11-1: The Work of Gregor Mendel Biology 2

GENETICS: scientific study of heredity Introduction Every living thing has a set of characteristics inherited from its parent(s) Scientists have discovered that heredity helps understand what makes species unique GENETICS: scientific study of heredity

Became a priest and teacher at monastery Gregor Mendel Gregor Mendel was born in 1822 in Czech Republic Became a priest and teacher at monastery Studied math and science at University of Vienna Was in charge of monastery garden

Mendel was interested in monastery garden peas Gregor Mendel Mendel was interested in monastery garden peas He knew that parts of flowers contain male/female sex cells Stamen produce pollen (Sperm) Pistil produce ovules (Egg)

Gregor Mendel FERTILIZATION: process in sexual reproduction in which male and female reproductive cells join to form a new cell Pea plant flowers are normally self-pollinating Pollen fertilizes ovule of same flower

All the plants that Mendel took care of were true-breeding Gregor Mendel Seeds that are produced by self-pollination inherit all their characteristics from the one parent (true-breeding!) All the plants that Mendel took care of were true-breeding

Gregor Mendel TRUE-BREEDING: term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate In true-breeding, one set would produce only tall plants; one set would produce only purple flowers; etc…

Mendel wanted to produce seeds from different plants Gregor Mendel Mendel wanted to produce seeds from different plants He had to prevent self-pollination He did this by removing the stamen from flowers Used the removed stamen to fertilize other flowers, called cross-pollination Allowed Mendel to study different characteristics

ALLELES: one of a number of different forms of a gene Genes and Dominance TRAIT: specific characteristic that varies from one individual to another Mendel studies 7 different pea plant traits Each of the 7 traits had 2 different “looks” – now called alleles ALLELES: one of a number of different forms of a gene

Offspring are called F1 (first filial) Genes and Dominance Original plants used for fertilization are called P (parental) generation Offspring are called F1 (first filial) Filial = Latin word for son/daughter

HYBRID: offspring of crosses between parents with different traits Genes and Dominance HYBRID: offspring of crosses between parents with different traits After creating hybrid F1 offspring, Mendel studied what the plants looked like Mendel noticed that offspring had characteristics of only 1 parent Other parent characteristics “disappeared”

Genes and Dominance Pg 148 Mendel learned 2 things from his experiments: Biological inheritance is determined by factors that are passed from one generation to the next These factors are now called genes GENES: sequence of DNA that codes for a protein and thus determines a trait

dominant allele will always show dominant trait Genes and Dominance Principle of dominance states that some alleles are dominant and others are recessive. dominant allele will always show dominant trait Recessive allele will only show if there is no dominant allele

Mendel wanted to know if the recessive trait disappeared Segregation Mendel wanted to know if the recessive trait disappeared Allowed all 7 hybrid F1 offspring to produce an F2 generation In F2 generation, recessive showed up again! Figured out that the stronger (dominant) allele “covered up” the weaker (recessive) allele

SEGREGATION: separation of alleles during gamete formation When sex cells (gametes) are created, dominant and recessive alleles have to “separate” from each other GAMETES: specialized cell involved in sexual reproduction

Section Assessment ____________: process in sexual reproduction in which male and female reproductive cells join to form a new cell What does true-breeding mean? What 2 things did Mendel learn from his experiments?

Mendel – From the Garden to the Genome http://www.youtube.com/watch?v=6OPJnO9W_rQ