GENETICS Vocabulary Traits characteristics that are inherited Heredity

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 • Gregor Mendel

Genes and Traits • Genes code for a protein that creates the trait. Genes protein 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).

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

Chromosomes and Genes • G is dominant over g dominant • GG or Gg = a big nose • g is recessive under G recessive • gg = a small nose • Gg = heterozygous (different)(hybrid) heterozygous • GG or gg = homozygous (same)(pure breed) homozygous 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: 2 Tt: 2 tt • 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 F 1 generation: 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: 1. Gene linkage- genes located on the same chromosome will be inherited together. 2. 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