in DNA sequence and chromosomal alterations) may result in phenotypic variation, and classify gene mutations as beneficial, harmful, or neutral (GSE SB2.b).
A Georgia Milestones Biology EOC answer on mutations: point mutations (substitution, insertion, deletion), frameshift effects, chromosomal mutations, causes (mutagens and replication errors), and how mutations can be beneficial, harmful, or neutral sources of variation.
- Relate the structure of the four macromolecules (carbohydrates, lipids, proteins, nucleic acids), their monomers, and their functions in carrying out cellular processes (GSE SB1.c).
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- Describe the uses and ethical considerations of biotechnology in forensics, medicine, and agriculture, including genetic engineering, GMOs, gene therapy, cloning, and DNA fingerprinting (GSE SB2.c).
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Sources & how we know this
- Biology Georgia Standards of Excellence (GSE) — Georgia Department of Education (2024)
- Georgia Milestones Biology EOC Assessment Guide — Georgia Department of Education (2024)