Heredity NotesChapter 3

Mendel and His Peas• Heredity is the passing of traits from parents to offspring.

• Self pollinating plants have both male and female reproductive systems and do not need another plant for reproduction. • When a true breeding plant (no mixed traits), self pollinate the offspring

will have the same traits as the parent.• Cross pollination happens when two plants are mixed in the reproduction

process.• Cross pollination can happen from the wind carrying pollen, animals

brushing from one plant to the next etc.

Mendel continued• Characteristic is a feature that has different form in a population for

example hair color, eye color etc.• Traits are the way that the characteristic is shown for example, brown

hair, blue eyes etc.

Mendel’s First Experiment• In Mendel’s first experiment he crossed purple flowered plants with

white flowered plants, all offspring had purple flowers. This is known as the first generation. • The dominate trait (purple flower) always expresses itself in the first

generation• The recessive trait (white flower) seemed to go away.

Mendel’s Second Experiment• He allowed the first generation plants to self pollinate and the result

was that the recessive trait (white flower) reappear. This set is known as the second generation.• Ratio is the relationship between two different numbers and is often

expressed as a fraction

Traits and Inheritance• Genes are instructions for inherited traits.• Alleles are the different form on the genes, dominant are shown with a capital letter,

recessive with a lower case. Letters are typically chosen by the first letter of the dominant trait. For example Dimples are dominant to non dimples so “D” = dimples, “d” =no dimples

• Phenotype is how the characteristic looks, what you see.• Genotype is how the alleles are expressed (DD, Dd, dd)• Homozygous dominant= 2 capital letters• Homozygous recessive= 2 lower case letters **THE ONLY WAY A RECESSIVE TRAIT WILL BE

SEEN• Heterozygous= 2 mixed letters (Dd) the dominant trait shows.• Punnett Squares are used to show what the offspring will have based on the parent.

• Probability are the chances that something will happen, often written as a fraction.• Incomplete dominance are when traits blend together.• Some traits have several genes acting together for one characteristic

such as hair color, eye color and skin color.• Environment can also factor in to the influence on traits.