Genetics

• INHERITED TRAITS/CHARACTERISTICS

  • parent organisms pass traits to their offspring, so they are similar characteristics in both parent and offspring. inherited traits include:

  ability to roll tongue

  attached or unattached earlobes

  dimples or freckles

  naturally curly or straight hair

  hitchhiker’s or straight thumb

  color-blindness or normal vision

  widow’s peak or straight hairline

  color of skin and hair

  cleft or smooth chin
• Hybridization refers to the cross - pollination of two contrasting, true breeding pea varieties (e.g. purple - flowered plants and white - flowered plants)
• P generation (parental generation): true - breeding parents
• F₁ generation (first filial generation): hybrid offspring of P generation
• F₂ generation (second filial generation): produced when F₁ hybrids self - pollinate
• Mendel's Conclusion

  • Dominant Trait vs Recessive Trait

  The "heritable factor" for the recessive trait (white flowers) has not been destroyed, deleted nor blended in the F₁ generation, but was merely masked by the presence of the factor for purple flowers, which is the dominant trait.

  • Further studies

  ✓ Mendel observed the same pattern of inheritance in six other characters, each represented by two distinctly different traits.
• Alleles

  • Alternative versions of a gene account for variation in inherited characters.
• Inheritance of Alleles

  • For each character, an organism inherits two alleles, one from each parent, and the genetic locus is represented twice.
• Principle of Dominance

  • If two alleles at a locus differ, then the dominant allele determines the organism's appearance, while the recessive allele has no noticeable effect on the organism's appearance.
• Law of Segregation

  • It states that two alleles for a heritable character segregate during gamete formation and end up in different gametes.
• Homozygous Allele

  • An organism that has a pair of identical alleles for a character.

  • Example: Homozygous dominant (PP) or Homozygous recessive (pp)
• Heterozygous Allele

  • An organism that has two different alleles for a gene.

  • Example: Heterozygous (Pp)
• Phenotype

  • An organism's appearance or observable traits.

  • Example: PP and Pp plants have the same phenotype (purple).
• Genotype

  • An organism's genetic make up; specific alleles in each chromosome.

  • Example: The genotype of a white flower is pp.