Ch. 9: Complete Inheritance Essential Standard Bio.3.2.2 Predict offspring ratios based on a variety of inheritance patterns (including dominance, co-dominance, incomplete dominance, multiple alleles, and sex-linked traits).

Genetics Genetics is the field of biology devoted to understanding how characteristics are transmitted from parents to offspring. Genetics was founded by the work of Gregor Johann Mendel, an Austrian monk who experimented with garden peas. The transmission of traits from parents to offspring is known as heredity.

Gregor Mendel Mendel observed seven characteristics of pea plants. He studied each trait individually and grew the plants that were ”pure” for a trait.

Gregor Mendel P generation is where two plants that were pure for a trait (tall and dwarf) are crossed. F1 generation resulted in all tall plants. F2 generation resulted in ¾ tall plants and ¼ dwarf plants.

Complete Inheritance Mendel’s F1 generation ended in only tall plants where the tall trait masked the dwarf trait resulting in tall being the dominant trait over dwarf. The dwarf trait was recessive over the tall trait.

Mendel’s conclusions Law of segregation states that a pair of factors is segregated, or separated, during the formation of gametes Law of independent assortment states that factors for different characteristics are distributed to gametes independently

Genetic Terms Allele = a variation of a gene Genotype = alleles the organisms inherits from the parents that are represented by letters (ex. TT, Tt, or tt) Phenotype = the physical appearance of the organism as a result from the genotype Homozygous = both alleles for a trait are alike (TT or tt) Heterozygous = both alleles for a trait are different (Tt)

Practice!!!! Trait Genotype or Phenotype Homozygous or Heterozygous Dominant or Recessive Widow’s Peak Bb aa Black Fur YY Freckles Phenotype N/A N/A Genotype Heterozygous Dominant Genotype Homozygous Recessive Phenotype N/A N/A Genotype Homozygous Dominant Phenotype N/A N/A

Reginald Punnett Discovered the short-hand way to analyzing possible genotypes in offspring by using Mendel’s Law of segregation. Punnett squares Monohybrid crosses

Punnett Squares Black fur is dominant to brown fur. Two heterozygous black rabbits mated. What are the possible combinations of the offspring?

Testcross A testcross is when an individual of an unknown genotype is crossed with an individual with a known recessive genotype. Ex. Black fur is dominant to brown fur. A black furred rabbit mated with a brown furred rabbit producing six offspring. Four offspring were black furred and two offspring were brown furred. What is the genotype of the black furred parent?