Genetics The study of heredity

Heredity passing traits (characteristics) from parents to their children What you see being passed on Done through the process of meiosis and fertilization

Genes Genes Information on a chromosome that codes for specific traits Come in pairs One from mom and one from dad One is usually more powerful than the other

Alleles Different form of the gene For example: Trait is height Alleles are tall (T) and short (t)

History of Genetics Gregor Mendel Austrian Monk More than 100 years ago Worked with pea plants

Pea Plants Worked with Flower color Flower position Seed color Seed shape Pod shape Pod color Stem length

Mendel’s garden

Types of Traits Dominant Recessive Traits that are more powerful and are the ones you see They are represented by capital letters Recessive Traits that are hidden, or covered up, when there is a dominant trait They are represented by lower case letters

Representing Genes Homozygous This pea plant is short. It inherited 2 genes for shortness – one from the mom and one from the dad. Homozygous Having 2 identical alleles for the same trait This pea plant would be represented by the letters - tt

Representing Genes Heterozygous- Having 2 alleles that are not identical for the same trait This pea plant would be represented by the letters - Tt This tall pea plant has inherited one tall gene from one parent and one short gene from the other parent

Genotypes An organism’s combination of genes for a trait is called its genotype The genotype is represented by letter combinations The possible choices are 2 capital letters, 2 lower case letters or 1 capital letter and 1 lower case letter Examples: TT, tt, Tt

Phenotypes What an organism looks like as a result of its genes (photograph, picture) For example: A pea plant that is TT would look tall, A pea plant that is Tt would look tall, A pea plant that is tt would look short

Time for a Lab Reebops

Punnet Squares Punnet squares are models used to explain genetic crosses The letters across the top and down the left side represent the parents genes

How do you make a Punnet Square? Draw a chart with 4 boxes Across the top put the symbols for the mother’s genotype Down the side put symbols for the father’s genotype Use the cross Aa x Aa –--- A= Round and a = wrinkled

Here is our example Now let’s look at the information inside the boxes. A=purple, a= white What would the phenotype be for the letters AA? What would the phenotype be for the letters Aa? What would the phenotype be for the letters aa?

Incomplete Dominance When a heterozygous genotype (Rr) shows a new phenotype which is in between the two parents A red (RR) snapdragon crossed with a white (rr) snapdragon gives you a pink (Rr) snapdragon

Incomplete Dominance The Punnet square example. Note the new genotypic ratios. 1:2:1