Mendel…….. The Father of Genetics

Mendel (1866) Austrian Monk Gardener & Mathematician / Statistician Bred pea plants for different traits Pea plants self-pollinate so all the pea plants in a patch would all have the same genes = true breeding

Mendel discovers each parent has 2 copies of gene Different versions of gene Mendel discovers dominant & recessive Law of segregation Law of independent Assortment Sources of variation

Gene = DNA code for one protein Protein causes trait Trait = characteristic = phenotype

Alleles = versions of a gene For example if the gene is height the alleles are tall and short If the gene is seed color the alleles are green and yellow If alleles are blue and brown the gene could be eye color

Dominant vs. Recessive Alleles Dominant alleles over shadow recessive alleles if an individual gets one of each Dominant alleles … use a Capital letter Recessive alleles …use a lower case letter For height Tall is dominant & short is recessive Tall = H short = h the gene is height Same gene must use the same letter of the alphabet

Genotype vs. Phenotype Genotype = what type of alleles you have ex. HH, Hh, or hh Homozygous dominant = HH Homozygous recessive = hh Heterozygous = Hh Phenotype = what type of physical appearance you have short (recessive) or tall(dominant)

Determining phenotype All individuals with even one dominant allele look like the dominant trait The only way to look recessive is to have two copies of the recessive allele hh = looks short Hh = looks tall HH = looks tall

Determining Genotype Any individual that looks recessive has…. 2 recessive alleles (hh) Any individual that looks like dominant trait has: ………at least one dominant allele (H ?) The second allele can only be determined if… ...the individual’s parent or child looks recessive if a parent or child look recessive the individual ……… is heterozygous (Hh)

Generations in genetics experiments P generation = parents (first 2 individuals crossed) F1 generation = offspring of the original parents F2 generation = offspring resulting from a cross of two F1 individuals

Punnett Squares – used to predict the phenotypes / genotypes of offspring

Punnett Square Layout Top & side of box = possible egg/sperm each parent can only give one copy of a gene so egg/sperm can only have one of each letter Squares inside box = possible children (offspring genotypes) so must have 2 of each gene so 2 of each letter Only reflect probability or odds!!!

Probablilty Dad has an X chromosome & a y chromosome What one ( X or y) each child gets is random Do all family's have equal numbers of boys/girls?

Independent assortment = pairs of chromosomes sorted independently Independent assortment = pairs of chromosomes sorted independently. Each pair gets a 50/50 chance of Dads C going to the child.

Types of Crosses Monohybrid looks at one gene Dihybrid looks 2 different genes Each different gene MUST have a different letter of alphabet gene= height T= tall t = short gene = color G = green g= yellow individuals needs 2 of each letter so… TTGG or TtGG or ttGg and so on

Dihybrid Punnett squares All possible gametes on top Heterozygous for both traits makes .. 4 different gametes RrYy parent makes: RY or Ry….rY or ry Each box is a zygote so 2 letter r’s & 2 letter y’s (2 copies of each gene)

Any other parent will not make all 4 gametes so Punnett squares can be smaller

Pedigree = a diagram of a families' genetic history Black circles /squares show individuals with the phenotype being studied If a circle or square is half shaded in … the individual is heterozygous for the trait being studied