The History Of

Genetics: Gregor Mendel and his

Peas

The results of Mendel’s studies were so important that he is considered:

Father of Genetics

•Genetic first started when an Austrian monk, named Gregor Mendel, performed a series of experiments on garden peas.

•Mendel observed qualitative information about the traits of the pea plants. He then tried to quantify how those traits were passed from one generation to another.

•Mendel developed purebred lines of pea plants. He recorded the results of his experiments and made statistical notes about how the traits were passed down.

WHY PEAS?• Structure of the pea flowers • Presence of distinctive traits • Rapid reproduction cycle • Grow quickly • Produce large number of

offspring• Cheap and easy to grow and

maintain• Pea plants normally self-

pollinate but can cross-pollinate if the anthers (the boy parts) are removed when the flower is young

stigma

style

Ovary (holds female gametes-eggs)

Anther-holds male gametes

filament

petal

sepal

Self Pollination

• Self-pollination female and male gametes (egg & pollen) from the same plant form a zygote

example: this is how plants normally go about their business

Purple Flower

Anther (boy part)

Stigma (g

irl part)

pollen

*

Pollen (gamete from the boy part) goes to the stigma ( the girl part) of the same flower fertilizes the female gamete

Petals form a tent over the stigma and anthersPollen is trapped inside

Cross-pollination• Cross-pollination

female and male gametes from two different plants form a zygote

example: Mendel “painted” pollen from one plant onto the stigma of another plant, or insects transfer pollen from one plant to another

Mendel painted pollen from another plant onto the stigma of the flower

Mendel cut off the anthers so the plant does not produce its own pollen.

Mendel studied characteristics in the parents and offspring of pea plants. The plants displayed several easily-observed characters in one of two contrasting traits or forms

Trait or Characteristic(coded for by a gene) Alleles or Forms of the Trait

Seed color yellow and green

Seed shape wrinkled and smooth

Flower color purple and white

Pod color yellow and green

yellow

green

ATGCCAGCTACC

CTGACCGTACCG

Different sequences

Mendel studied characteristics in the parents and offspring of pea plants. The plants displayed several easily-observed characters in one of two contrasting traits or forms

Mendel observed that there were two different types of pea plants

Purebred Plants

• plants that, when self-pollinated, produce the same form of a trait in all offspring

• Example: white flower plants that produce offspring with white flowers

Hybrid Plants

• plants that, when self pollinated, produce more than one form of a trait in their offspring

• Example: Purple flower plants that produce some purple and some white flowered offspring

• Mendel performed his experiments with great patience and precision. He kept careful records. Mendel’s work spanned 10 years and involved over 280 genetic crosses producing some 28,000 pea plants.

• Mendel was trained in mathematics and used his background in probability to analyze the results of his crosses.

Describe (briefly) the experiments that Gregor Mendel set up.

• Mendel set up crosses with pea plants to see how their traits were passed down from generation to generation

Why were pea plants an ideal choice for Mendel’s experiments? (give at

least three reasons)• Structure of the pea flowers • Presence of distinctive traits • Rapid reproduction cycle • Grow quickly • Produce large number of offspring• Cheap and easy to grow and maintain• Pea plants normally self-pollinate but can cross-

pollinate too

What were some the traits he observed? What were the different alleles for these traits?

Traits Dominant Allele Recessive Allele

Flower color Purple White

Seed Color Yellow Green

Pod Color Green Yellow

Pod Shape Full Constricted

Seed Shape Round Wrinkled

Flower Position Axial Terminal

Plant Height Tall Short