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Heredity. Ronak Ahmed Duhok International School 2012-2013. Chapter 1 / Section 1. Mandel and the Pea Plants. What is the meaning of Heredity?. The passing of genetic traits from parent to offspring. straight hair. Curly hair. Black eyes. Brown eyes. Gregor Mendel.

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Ronak Ahmed

Duhok International School


Chapter 1 section 1
Chapter 1 / Section 1

Mandel and the Pea Plants

What is the meaning of heredity
What is the meaning of Heredity?

The passing of genetic traits from parent to offspring.

straight hair

Curly hair

Black eyes

Brown eyes

Gregor mendel
Gregor Mendel

Born in 1822 in Heinzendorf, Austria.

when he was 21st Years old, he was sent to Vienna for receiving training in teaching.

He discovered the principles of heredity when he did his research on pea plant.

Unraveling the mystery
Unraveling the Mystery

During his working with plants, he knew that the patterns of inheritance were not always clear.

Why pea
Why Pea?

Grow Quickly.

Many different kinds available.

Able to self- pollinate.

What is the self pollinate?

A self-pollinating plants has both male & female reproductive structures. So, pollen from one flower can fertilize the ovule of the same flower or the ovule of another flower on the same plant.

Because eggs (in an ovule) and sperm (in pollen) from the same plant combine to make a new plant, Mendel was able to grow true-breeding plants.

Why is it important that pea plants can self-pollinate?

What is the result of true breeding plant self pollinating

What is the result of true-breeding plant self-pollinating?

All of its offspring will have the same trait as the parent.

How cross pollinating occur
How cross-pollinating occur?

Pollen from one plant fertilizes the ovule of a flower on a different plant

The carrying of pollen is done by several ways:

1- By insect

2- By wind

3- By water

Mendel studied only one characteristics at a time
Mendel studied only one characteristics at a time

Characteristic : is a feature that has different forms in a population.

  • Mendel used plants that had different traits for each of the characteristics he studied.

What did mendel did to be sure that the plant cross pollinated
What did Mendel did to be sure that the plant cross-pollinated?

  • He removed the anther of one plant so that the plant could not self-pollinate.

    2. He used pollen from another plant to fertilize the plant.

    This step allowed Mendel to select which plants would be crossed to produce offspring.

Mendel s experiments
Mendel’s Experiments cross-pollinated?

  • In his first experiments, Mendel crossed pea plants to study seven different characteristics.

  • The offspring from such a cross are called first-generation plants. All have purple flowers.

  • Mendel called the traits that appeared in the first-generation plants as dominant trait, while the other trait that seemed to fade into the background as a recessive trait.


  • Dominant trait: cross-pollinated?The trait observed in the first generation when parents that have different traits are bred.

  • Recessive trait: a trait that reappears in the second generation after disappearing in the first generation when parents with different traits are bred.


  • In his second experiments, he allowed the cross-pollinated?first generation plants, which resulted from his first set of experiments, to self pollinate.

  • Mendel did this same experiment on each of the seven characteristics. In each case, some of the second-generation plants had the recessive trait.

The recessive trait for white flowers is reappeared

Ratios in mendel s experiments
Ratios in Mendel’s Experiments cross-pollinated?

  • Mendel compared the number of purple to white flowers by counting them and for all traits in the second generation.

  • A ratio: is a relationship between two different numbers that is often expressed as a fraction.

  • The recessive trait did not show up as often as the dominant trait. He decided to figure out the ratio of dominant traits to recessive traits.

Gregor mendel gone but not forgotten
Gregor cross-pollinated? Mendel gone but not forgotten

  • Mendel realized that his result could be explained only if each plant had two sets of instructions for each characteristics. Each parent would then donate one set of instructions.

  • In 1865 Mendel published his findings.

  • After 30 years of his deaths, his work was widely recognized.