GENETICS

Vocabulary Traits – characteristics that are inherited Heredity- passing of characteristics from parents to offspring Genetics – branch of biology that studies heredity Genes- sections of DNA that code for a trait. Gametes- sex cells –

VOCABULARY Alleles – alternative forms of genes (a plant could have alleles for white or purple flowers)

Vocabulary Dominant Trait – trait that is seen more frequently. Upper case letters. RR Recessive Trait – trait that is “hidden”. Lowercase letters rr Phenotype – way an organism looks (ex. Tall or short) Genotype – gene combination. Written using letters. Ex: TT, Tt, tt

Vocabulary Homozygous/Purebreds/True-breeding – both alleles are the SAME. TT (homozygous dominant) or tt (homozygous recessive) Heterozygous/Hybrid – alleles are DIFFERENT Ex: Tt (TALL)

The Father of Genetics- Gregor Mendel

Genes and Traits Genes code for a protein that creates the trait. There can be different versions of a trait. EX: eye color is a trait. Blue Green Brown These are different versions of the trait eye color. Different versions are called alleles.

Chromosomes and Genes Homologous chromosomes – one from mom and one from dad. Both have the same genes but each can have different alleles (different versions of the same gene).

g g g G G G g G Chromosomes and Genes Phenotype=trait=nose size Large allele or small allele Genotype=gene letters=GG G or g Two copies of the gene: GG, Gg, or gg g g g G G G g G

g g G G g g G G Chromosomes and Genes G is dominant over g GG or Gg = a big nose g is recessive under G gg = a small nose Gg = heterozygous (different)(hybrid) GG or gg = homozygous (same)(pure breed) g g G G g g G G

Punnet Squares Tool used to predict outcomes of genetic crosses. Gives us the EXPECTED number. Monohybrid cross: cross involving 1 trait. Dihybrid: cross involving two traits

How to set up and work a Punnett square One set of alleles for a trait go on top of the box and the other set of alleles go on the side of the box. Each letter from the set of alleles is placed on top of the square.

Filling in the boxes… Fill in the top left box with the alleles from top left and upper left. The dominant letter is placed first.

Ok. So what does this mean? Each box represents a possible zygote. The alleles are for a single trait, in this case T is tall and t is short. Tt is the genotype for a heterozygous tall. tt is the genotype for homozygous recessive short. Genotypic ratio: 2Tt: 2tt Phenotypes: 50% chance Tall 50% chance short or 2 Tall: 2 short

More vocabulary Parental Generation/P Generation: Crossing of purebreds to create hybrids. EX: TT x tt Filial generation or F1generation: result of cross between P generation.

Gregor Mendel’s Principles 1. Law/Principle of Dominance- one allele dominates over the other allele. 2. Law/Principle of Segregation- alleles separate (segregate) during gamete formation, making it possible for a recessive trait to re-appear in later generations. 3. Law/Principle of Independent Assortment-different traits are inherited separately; independently separate during Meiosis.

Mendel Con’t *** NOTE: Mendel’s laws/principles did not explain the following: Gene linkage- genes located on the same chromosome will be inherited together. Multiple alleles or polygenic traits. WHY? LACK OF TECHNOLOGY

Chromosome Theory of Inheritance Genes are located on chromosomes and their behavior during Identifies chromosomes as the carriers of genetic material. States that chromosomes, which are seen in all dividing cells and pass from one generation to the next, are the basis for all genetic inheritance