Transcript Genetics
Genetics Mendel’s Laws of Heredity Genetics • Heredity: passing of characteristics from parents to offspring. • Traits: the characteristics that are passed to the offspring. Genetics • Genetics: the study of heredity • Gregor Mendel: considered the father of genetics • Mendel worked with peas studying 7 different characteristics 7 traits in Mendel’s peas Genetic Vocabulary Gametes: male and female sex cells In plants: • male gametes are pollen. • female gametes are eggs. Genetic Vocabulary • Fertilization: joining of the male and female gametes. • Zygote: the single cell that results from fertilization • Pollination: transferring pollen to the female reproductive organ. • Gene: segment of DNA that controls a trait. How did Mendel do it? • Mendel worked carefully to pollinate the peas. • Mendel studied one trait at a time. • He worked with true breeding plants. Mendel’s crosses • Mendel crossed a tall plant with a short plant to produce a hybrid. • Hybrid: offspring of parents with different forms of a trait. Identifying Generations • Abbreviations are used for the generations. • P1 – original parents. • F1 – first generation. • F2 – second generation. Mendel’s Crosses • Mendel crossed the offspring of the F1 with itself to produce the F2 generation. • For each trait the ratio in the F2 was the same. Mendel’s Conclusions • Mendel concluded that each trait was controlled by 2 factors. • These factors are genes. • Alleles: alternate forms of a gene. Expressed as different letters. Dominant vs. Recessive • Dominant: an allele that will cover or mask another trait. It is written as a capital letter “T” • Recessive: trait that can be masked by another trait. It is written as a lower case “t” Genetics • Genotype: the genes present in an organism, expressed as 2 letters. • Phenotype: the way an organism looks or behaves Homozygous • Homozygous: an organism is homozygous for a trait if both alleles are the same. • TT is homozygous dominant • tt is homozygous recessive Heterozygous • Heterozygous: an organism is heterozygous for a trait if the 2 alleles are different. • Tt is heterozygous for height. • The dominant allele will be expressed.