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Gregor Mendel- Father of Genetics. Mendel’s Methods. Monohybrid crosses - an experimental cross between individuals that differ by a single trait. First generation (F 1 ). Mendel’s F 1 Observations. One of the traits could be seen in the F 1 generation= Dominant
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Mendel’s Methods • Monohybridcrosses- an experimental cross between individuals that differ by a single trait. • First generation (F1).
Mendel’s F1 Observations • One of the traits could be seen in the F1 generation= Dominant • One of the traits was hidden in the F1 generation= Recessive 100% Purple
Genetic Terminology #1 • Phenotype- an organisms traits. • Genotype- an organisms genetic makeup. • Homozygous- identical alleles for a gene. • Heterozygous- two different alleles for a gene.
Genetic Terminology #2 • Gene- a sequence of DNA that codes for a protein. • Allele- one of 2 or more alternative forms of the same gene.
Mendel’s F2Observations • Flower color • Purple:white 705:224 3:1
Mendel’s Dihybrid Cross • 315:108:101:32 = 9:3:3:1
Mendel’s Work Yielded These Genetic Rules • Alternative versions of genes (different alleles) account for variations in inherited characters. • For each character, an organism inherits two alleles, 1 from the mother and 1 from the father. • If two alleles differ, then one, the dominant allele is fully apparent in the organism’s appearance. • The two alleles for each trait segregate during gamete production. • Alleles of a gene segregate independently of the alleles of other genes.
Punnett Square • Punnett square- a diagram used to predict the result of a genetic cross.
Complete Dominance • The dominant allele produces a functional protein and the protein’s effects are apparent. • The recessive allele produces a less functional protein or none at all and the trait is not apparent.
Codominance • Codominance- the effects of both alleles are apparent.
Incomplete Dominance • Incomplete dominance- inheritance in which the F1 is intermediate in phenotype between the parents. • Neither allele is dominant.
Continuous Variation is the result of Polygenic Inheritance • Continuous variation- a gradation in phenotype; indicates that a trait is controlled by two or more genes.
