Introduction to Genetics Genetics = the study of heredity Objectives: E2 - Summarize Mendel’s principle of dominance, identify where the genes that control traits are located, & explain how geneticists use the principles of probability E3 - Predict possible outcomes of various genetic combinations such as monohybrid … inheritance

Gregor Mendel The Father of Genetics carried out important studies of heredity Heredity—the passing on of traits from parents to offspring

Trait- a specific characteristic that is controlled by genes Exp. Eye color, hair color, height

Chromosomes Tightly coiled DNA where your genes are carried Genes Sections of DNA that control your traits

Homologous Chromosomes Chromosomes that are the same size and shape and carry the same genes. You get one from your mother and one from your father that match up. Short pea plant Tall pea plant All tall pea plants 3 tall: 1 short P1P1 F1F1 F2F2

Alleles The different forms a gene can take. (Letters) 2 Types of Alleles: 1. Dominant - Represented by a capital letter (Exp. A) 2. Recessive - Represented by a lower-case letter (Exp. a)

Genotype The combination of two alleles (letters) that represent the genetic make-up of an individual. (AA, Aa, aa) Phenotype The observable physical characteristic of an individual that are the result of its genotype. (Long eyelashes, Blue or Brown eyes)

3 Types of Genotypes: 1. Homozygous Dominant 2 identical alleles that are capitalized (AA, TT) 2. Heterozygous 2 different alleles (Aa, Tt) 3. Homozygous Recessive 2 identical alleles that are lower-case (aa, tt)

Principle of Dominance An organism with a recessive allele for a particular trait will exhibit that form only when the dominant allele for the trait is not present. Organisms with a heterozygous genotype (Aa) will never exhibit the recessive trait because it is hidden (masked) by a dominant allele.

You try this one: AA A a

Etymology Homozygous: homo- (same) + -zygous (joined) Heterozygous: hetero- (other) + -zygous (joined)

Section 1 Check Question 1 The passing on of characteristics from parents to offspring is __________. D. allelic frequency C. pollination B. heredity A. genetics

Section 1 Check Question 2 What are traits? Answer A specific characteristic that is controlled by genes. Height, hair color and eye color are examples of traits in humans.

Section 1 Check Question 3 Gametes are __________. D. fertilized cells that develop into adult organisms C. both male and female sex cells B. female sex cells A. male sex cells

Section 1 Check Question 4 Which of the following genotypes represents a animal that is homozygous dominant for a trait? a. KK b. Kk c. kk

Section 1 Check Question 5 Which of the following genotypes represents a plant that is homozygous recessive for height? C. tt B. Tt A. TT