5.2 -- Mendel and Heredity

• Traits are distinguishing characteristics that are inherited.
• Genetics is the study of biological inheritance patterns and variations in organisms.
• Our current understanding of heredity and genetics comes from the experiments of Austrian monk Gregor Mendel that laid the foundation.
• Reasons for the which Mendel worked with pea plants:

  • fast reproductive rate
  • many different variations
  • easily control pollination (reproduction)
• Mendel observed a total of seven traits in pea plants.
• The separation of genes during gamete formation is known as the law of segregation.
• A heterozygous genotype has two different alleles for the same gene
• A homozygous genotype has two identical alleles for the same gene
• A genetic cross is the mating of two organisms
• A gene is a piece of DNA that provides a set of instructions to a cell to create a particular protein
• The genotype of the actual genetic makeup of an organism
• The phenotype is the physical and visible characteristics (traits) of an individual
• A dominant allele is the one present when two different or identical alleles are present (capital letter)
• Recessive alleles are only visible when two recessive copies occur together (lowercase letter)
• Simply because an allele is dominant this does not make it the most common.
• Early 1900's, Reginald C. Punnett explored genetic crosses in animals and created the Punnett square.
• Punnett squares are statistical diagrams that can predict possible outcomes (genotypes) of a genetic cross
• A chromosome is one long continuous strand of DNA segments that make up many genes
• Each gene has a locus, or specific position, on a chromosome
• A gene is a segment of DNA