the history of genetics: gregor mendel and his peas
TRANSCRIPT
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