Georgia Milestones Biology EOC, Molecular Genetics (SB2): a complete overview of DNA and RNA, replication, transcription and translation, mutations, and biotechnology

What the Molecular Genetics domain demands

Molecular Genetics (SB2) is the half of the genetics content that deals with the molecule itself: how DNA stores information, how it is copied, how it is read to make proteins, how it can change, and how we put that knowledge to use. Together with the heredity standard SB3, the genetics standards make up a large share of the Georgia Milestones Biology EOC, near 23 percent. The recurring skills are base pairing (completing strands and codons) and explaining the DNA-to-protein-to-trait chain.

This guide ties together the matching topic pages, each with its own practice questions: DNA and RNA structure, DNA replication, protein synthesis: transcription and translation, mutations and phenotypic variation, and biotechnology and its ethics.

DNA and RNA structure

DNA is a double helix of two strands, each a chain of nucleotides (sugar, phosphate, base). The strands pair by complementary base pairing: A-T and C-G. RNA differs in three tested ways: it is single-stranded, its sugar is ribose, and it uses uracil instead of thymine, so in RNA adenine pairs with uracil (A-U). The complementary structure is what lets DNA be copied and read: each strand specifies the other.

Replication

DNA replication is semiconservative: the helix unwinds, each strand serves as a template, and DNA polymerase builds a new complementary strand against each, giving two identical helices, each with one old strand and one new strand. Accuracy comes from complementary base pairing (only one correct base fits at each position), plus proofreading. Replication occurs during interphase (S phase), before a cell divides, so each daughter cell gets a complete set.

Protein synthesis

Genes are expressed in two stages. Transcription copies a DNA gene into mRNA in the nucleus, using RNA pairing (A-U, C-G). Translation at a ribosome reads the mRNA in codons (three bases each), and tRNA brings the matching amino acid for each codon, building a chain that folds into a protein. The flow is DNA to mRNA to protein. The EOC provides a codon chart when needed; the skill is reading the mRNA in threes from the start codon (AUG).

Mutations and variation

A mutation is a change in DNA. A substitution swaps one base (affecting at most one codon, sometimes silent); an insertion or deletion causes a frameshift that changes every following codon, usually with a large effect. Chromosomal mutations change whole segments or numbers. Mutations matter because DNA codes for proteins, so a sequence change can change a protein and thus a trait. Mutations are the ultimate source of variation and can be beneficial, harmful, or neutral depending on the environment. Only mutations in gametes are inherited.

Biotechnology

Biotechnology applies DNA knowledge. Genetic engineering moves a gene between organisms to make a GMO (pest-resistant crops, insulin-making bacteria); gene therapy adds a working gene to treat a disorder; cloning copies organisms; stem cells may repair tissue; and DNA fingerprinting (gel electrophoresis of DNA fragments) is used in forensics and paternity testing. Each use raises ethical concerns (GMO safety and labeling, DNA privacy, cloning morality, access to therapies), and the EOC expects you to weigh a benefit against a concern.

Check your knowledge

A mix of recall and reasoning questions covering the Molecular Genetics domain. Attempt them under timed conditions, then check against the solutions.

1. State the complementary base pairs in DNA. (1 mark)
2. State three ways RNA differs from DNA. (3 marks)
3. State what "semiconservative" means for DNA replication. (1 mark)
4. Name the process that makes mRNA from DNA and the process that makes a protein from mRNA. (2 marks)
5. Define a codon and state how many bases it contains. (2 marks)
6. A DNA template strand reads T A C. Write the mRNA codon transcribed from it. (1 mark)
7. State which two types of point mutation cause a frameshift. (2 marks)
8. Explain how a mutation in a gene can change an organism's phenotype. (2 marks)
9. Name the biotechnology technique used to compare DNA patterns in forensics. (1 mark)
10. State one benefit and one ethical concern of GMO crops. (2 marks)