Genetics Genetics Vocab Genetics the scientific study of

Genetics

Genetics Vocab • Genetics: the scientific study of heredity • Heredity: passing of traits from generation to generation • • Traits: specific characteristics that vary from individual to individual

Genetics Vocab • Genes: segment of DNA that carries the instructions for making traits • Alleles: different forms of a trait (we will use letters to represent the different forms) – Example: • Trait: hair color • Alleles would be: – Blonde – Brown – Black – Red – And any combination in between

Genetics Vocab • Dominant trait: the trait observed when at least one dominant allele for a characteristic is inherited • Recessive trait: a trait that appears only when 2 recessive alleles for the same characteristic are inherited

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

Genetics Vocab • Genotype: the inherited combination of alleles (TT, tt, or Tt) • Phenotype: an organisms physical appearance (Tall, short)

Genetics Vocab • Homozygous: 2 alleles are the same for a trait (TT or tt) • Heterozygous: 2 alleles are different for a trait (Tt)

Mendel • Austrian monk who studied genetics in pea plants • How Mendel did his work: – By cross-pollinating plants by transferring pollen from one plant to the egg cells of another – He crossed a pair of plants with different alleles for a trait

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

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.

Punnett Squares • a table that shows all the combinations of alleles that might result from a genetic cross • Vocab you will need to remember in order to do a punnett square – Alleles, dominant, recessive, homozygous, heterozygous, phenotype, and genotype.

Genetics: The Science of Heredity - Probability and Heredity A Punnett Square The diagrams show 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 Genotypes and Phenotypes Genotypes: ¼ RR 2/4 or ½ Rr ¼ rr Phenotypes: ¾ Round ¼ Wrinkled