Genetics: The Science of Heredity

Mendel’s WorkChapter 3Section 1

Heredity

• The set of chromosomes that an offspring receives from its parents

• Genetics– The study of heredity

Gregor Mendel

• European Monk– 1800’s

• Bred pea plants– “Father of Genetics”

Pollination

• Self-Pollination– Pollen fertilizes egg

cells of the same flower

• Cross-Pollination– Pollen from one flower

fertilizes egg cells of another flower

Traits

• A characteristic that distinguishes one individual from another

• Mendel’s Seven– Seed shape– Seed color– Seed coat color– Pod shape– Pod color– Flower position– Plant height

Hybrids

• An offspring of parents with different characteristics

• P-generation– parents

• F1-generation– The first generation of

offspring

• F2-generation– The second generation

of offspring

Genes

• The unit that determines traits

• Examples…– Tall or short– Red or blonde hair– Freckles or no freckles

Alleles

• The different forms of a gene

• Eye alleles…– Blue– Brown– Green

Dominant vs. Recessive

• Dominant– The allele that is

expressed• “T” = tall

– CAPITAL LETTER!!!

• Recessive– The allele that is not

expressed• “t” = short

– Lower case letter

Homozygous vs. Heterozygous

• Homozygous– TT

• Both genes are for the tall gene

– tt• Both genes are for the

short gene

• Heterozygous– Tt

• The 2 alleles are different