Heredity Notes Chapter 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.