Download Gregor Mendel 1822-1884

Gregor Mendel
1822-1884
Father of Genetics: Principles of biological
and hereditary traits
Austrian monk
Studied the
inheritance of
traits in pea plants
Developed the
laws of inheritance
Mendel's work
was not recognized
until the turn of
the 20th century
Gregor Johann Mendel
Between 1856 and 1863, Mendel cultivated and tested
thousands of pea plants
He found that the plants' offspring retained traits of the
parents
Gregor J. Mendel
• Heredity- the passing of traits from parent to offspring.
• Self-pollinate- A plant is often able to pollinate by itself
because it contains both the male and female
reproductive structures. This only requires 1 parent.
• Dominant trait- the trait observed when at least one
dominant allele for a characteristic is inherited
• Recessive trait- a trait that is apparent only when two
recessive alleles for the same characteristic are inherited
• Genes- a segment of DNA that carries hereditary
instructions and is passed from parent to offspring
• Alleles- multiple forms of the same gene
• Genotype- an organisms inherited combination of alleles
• Phenotype- an organisms inherited appearance
Vocab To Keep in mind
Mendel stated that physical traits are inherited as “particles”
Mendel did not know that the “particles” were actually
Chromosomes & DNA
Chromosome: a threadlike structure of nucleic
acids and protein found in the nucleus of most
living cells, carrying genetic information in the
form of genes.
Gene: a unit of heredity that is transferred
from a parent to offspring and is held to
determine some characteristic of the offspring.
Inheritance
Can be grown in a small area
Produce lots of offspring
Produce pure plants when allowed to selfpollinate several generations
Can be artificially cross-pollinated
Why grow peas?
• Mendel tested 7 traits:
1.
2.
3.
4.
5.
6.
7.
Flower color
Flower position
Seed color
Seed shape
Pod shape
Pod color
Plant height
Mendel’s tests
• Mendel crossed flowers that were true-breeding for each
characteristic.
• He crossed a purple (PP) flowered plant with a white (pp)
flowered plant. (Parent Generation)
The Peas
• The first generation (F1) of plants all had purple flowers.
Purple Parent (Pp)
The Peas cont’d
Purple Parent (Pp)
• Where did the white color go??
(Pp)
(Pp)
(Pp.)
(Pp)
• Mendel took two of his first generation (F1 x F1) purple
flowered plants and crossed them together.
The Peas cont’d
Purple Parent (Pp)
• In the second generation (F2) he had 3 purple flowered
plants, and 1 white flowered plant.
Purple Parent (Pp)
(PP)
(Pp)
(Pp)
(pp)
• Mendel noticed in the first generation, all of the white
flowers seemed to disappear.
• He called this a recessive trait.
• The white color faded into the background at first.
• It showed up in the next generation when he pollinated
the flowers.
Mendel & The Peas
• The color (purple) that seemed to mask over the
recessive color was named the dominant trait.
Mendel & The Peas
• Mendel was responsible for figuring out
that each plant carried two sets of
instructions for each characteristic (one
from the “mom” and one from the
“dad”).
• Trait- a distinguishing quality or
characteristic, typically one belonging to
a person
Traits
• 1. If you crossed a true-breeding black rabbit with a
true-breeding white rabbit, all of the offspring would be
black. Which trait is dominant in rabbits: black fur or
white fur?
• Which trait is recessive?
Test your knowledge
White Rabbit (bb)
• The trait
for black
fur is
dominant
over the
trait for
white fur.
The white
fur trait is
recessive.
Black Rabbit (BB)
(Bb)
(Bb)
(Bb)
(Bb)
And the answer is….
• Heredity- the passing of traits from parent to
offspring.
• Self-pollinate- A plant is often able to pollinate by
itself because it contains both the male and female
reproductive structures. This only requires 1 parent.
• Dominant trait- the trait observed when at least one
dominant allele for a characteristic is inherited
• Recessive trait- a trait that is apparent only when
two recessive alleles for the same characteristic are
inherited
• Genes- a segment of DNA that carries hereditary
instructions and is passed from parent to offspring
• Alleles- multiple forms of the same gene
• Genotype- an organisms inherited combination of
alleles
• Phenotype- an organisms inherited appearance
Any last questions???