Introduction to Mendelian genetics

• Information passed on from parents to next generation are genes.
• Individuals have 2 copies of each gene, from mother and father, called alleles
• Monohybrid cross is a hybrid of two individuals with homozygous genotypes, which result in opposite phenotype for a certain genotype trait.
• We can use a punnet square to predict the phenotypes of the offspring.
• From Tt, tt, the F1 generation would be Tt, Tt, Tt, Tt
• Genes for a particular trait reside at a different location called locus on a certain chromosome.
• Punnet squres from a Monohybrid cross result in a 3:1 ratio.
• Test cross is when we cross over dominant and recessive traits, we get a 3:1 ratio.
• The Punnett Square shows all possible combinations of gametes that could have been produced by one individual.
• Mendels laws are Dominance and Segregation
• Law of Dominance is the hybrid offspring will only inherit the dominant trait of the phenotype. The alleles that are upressed are recessive traits. The alleles that determine the trait are dominant traits.
• Law of Independent Assortment alleles of genes on non-homologous chromosomes assort independently.
• Law of Segregation is during the production of gametes, two copies of each hereditary factor segregate so that offspring acquire one factor from each parent. Alleles segregate during formation of gamete and reunite randomly during fertilisation.
• Independent assortment is a pair of traits segregating independently of another pair during gamete formation. When this happens, different traits get the equal opportunity to occur together.
• During a dihybrid cross we get a 9:3:3:1 ratio. We cross RY, Ry, rY and ry together.