Introduction to Genetics Mrs. Stewart Biology

Standards: CLE 3210.4.1 Investigate how genetic information is encoded in nucleic acids. CLE 3210.4.2 Describe the relationships among genes, chromosomes, proteins, and hereditary traits. CLE 3210.4.3 Predict the outcome of monohybrid and dihybrid crosses.

Objectives: Differentiate between characteristics and traits Analyze Mendal’s principle of dominance Predict genotype based on phenotype Analyze characteristics and traits in this classroom

Decide with your partner “shoulder” partners decide which one is the cat and which one is the dog. (it’s just a fun way of doing partner teaching without saying partner A and partner B)

What is heredity? The transmission of characteristics from parents to offspring

Heredity is why families look alike

Vocabulary Heredity - The transmission of characteristics from parents to offspring Genetics – the study of heredity Genes – Segments of DNA that code for a characteristic

Characteristics vs. Traits Characteristic – an inheritable feature Examples: flower color, hair color, number of fingers on your hand Trait – a genetically determined variation of a characteristic Examples: purple flower color vs white, brown/blonde/red hair, having 6 fingers instead of 5

Dogs Give your cats two examples of characteristics that can be inherited from human parents to offspring.

Cats Give your dogs an example of traits (variations) for the characteristics he/she listed.

Gregor Mendel (1822-1884) “Father of Genetics” Austrian Monk Studied the inheritance of characteristics & traits using pea plants

Mendel’s pea plants Why pea plants? Pea plants have only 7 chromosomes Can cross pollinate (sexual repro.) or self pollinate (asexual repro.)

Flower Reproduction Reminder:

Self-Pollination Pollen from the plant fertilizes its own eggs Similar to asexual reproduction Creates offspring identical to the parent

Cross - Pollination Mendel removed male parts from one plant to prevent self-pollination and transferred pollen from a plant with different traits Produces “hybrids” Genetically different offspring Sexual reproduction

Dogs Explain the difference between self-pollination and cross-pollination to your cat.

Pea Plant Possibilities Characteristics Traits Seed shape Seed color Seed coat color Pod shape Pod color Flower position Plant height wrinkled or smooth yellow or green white or grey smooth or constricted green or yellow axial or terminal tall or short

Generations The parent generation The first generation The second generation

Mendel’s Observations He recorded the traits for each characteristic in the parent generation and which seeds came from which plants One Observation he made: Sometimes, short plants came from tall plant seeds

Mendel’s experiments Mendel’s Conclusions: P – Purebred Tall x Purebred Short F1 – All tall (hybrids) F2 – 3:1 ratio tall:short Mendel’s Conclusions: Tall height “masks” the effects of short height. Tall is “dominant”; Short is “recessive”.

Genotype VS. Phenotype GENOTYPE: actual combination of alleles (genes) inherited from parents. (One from MOM, and one from DAD.) Example: Tt, TT or tt PHENOTYPE: physical appearance/expression of the trait. Example: Tall plant or short plant

Alleles We use letters to represent the variations Capital Letters = Dominant allele Lowercase letters = recessive allele Example: T = tall plant, t = short plant Most genes have two or more variations (alleles)

Cats and Dogs (think – pair – share) Phenotype Genotype Widows Peak or straight hair line Ww, WW or ww

Important Vocabulary Terms HETEROzygous: (DIFFERENT) have different alleles Example: Tt HOMOzygous : (SAME) have the same alleles. Example: TT or tt HYBRID = offspring of heterozygous parents PUREBRED (true-breeding) = offspring of homozygous parents – will produce offspring identical to parent traits

Principle of Dominance some variations are dominant over others Dominant traits will mask or hide the presence of a recessive trait Recessive traits are hidden/masked by a dominant allele

Principle of Dominance – UFC style Only one can win Matt Hughes = Recessive BJ Penn = Dominant

Principle of Dominance

Cats And Dogs The dominant trait is “gray” fur, and the recessive trait is “white” fur. Lets use the following alleles: Gray is G. White is g. If a bunny is heterozygous gray: What is the genotype? ______________ If a bunny is homozygous white: If a plant is homozygous dominant: Gg gg GG

Principles of Dominance Predictable patterns of dominant and recessive only apply to single gene traits Example: ONE gene is responsible for the type of hairline we have There are 2 alleles (variations) for this gene Possible Phenotypes: widow’s peak (W) or straight hairline (w) Possible Genotypes: WW, Ww or ww

Dominance VS. Commonality Does “dominant” mean most common? Not necessarily Examples: Polydactyl – having 6 fingers Achondroplasia – Dwarfism O blood type (recessive)

Mendel’s 2 Laws Law of Independent Assortment Law of Segregation Homologous chromosomes line up and assort independently during Metaphase/Anaphase I of meiosis Law of Segregation Sister chromatids are sorted into separate gametes during Anaphase II of meiosis

Mendel’s Laws

Cats Explain how the law of independent assortment leads to gametes with different allele combinations

Punnett Squares A diagram that is used to predict the possible outcomes of a particular cross (sexual reproduction union) 

Punnett Squares Each square represents the possible combination of gametes during fertilization to make a baby. 4 gametes for each parent = 4 possible combinations for each trait

Dogs Explain to your cat how Punnett squares work

Objectives: Differentiate between characteristics and traits Analyze Mendal’s principle of dominance Predict genotype based on phenotype Analyze characteristics and traits in this classroom