Biology

• Genetics


  Branch of biology that deals with heredity and variation of organisms
• Chromosomes


  Carry the hereditary information (genes)
• Genetic information flow


  DNA RNA Proteins

  
• Chromosomes


  • Occur in pairs
  • Homologous chromosomes
• Sexual reproduction


  New combinations of genes occur
• Gregor Johann Mendel was an Austrian monk who established the principles of inheritance
• Mendel published his work "Experiments in Plant Hybridization" in 1866
• Mendel's work was largely ignored for 34 years until 1900 when 3 independent botanists rediscovered it
• Mendel was the first biologist to use mathematics to explain his results quantitatively
• Genetics terms


  • Gene
  • Genome
  • Alleles
  • Locus
  • Homozygous
  • Heterozygous
  • Dominant
  • Recessive
  • Genotype
  • Phenotype
  • Monohybrid cross
• Pea plants


  • Easy to cultivate
  • Perfect flower
  • Cross pollination can be done manually
  • Short generation time
  • Pair of contrasting traits
• Mendel looked at seven traits or characteristics of pea plants
• Traits are represented in an organism by at least two factors
• Factors representing the alternate or same form of a character are called alleles
• True-breeding varieties


  Result when self-fertilization produces offspring all identical to the parent
• Hybrid offspring


  Offspring of two different varieties
• Hybridization


  Cross-fertilization of two different varieties
• P generation


  True-breeding parental plants
• F1 generation


  Hybrid offspring
• F2 generation


  Cross of F1 plants
• Mendel's law of segregation describes the inheritance of a single character
• Monohybrid cross


  A cross between two individuals differing in a single character
• Mendel performed a monohybrid cross between a plant with purple flowers and a plant with white flowers
• The F1 generation produced all plants with purple flowers
• A cross of F1 plants with each other produced an F2 generation with 3/4 purple and 1/4 white flowers
• Mendel developed four hypotheses to explain his observations
• Alleles


  Alternative versions of genes that account for variations in inherited characters
• Homozygous genotype


  Has identical alleles
• Heterozygous genotype


  Has two different alleles
• Dominant allele


  Determines the organism's appearance
• Recessive allele


  Has no noticeable effect on the organism's appearance
• Phenotype


  The appearance or expression of a trait
• Genotype


  The genetic makeup of a trait
• The same phenotype may be determined by more than one genotype
• Segregation of alleles


  Allele pairs separate from each other during the production of gametes
• Mendel's hypotheses explain the 3:1 ratio in the F2 generation
• Locus


  The specific location of a gene along a chromosome
• Homozygous individuals


  • Have the same allele on both homologues
• Heterozygous individuals


  • Have a different allele on each homologue
• If the two alleles of a locus differ, then one, the dominant allele, determines the organism's appearance; the other, the recessive allele, has no noticeable effect on the organism's appearance