Genetics Genetics = science of heredity, or how we inherit traits from our parents

How genetics began 1866 Gregor Mendel (a monk and plant breeder) published his findings on the method of inheritance Passing of traits on to the next generation = heredity He was successful because of the plants he worked with Pea plants – true breeding plants only produce offspring with one form of a trait Mendel became known as the ”Father of Genetics” Discovered 3 Laws of genetics

Inheritance of traits F2 generation had yellow and a few green seeds!! Mendel noticed that certain varieties of the pea plant produced green seeds and other produced yellow seeds To understand inheritance – Mendel ‘cross-pollinated’ the pea plants Green seeds (y) with yellow seeds (Y) – P (parent) generation What did he find? Offspring of P Generation were all yellow F1 generation What happened to green seeds? Planted F1 generation seeds F2 generation had yellow and a few green seeds!! Decided there must be two forms of genes on the plants = alleles

Dominant vs. Recessive traits Dominant allele = the trait that is always seen when it is present always capital letter Heterozygous or Homozygous Recessive allele = trait that is only seen when it is doubled always lower case letter only homozygous can be hidden Yellow seed color is dominant Green Seed color is recessive

Genotype vs. Phenotype Outward appearance does not always show the genes present in an organism Phenotype = what something looks like Color, height, weight, shape, smell Genotype = allele pairs Homozygous or heterozygous YY or Yy

Mendel’s 3 Laws Law of Dominance: dominant traits are expressed over recessive traits Yellow colors were seen over the green colors Law of Segregation: alleles for each trait are separated during meiosis then reunite during fertilization YY separates so each new daughter cell gets the Y allele Law of Independent Assortment: alleles are distributed randomly during the formation of gametes Specific chromosomes have alleles on them – they are not all related

Punnett Squares Allow us to predict the offspring of a cross between two known genotypes Hybrid – heterozygous organism 2 types Mono-hybrid cross Hybrids of a single trait are crossed Only looking at the patterns of color Di-Hybrid Cross More difficult than mono-hybrid crosses Hybrids of multiple traits Color and size

Father is heterozygous dominant for brown hair Mother is homozygous recessive for blonde hair Create a Punnett square to show their offspring