Chapter 4: Genetics The Science of Heredity Section 1: Mendel’s Work

What were the results of Mendel’s experiments, or crosses? Mendel discovery of genes and alleles eventually changed scientists’ ideas about heredity.

What controls the inheritance of traits in an organism? An organism’s traits are controlled by the alleles it inherits from its parents. Some alleles are dominant, while other alleles are recessive.

Heredity The passing of physical characteristics from parent to offspring.

Trait Each different form of a characteristic such as stem height or seed color is called a trait. In humans it would be eye color, or hair color as traits.

Genetics The scientific study of heredity.

Fertilization A new organism begins to form when an egg and a sperm join.

Purebred A purebred organism is the offspring of many generations that have the same trait.

P Generation Scientists call the parent plants the P Generation

F 1 or First Filial The first group of offspring from the P generation are known as the first filial or F1 generation. (Filius and Filia mean daughter or son in Latin)

F2 or Second Filial The second group of offspring (crosses of the F1 generation) are known as the second filial or F2 generation It is at this point that traits from the P generation being to reappear even though they were not seen in the F1 generation

Gene The factors that control a trait.

Alleles The different forms of a gene.

Dominant Allele An allele whose trait always shows up in the organism when the allele is present.

Recessive Allele A recessive allele is always hidden whenever the dominant allele is present.

Hybrid A hybrid is an organism that has two different alleles for a trait. Tt a dominant and recessive allele for a trait.