6.3 Mendel and Heredity

KEY CONCEPT Mendel’s research showed that traits are inherited as discrete units called genes (made of DNA).

6.3 Mendel and Heredity

Mendel laid the groundwork for genetics.

• Traits are distinguishing characteristics that are inherited.

• Genetics is the study of biological inheritance patterns and variation.

• Gregor Mendel showed that traits are inherited as discrete units—was a monk who worked with pea plants b/c are easy to breed

• Many in Mendel’s day thought traits were blended.

6.3 Mendel and Heredity

Mendel’s data revealed patterns of inheritance.

• Mendel made three key choices in his experiments.– use of purebred plants– control over breeding– observation of seven

“either-or” traits that

appeared in two forms

(tall vs short, round vs

wrinkled)

6.3 Mendel and Heredity

Pea Plant characteristics:

• Pea shape• Pea color• Flower color• Pod shape• Pod color• Flower position• Plant height

6.3 Mendel and Heredity

• Cross = mating of two organisms• Mendel used pollen to fertilize selected pea plants.

Mendel controlled thefertilization of his pea plantsby removing the male parts,or stamens.

He then fertilized the femalepart, or pistil, with pollen froma different pea plant.

– Plants can self-pollinate and be pure-bred or can be cross-pollinated

– interrupted the self-pollination process by removing male flower parts

– P (parental) generation crossed to produce F1 (first filial) generation; F1 generation produces the F2 generation

6.3 Mendel and Heredity

• P generation: Mendel cross-pollinated the plants used purebred plants for the P generation (crossed pure white, pure purple)

• F1 generation, resulted in all plants that had purple flowers

• Mendel allowed the resulting plants to self-pollinate

• F2 generation, resulted in some plants had purple flowers and some had white

• What does this tell us??

6.3 Mendel and Heredity

• Results: for all 7 traits, Mendel found approximately ¾ of F2

offspring had one trait and ¼ had the other trait (3:1 ratio) when examining ONE trait at a time

6.3 Mendel and Heredity

• Conclusions:

– Traits are inherited as discrete units we now call genes

– Organisms inherit two copies of each gene, one from each parent.

– The two copies segregate

(separate) during gamete

formation. purple white

•Law of Segregation