Anatomy and Physiology / Unit 2: Cells and Tissues
2.3 Cell Cycle and Protein Synthesis
Notes
Genes are segments of DNA that code for proteins. DNA is in the nucleus; proteins are made at ribosomes.
- Transcription: DNA is copied into messenger RNA (mRNA) in the nucleus. Translation: ribosomes read mRNA in groups of three bases (codons) and transfer RNA (tRNA) brings the matching amino acids.
- DNA base pairing: A with T, C with G. In RNA, uracil (U) replaces thymine (T).
- The cell cycle: interphase (G1, S where DNA is replicated, G2), then mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis (cytoplasm divides).
- Mitosis makes two genetically identical diploid cells (46 chromosomes in humans) for growth and repair. Cancer results from uncontrolled cell division.
- Example: DNA strand TAC-GGA is transcribed to mRNA AUG-CCU.
Practice
During which phase is DNA replicated?
DNA synthesis occurs in the S phase, so each chromosome has two copies before mitosis.
The DNA template sequence TAC GCT is transcribed. What is the mRNA sequence?
Pair A-U, T-A, C-G, G-C: TAC gives AUG, GCT gives CGA.
Where does translation take place?
Ribosomes read mRNA and assemble amino acids into proteins.
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