Genetics and Heredity

• Heredity: how traits are passed on from one generation to the next
• Mendel: Father of Genetics, discovered the laws of inheritance, discovered that genes are located on chromosomes
• Mendel's Discovery

  • Certain traits dominate others
  • when traits are crossed they become tall and yellow, not a blend of the two
• Law of Segregation: a pair of genes separate or segregate during the formation of sex cells

  • only contain one part of the pair
• Law of Independent Assortment: Alleles of one gene separate independently from the alleles of another gene

  • eye colour does not affect if a person can roll their tongue
• Law of the Principle of Dominance: one gene will always mask the effect of the other gene (Dominant vs Recessive)
• trait: a distinguishing quality or characteristic, typically one belonging to a person
• gene: what controls traits and is found in DNA
• Alleles: different forms of the same gene that are found in different combinations in an individual
• homozygous: having two identical alleles of a particular gene or genes
• heterozygous: having two different alleles of a particular gene or genes
• recessive: relating to or denoting heritable characteristics controlled by genes which are expressed in offspring only when inherited from both parents.
• dominant: allele that is expressed only in the presence of a recessive allele or the same allele (TT, or Tt)
• Phenotype: the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.
• Genotype: The genetic makeup of an organism, including the alleles it carries.
• Punnet squares: A diagram used to show the probability of offspring from a cross.
• Test cross: A cross between two individuals that is used to determine whether a particular trait is dominant or recessive
• Incomplete dominance: when the dominant allele is not fully dominant, and the recessive allele is not fully recessive
• Codominance: when both alleles are expressed in the phenotype. (Heterozygous)
• Multiple Alleles: A gene that has more than two alleles.
• Blood Typing

  • A = I^A I^A , I^A i
  • B = I^B I^B, I^B i
  • AB = I^A I^B
  • O = ii
• Sex Linked Trait: found on a sex chromosome, usually the x and are codominant
• X-linked recessive is more common in males
• Dihybrid Crosses: A cross between two organisms that have two different genes for a particular trait.
• Mapping Chromosomes: The process of determining the location of genes on a chromosome.
• Linked genes: genes that are located close to each other on a chromosome
• Map Distance: The distance genes are from each other on a chromosome
• Cross over frequency: The frequency of crossing over between homologous chromosomes during meiosis.

  • the greater the map distance = more likely to cross over
• Pedigrees: A diagram that shows the inheritance of a trait from one generation to the next.