Genetics: The Science of Heredity Mendel’s Work Probability and Heredity The Cell and Inheritance The DNA Connection Table of Contents

Genetics: The Science of Heredity Mendel’s Work pg 76 His observations revolutionized the study of HEREDITY He asked why his pea plants had different characteristics

Genetics: The Science of Heredity BEGIN NOTES Mendel’s Laws of Heredity 1.Why Mendel Succeeded a. Gregor Mendel-Father of Genetics b. 1 st studies of heredity-the passing of characteristics (traits) to offspring such as bone structure, and eye color. c. Genetics-Study of Heredity

Genetics: The Science of Heredity Mendel’s Experiment 2.Mendel’s Experiment Crossing Pea Plants A.crossed plants with contrasting traits (Tall and short). B.Controlled the fertilization process of this peas plants. He removed pollen from a flower on one plant and transferred it to another C.Started experiment with Purebred plants (Tall from Tall plants and short from short plants) D.Purebred-organisms are the offspring of many generations that have the same trait.

Genetics: The Science of Heredity - Mendel’s Work Crossing Pea Plants Gregor Mendel crossed pea plants that had different traits. The illustrations show how he did this.

Genetics: The Science of Heredity P Generation (purebred) trait Purebred TallPurebred short TTtt cross fertilization Capital Letter T = Dominate Trait Lower Case Letter t = recessive trait

Genetics: The Science of Heredity 3. The 1 st Generation A.Mendel crossed two plants- 1 tall and 1 short. (purebred Tall and short) called the parental generation (P Generation) B.The off spring from the P Generation were all called the 1 st filial generation(F1 Generation) C.All the offspring were tall (the short plants were totally excluded) WHY???????????????????????????

Genetics: The Science of Heredity F 1 Generation TTtt cross fertilization Created the F 1 Generation Tt, Tt, Tt, Tt All the plants are _________________? Capital Letter T = Dominate Trait Lower Case Letter t = recessive trait

Genetics: The Science of Heredity 4. The 2 nd Generation A.1. Next, Mendel crossed two plants from the F1 Generation B.2. The offspring from this cross are called the 2 nd filial generation (F2 Generation) C.Mendel found that ¾ of the offspring were Tall and ¼ were short (the short plants reappeared).

Genetics: The Science of Heredity F 2 Generation Tt cross fertilization Created the F 2 Generation Tt, TT, TT, tt 3 out of 4 plants are _________________? 1 out of 4 plants are _________________? Capital Letter T = Dominate Trait Lower Case Letter t = recessive trait

Genetics: The Science of Heredity - Mendel’s Work Mendel’s Experiments In all of Mendel’s crosses, only one form of the trait appeared in the F 1 generation. However, in the F 2 generation, the “lost” form of the trait always reappeared in about one fourth of the plants. (DRAW PICTURE BELOW)

Genetics: The Science of Heredity Brain Pop & Quiz Brain Pop Heredity

Genetics: The Science of Heredity Alleles ~Alternate forms of a gene are called alleles. ~Alleles are represented by a one or two letter symbol. (e.g. T for tall and t for short) ~These two alleles are now known to be found on copies of chromosomes-one from each parent.

Genetics: The Science of Heredity - Mendel’s Work Dominant and Recessive Alleles Mendel studied several traits in pea plants.

Genetics: The Science of Heredity Dominant and Recessive Alleles Dominant: A gene that is always express and hides others It is present and the trait always shows up and is always represented by a capital letter. Recessive: A gene that is only expressed when a dominant gene is not present. A recessive trait will only be expressed if both alleles are recessive. They are represented by a lower case letter.

Genetics: The Science of Heredity Genetics Dominant and Recessive Genes A dominant gene will always mask a recessive gene. A “widows peak” is dominant, Widows Peak not having a widows peak is recessive. If one parent contributes a gene for a widows peak, and the other parent doesn’t, the off- spring will have a widows peak.

Genetics: The Science of Heredity Genetics ~Punnet Square - A tool we use for predicting the traits of an offspring ~Letters are used as symbols to designate genes ~Capital letters are used for dominant genes ~Lower case letters are used for recessive genes ~Genes always exist in pairs

Genetics: The Science of Heredity Genetics All organisms have two copies of each gene, one contributed by the father, the other contributed by the mother. Homozygous - Two copies of the same gene Heterozygous - Two different genes

Genetics: The Science of Heredity Genetics For the widows peak: WW - has a widows peak Homozygous dominant Ww - has a widows peak Heterozygous ww - no widows peak Homozygous recessive

Genetics: The Science of Heredity - Probability and Heredity A Punnett Square The diagrams show how to make a Punnett square. In this cross, both parents are heterozygous for the trait of seed shape. R represents the dominant round allele, and r represents the recessive wrinkled allele.

Genetics: The Science of Heredity - Probability and Heredity Phenotypes and Genotypes An organism’s phenotype is its physical appearance, or visible traits, and an organism’s genotype is its genetic makeup, or allele combinations.

Genetics: The Science of Heredity - The Cell and Inheritance Meiosis During meiosis, the chromosome pairs separate and are distributed to two different cells. The resulting sex cells have only half as many chromosomes as the other cells in the organism.

Genetics: The Science of Heredity - The Cell and Inheritance Punnett Square A Punnett square is actually a way to show the events that occur at meiosis.

Genetics: The Science of Heredity - The Cell and Inheritance A Lineup of Genes Chromosomes are made up of many genes joined together like beads on a string. The chromosomes in a pair may have different alleles for some genes and the same allele for others.

Genetics: The Science of Heredity - The DNA Connection Mutations Mutations can cause a cell to produce an incorrect protein during protein synthesis. As a result, the organism’s trait, or phenotype, may be different from what it normally would have been.

Genetics: The Science of Heredity End of Section: Graphic Organizer