Cell Structure & Genetics Principles

Cell Structure & Function

• Nucleus: Contains DNA, controls cellular activities.
• Vacuole: Storage compartment for water and other substances.
• Smooth Endoplasmic Reticulum (Smooth ER): Lipid synthesis, detoxification.
• Golgi Apparatus: Processes and packages proteins and lipids.
• Rough Endoplasmic Reticulum (Rough ER): Protein synthesis, modification.
• Ribosome: Site of protein synthesis.
• Cytoplasm: Fluid-filled space within cell, contains organelles.
• Cell Membrane: Separates cell from external environment, regulates passage.
• Mitochondria: Powerhouse of the cell, cellular respiration.
• Lysosome: Contains digestive enzymes, breakdown waste.
• Chloroplast: Site of photosynthesis in plant cells.
• Cell Wall: Rigid outer layer in plant cells, provides support.

Genetics: Principles and Processes

Core Concepts of Genetics

• Genetics: Study of heredity and variation in traits through generations.
• Inheritance: Transmission of genetic traits from parents to offspring, driving evolution.
• DNA: Genetic code, identical in plants and animals, double helix structure, composed of nitrogenous bases.
• Gene: Segment of DNA, contains instructions for protein synthesis.
• Chromosome: Coiled DNA, carrying genetic information for specific traits, varying numbers per species.
• Locus: Position of a gene on a chromosome.
• Centromere: Region of chromosome where sister chromatids attach; divides chromosome into two "arms".
• Sister Chromatids: Identical copies of each chromosome.

Types of Reproduction

• Asexual Reproduction: Identical offspring from a single parent, fast, simple.

  • Mitosis: Cell division in all somatic cells, produces two identical cells.
    • Interphase: Cell growth and DNA replication phases
    • Prophase: Chromosomes condense, nuclear envelope breaks down
    • Metaphase: Chromosomes align at the cell's center.
    • Anaphase: Sister chromatids separate.
    • Telophase: Chromosomes decondense, nuclear envelopes reform.
    • Cytokinesis: Cytoplasm divides, forming two cells.
  • Binary Fission: Simple division in prokaryotes via cell splitting.
  • Spores: Single cells produced by specific cells (spore mother cells).
  • Budding/Fragmentation: New organisms develop from the body of the parent.
  • Cloning: Production of a genetically identical copy of an organism.

• Sexual Reproduction: Combining genetic material from two parents via gametes (sex cells).

  • Meiosis: Cell division producing gamete cells (haploid) from diploid cells.
    • Meiosis I: Reduces chromosome number to half, homologous chromosomes separate.
    • Meiosis II: Sister chromatids separate to create four haploid cells.

• Gamete Formation:

  • Spermatogenesis (male): Four sperm produced from one diploid cell
  • Oogenesis (female): One egg and three polar bodies from one diploid cell.

Genetics of Sex and Inheritance

• Sex: Biological characteristics that differentiate male and female.

• Gender: Cultural and societal roles associated with biological sex.

• Genotype: Genetic makeup (allele combinations).

• Phenotype: Observable traits determined by genotype.

• Karyotype: Visual representation of an organism's chromosomes.

• Homologous Chromosomes: Chromosomes with same genetic information.

• Autosomes: Non-sex chromosomes.

• Sex Chromosomes: Chromosomes that determine sex.

• Diploid: Two copies of each chromosome (2n).

• Haploid: One copy of each chromosome (n).

• Polyploid: Multiple sets of chromosomes (more than 2n)

• Sex Determination:

  • Mammals (XX-XY system)
  • Birds (ZW-ZZ system)
  • Reptiles (Temperature-dependent)
  • Fish (Age or Social structure dependent)
  • Insects (Dependent on fertilization)
  • Earthworms (Hermaphroditic)

Mendelian Genetics

• Gregor Mendel: Developed laws of inheritance through experiments on pea plants..

• Monohybrid Crosses: Crosses involving one trait.

• Law of Segregation: Alleles separate during gamete formation.

• Alleles: Different forms of a gene.

• Dominance: Dominant allele masks the recessive allele's expression.

• Homozygous: Having identical alleles.

• Heterozygous: Having different alleles for a trait.

• Incomplete Dominance: Phenotype is blend of both alleles.

• Codominance: Both alleles are expressed fully.

• Multiple Alleles: More than two alleles for a gene.

• Polygenic Inheritance: Multiple genes control a single trait.

• Dihybrid Crosses: Crosses of two traits simultaneously (F2 Generation)

• Law of Independent Assortment: Alleles of unlinked genes separate independently during gamete formation.

History and Discovery of DNA

• Miescher: Isolated DNA, calling it “nuclein.”
• Levene: Proposed basic structure of nucleotides (sugar, phosphate, base).
• Hammerling: Experiments suggesting nucleus contains genetic information.
• Chargaff: Discovered base-pairing rules (A=T, G=C).
• Avery, MacLeod, McCarty: DNA, not protein, is the “transforming principle” in heredity.
• Hershey-Chase: Further evidence of DNA as the hereditary material.
• Franklin: X-ray diffraction images crucial for Watson and Crick.
• Watson and Crick: Determined the DNA double helix structure.

Mutations

• Mutation: Change in DNA sequence.
  • Spontaneous: Occur naturally during DNA replication.
  • Induced: Caused by environmental factors.
  • Point: Substitution of one base for another.
  • Basepair: A single nucleotide pair is exchanged.
  • Frameshift: Insertion or deletion of a nucleotide (can alter the entire protein sequence).
  • Chromosomal: Changes to whole sections of chromosomes (inversions, translocations, deletions, duplications).
  • Jumping genes (transposons): Segments of DNA that can move around the genome.

Human Genome Project and Epigenetics

• Human Genome Project: Project to map and sequence the human genome.
• Epigenetics: Study of heritable changes in gene expression without changing the DNA sequence.