bio 20300 anatomy and physiology unit 5 study guides

Key Concepts

• Cell cycle consists of interphase and mitosis, the process by which cells divide and replicate
• Mitosis produces two genetically identical daughter cells from a single parent cell
• Chromosomes contain genetic material (DNA) and are duplicated during interphase
• Genes are segments of DNA that code for specific traits and are passed from parents to offspring
• Mendel's laws of inheritance (law of segregation, law of independent assortment) explain how traits are inherited
• Genetic variation arises from mutations, crossing over during meiosis, and independent assortment of chromosomes
• Cell division is tightly regulated to ensure proper growth, development, and repair of tissues

Cell Cycle Basics

• Cell cycle divided into interphase and mitosis
• Interphase is the longest phase of the cell cycle, during which the cell grows, performs its normal functions, and prepares for division
  • Interphase consists of three stages: G1, S, and G2
  • G1 (first gap phase): cell grows and carries out normal functions
  • S (synthesis phase): DNA replication occurs, and chromosomes are duplicated
  • G2 (second gap phase): cell continues to grow and prepares for mitosis
• Mitosis is the process of cell division, resulting in two genetically identical daughter cells
• Cytokinesis is the division of the cytoplasm, which occurs after mitosis is complete

Stages of Mitosis

• Prophase: chromosomes condense and become visible, nuclear envelope breaks down, and spindle fibers begin to form
  • Chromosomes consist of two sister chromatids joined at the centromere
• Metaphase: chromosomes align at the equatorial plane of the cell, attached to spindle fibers at their centromeres
• Anaphase: sister chromatids separate and are pulled towards opposite poles of the cell by the spindle fibers
• Telophase: chromosomes decondense, nuclear envelopes re-form around the daughter nuclei, and cytokinesis begins
  • Cytokinesis is the division of the cytoplasm, resulting in two separate daughter cells
• Mitosis ensures that each daughter cell receives an identical set of genetic material

Genetic Material and Chromosomes

• DNA (deoxyribonucleic acid) is the genetic material that carries the instructions for an organism's development and function
• DNA is organized into chromosomes, which are compact structures of DNA and proteins
• Humans have 46 chromosomes (23 pairs) in each somatic cell
  • One chromosome in each pair is inherited from the mother, and the other from the father
• Genes are segments of DNA that code for specific traits or proteins
• Alleles are different versions of a gene that can result in different traits (e.g., eye color)
• Homologous chromosomes are chromosome pairs that carry the same genes but may have different alleles

Regulation of Cell Division

• Cell division is tightly regulated to maintain proper growth, development, and repair of tissues
• Checkpoints throughout the cell cycle ensure that conditions are suitable for the cell to proceed to the next stage
  • G1 checkpoint: ensures that the cell has reached an appropriate size and has no DNA damage before entering S phase
  • G2 checkpoint: ensures that DNA replication is complete and the cell is ready for mitosis
  • Spindle assembly checkpoint: ensures that all chromosomes are properly attached to the spindle fibers before anaphase begins
• Cyclins and cyclin-dependent kinases (CDKs) are proteins that regulate the progression through the cell cycle
  • Specific cyclins and CDKs are active at different stages of the cell cycle
• Tumor suppressor genes (e.g., p53) and proto-oncogenes help regulate cell division and prevent uncontrolled growth

Genetic Inheritance and Variation

• Mendel's laws of inheritance explain how traits are passed from parents to offspring
  • Law of segregation: each individual possesses two alleles for each gene, which segregate during gamete formation
  • Law of independent assortment: alleles for different genes assort independently during gamete formation
• Genotype refers to an individual's genetic makeup, while phenotype is the observable characteristics resulting from the genotype and environmental factors
• Genetic variation arises from mutations, crossing over during meiosis, and independent assortment of chromosomes
  • Mutations are changes in the DNA sequence that can be beneficial, neutral, or harmful
  • Crossing over is the exchange of genetic material between homologous chromosomes during meiosis, resulting in new combinations of alleles
• Genetic disorders can be caused by mutations in single genes (monogenic disorders), multiple genes (polygenic disorders), or chromosomal abnormalities

Practical Applications

• Understanding cell division and genetics is crucial for diagnosing and treating genetic disorders and cancers
  • Genetic testing can identify mutations associated with specific disorders (cystic fibrosis) and guide treatment decisions
• Knowledge of genetics is used in agriculture to develop crops with desirable traits (disease resistance, higher yields)
• Genetic engineering techniques (gene therapy, CRISPR-Cas9) have the potential to treat genetic disorders by modifying or replacing faulty genes
• Studying cell division and genetics helps us understand the basis of inherited traits and the role of genetic factors in human health and disease

Common Misconceptions

• Mitosis and meiosis are not the same process; mitosis produces genetically identical daughter cells, while meiosis produces gametes with half the genetic material
• Dominant alleles do not always "dominate" over recessive alleles; they are expressed when present, while recessive alleles are only expressed when no dominant allele is present
• Acquired characteristics (skills, knowledge) are not inherited; only genetic information is passed from parents to offspring
• Genetic determinism is the incorrect belief that genes alone determine all traits; environment and epigenetic factors also play a role in shaping an individual's characteristics
• Cloning does not produce an exact copy of an individual; while the genetic material may be identical, environmental factors and random events during development can result in differences between clones