Overview
This topic explores how cells grow, divide, and pass on genetic material. It covers the mechanics of mitosis and meiosis, as well as the molecular biology behind DNA replication, transcription, and translation. These processes are critical to growth, reproduction, and heredity.
Key Concepts and Structures
- Mitosis: A form of asexual cell division in somatic (body) cells that results in two genetically identical daughter cells. Phases include prophase, metaphase, anaphase, and telophase, followed by cytokinesis.
- Meiosis: A specialized form of cell division that produces four genetically unique gametes (sperm or eggs), each with half the number of chromosomes. Includes two rounds of division (Meiosis I and II) and processes like crossing over and independent assortment.
- Chromosome Structure: DNA is packaged into chromosomes, each consisting of chromatids connected by a centromere. Humans have 46 chromosomes (23 pairs).
- DNA Replication: A semi-conservative process where DNA unzips and each strand serves as a template for creating a new complementary strand, aided by enzymes like DNA polymerase.
- Central Dogma: The flow of genetic information goes from DNA → RNA → Protein. DNA is transcribed into messenger RNA (mRNA), which is then translated by ribosomes to build proteins.
- Transcription: The process by which a segment of DNA is used as a template to synthesize mRNA inside the nucleus.
- Translation: mRNA travels to the ribosome, where transfer RNA (tRNA) matches amino acids to codons, forming a polypeptide chain (protein).
- Gene Regulation: Not all genes are active all the time. Cells regulate gene expression in response to signals, which is critical for cell specialization and homeostasis.
- Mutations: Changes in DNA sequences that can be silent, harmful, or beneficial. May occur spontaneously or due to environmental factors like radiation or chemicals.
- Genetic Inheritance: Traits are passed from parents to offspring through alleles and follow predictable patterns (dominant, recessive, etc.), as described by Mendelian genetics.
Quick Tip
Remember the difference: Mitosis creates identical cells for growth and repair. Meiosis creates gametes for reproduction. Know the stages and what happens in each, especially crossing over in meiosis I.