cell division

• Mitosis


  • Purpose: Growth, repair, and asexual reproduction
  • Number of Divisions: One
  • Daughter Cells: Two
  • Genetic Composition: Identical to parent cell
  • Chromosome Number: Maintained (diploid, 2n)
  • Phases: Prophase, Metaphase, Anaphase, Telophase
  • Crossing Over: None
  • Function in Organisms: Somatic cell division
• Significance of Mitosis


  • Ensures genetic consistency
  • Facilitates tissue growth and maintenance
  • Supports asexual reproduction in some organisms
• Meiosis


  • Purpose: Sexual reproduction
  • Number of Divisions: Two
  • Daughter Cells: Four
  • Genetic Composition: Genetically diverse
  • Chromosome Number: Halved (haploid, n)
  • Phases: Meiosis I: Prophase I, Metaphase I, Anaphase I, Telophase I

  Meiosis II: Prophase II, Metaphase II, Anaphase II, Telophase II

  • Crossing Over: Occurs in Prophase I
  • Function in Organisms: Gamete production (sperm and eggs)
• Significance of Meiosis


  • Enhances genetic variation through recombination
  • Reduces chromosome number for sexual reproduction
  • Maintains species stability across generations
• Gregor Mendel


  Father of genetics; conducted experiments on pea plants (Pisum sativum) to understand inheritance
• Laws of Inheritance


  Developed principles that explain how traits are transmitted from parents to offspring
• Gene


  Unit of heredity; segment of DNA that encodes a trait
• Allele


  Different forms of a gene (e.g., dominant and recessive)
• Locus


  Specific location of a gene on a chromosome
• Genotype


  Genetic makeup of an organism (e.g., AA, Aa, aa)
• Phenotype


  Observable characteristics or traits of an organism
• Homozygous


  Two identical alleles for a gene (e.g., AA or aa)
• Heterozygous


  Two different alleles for a gene (e.g., Aa)
• Law of Segregation


  Each individual has two alleles for each gene, which segregate (separate) during gamete formation, so each gamete carries only one allele
• Law of Independent Assortment

  Genes for different traits can segregate independently during the formation of gametes
• Monohybrid Cross


  A cross between two individuals focusing on one trait
• Monohybrid Cross


  • Cross between two pea plants for seed shape (round vs. wrinkled)
• Punnett Square


  Tool used to predict genotypic and phenotypic ratios
• Genotypic Ratio


  1. 2:1 (e.g., 1 homozygous dominant, 2 heterozygous, 1 homozygous recessive)
• Phenotypic Ratio


  1. 1 (e.g., 3 dominant trait, 1 recessive trait)
• Dihybrid Cross


  A cross between two individuals focusing on two traits
• Dihybrid Cross


  • Cross between pea plants for seed shape and seed color (round yellow vs. wrinkled green)
• Phenotypic Ratio


  1. 3:3:1 (e.g., 9 round yellow, 3 round green, 3 wrinkled yellow, 1 wrinkled green)
• Incomplete Dominance


  Heterozygous phenotype is intermediate between the two homozygous phenotypes (e.g., red and white flowers produce pink offspring)
• Codominance


  Both alleles are expressed equally in the phenotype (e.g., AB blood type)
• Multiple Alleles


  More than two possible alleles exist for a gene (e.g., ABO blood group system)
• Polygenic Inheritance


  Traits controlled by multiple genes (e.g., skin color, height)
• Linked Genes


  Genes located close together on the same chromosome tend to be inherited together
• Significance of Mendelian Genetics


  • Foundation of Genetics: Mendel's principles form the basis of classical genetics
  • Predicting Inheritance: Allows for the prediction of genetic traits in offspring
  • Understanding Variation: Explains genetic variation and mechanisms of inheritance
  • Applications: Used in plant and animal breeding, genetic counseling, and research in genetics and evolutionary biology
• Genes


  Segments of DNA that encode instructions for building proteins, which carry out various functions in the body and determine traits
• Genes


  • Composed of DNA sequences
  • Located on chromosomes
  • Each gene has a specific position, known as a locus
• Alleles


  • Variants of a gene that arise through mutations
  • Can be dominant or recessive, influencing the expression of traits
• Gene expression


  • Genotype determines phenotype through gene expression
  • Environmental factors can influence gene expression
• Gametes


  Reproductive cells (sperm and eggs) that carry half the genetic information of an organism, with one set of chromosomes (haploid, n)
• Gamete formation


  1. Produced through meiosis, which reduces the chromosome number by half

  2. Involves two divisions: Meiosis I and Meiosis II
• Genetic variation


  • Independent assortment and crossing over during meiosis create genetic diversity in gametes
  • Ensures unique combinations of genes in offspring