Who is Gregor Mendel Who is Gregor Mendel and and

What about his Peas?What about his Peas?

•Gregor Johann Mendel Gregor Johann Mendel (1822 – 1884) was an (1822 – 1884) was an Austrian monk who was Austrian monk who was often called often called “the father “the father of genetics.” of genetics.”

•Genetics is the study Genetics is the study how traits are passed how traits are passed from one generation to from one generation to another. another.

Mendel was the first Mendel was the first person to trace the person to trace the

characteristics in a living characteristics in a living thing (pea plants). thing (pea plants).

He then came up He then came up with the idea of with the idea of dominantdominant and and

recessiverecessive traits. traits.

Seven traits of Mendel’s peas1. Flower color is purple or

white2. Flower position is axil or

terminal       3. Stem length is long or short 4. Seed shape is round or

wrinkled5. Seed color is yellow or green6. Pod shape is inflated or

constricted7. Pod color is yellow or green

• By cross-breeding common pea By cross-breeding common pea plants (plants (Pisum sativumPisum sativum) over ) over many generations, Mendel many generations, Mendel discovered that certain traits discovered that certain traits show up in offspring without show up in offspring without any blending of parent any blending of parent characteristics characteristics

•PurebredPurebred - offspring that are - offspring that are the result of mating between the result of mating between genetically similar kinds of genetically similar kinds of parents--the opposite of hybrid.  parents--the opposite of hybrid.  Purebred is the same as true Purebred is the same as true breeding.breeding.

•HybridsHybrids  - offspring that are the - offspring that are the result of mating between two result of mating between two genetically different kinds of genetically different kinds of parents--the opposite of purebred.parents--the opposite of purebred.

• In cross-pollinating plants that either produce yellow or green peas exclusively, Mendel found that the first generation always has yellow peas.   However, the next generation has a 3:1 ratio of yellow to green.

• A 3:1 ratio means the 3 plants will produce yellow peas (Dominant) to 1 plant that will produce green peas (Recessive)

Mendel’s Laws of Inheritance

1.The Law of Dominance2. The Law of Segregation

3. The Law of Independent Assortment

The Law of Dominance

–In a cross of parents that are pure for the same traits, only one form of the trait will appear in the next generation. (YY)

–Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.  (Yy)

The Law of Segregation

  Alleles for a trait are "recombined" at fertilization, producing the genotype for the traits of the offspring.

The Law of Independent Assortment

• Alleles for different traits are distributed to sex cells (& offspring) independently of one another.

Quiz on these notes tomorrow

• Tomorrow, What is a Punnett Square?

• Ticket out the door,

What are Mendel’s three laws of inheritance, use your notes