Chapter 5

Mendel’s Work  Gregor Mendel’s work allowed us to understand why plants and animals are the way they are.  Hereditary is the passing of physical characteristics from parents to offspring.

Mendel’s work continue  Why do some people have blue eyes while others have brown eyes.  Why are some plants tall and some short.  Mendel studied pea plants to learn about traits.  Trait is a characteristic that organisms can pass on to offspring through its genes.

Mendel’s work continue  Mendel experimented by breeding different type of plants together.  These studies founded the studies of genetics.  Genetics is the scientific study of hereditary.

What did he learn  Every trait has different genes and alleles.  Genes are a set of information that controls a trait.  Alleles are the different forms of a gene.  Alleles can be dominant or recessive  Dominant means a trait that always shows up in the organisms  Recessive means a trait is hidden when the dominant allele is present.

Recessive and Alleles  Each gene has two traits.  Dominant genes are labeled with a capital letter like B and recessive genes are labeled with a lowercase letter like b.  A gene can look 3 different ways BB Bb bb

How do we know what color eyes you have  We figure out the possibility of what color eyes you will have by filling out a punnett square.  A punnett square is a chart that shows all the possibility combinations of alleles that can result from a genetic cross.

Punnett Square

Genes  Phenotypes is the physical appearance or visible trait.  Genotypes is the genetic make up or allele combinations.  Homozygous organism has two identical Alleles such as BB or bb  Heterozygous organism has two different Alleles such as Bb.