Gregor Mendel “The Father of Genetics” Studied peas: easy and quick to breed, can control mating

Mendel’s Pea Plants Plant Height Seed Color Pod color Green Yellow Short Green Yellow Tall Pod Shape Seed Shape Wrinkled Round Smooth Pinched

Mendel’s Experiments Mendel mated “purebred” plants. (Homozygous) Offspring always looked like parents. X Short Offspring Purebred Short Parents X Purebred Tall Parents Tall Offspring

Mendel’s First Experiment Mendel crossed purebred plants with opposite forms of a trait (like tall x short). X Short Tall All Offspring Tall!

Mendel’s Second Experiment Mendel then crossed two of the offspring from the first experiment. X Tall offspring from 1st experiment 3⁄4 Tall & 1⁄4 Short The short trait showed back up

Dominant and Recessive Genes Mendel concluded that one factor masked the other factor. Alleles that mask or hide other alleles, such as the “tall” allele, are said to be dominant. A recessive allele, such as the short allele, is masked, or covered up, whenever the dominant allele is present.

Mendel’s Law of Segregation Traits exist in different forms and one individual contains 2 alleles for each trait. But only one factor is passed down when egg or sperm are formed—at random. (50-50 chance)

What happens if you cross plants heterozygous for 2 traits? X Yellow Allele Green Allele X Round seed Allele Wrinkled seed allele Yellow seeds are dominant over green and round seeds are dominant over wrinkled seeds.

The first batch of seeds was all round and yellow. But when those plants produced seeds, Mendel got round yellow, round green, wrinkled yellow, wrinkled green.

Law of Independent Assortment Each pair of alleles separate independently of each other in the production of eggs and sperm. So you can get a dominant allele for one trait and dominant for the second—or equally likely, recessive for the second. It’s random for each trait

Thanks, Gregor Mendel