Transcript Heredity - Matthew Donato

Heredity
Mendel and His Peas
Gregor Mendel
What Did Mendel Want to
learn?
 Was there a pattern to Heredity?
 Why did some traits skip a generation?
Why Pea Plants?
 Mendel had worked with pea plants
before.
 Pea plants grow quickly. Several
generations can be studied in a relatively
short period of time.
 Many varieties available.
 They are able to self pollinate.
Self Pollination
Cross Pollination
Cross Pollination
Self Pollinating Plants
 Self pollinating plants can produce true
breeding plants.
 A true breeding plant will always produce
offspring identical to itself.
 A true breeding plant with purple flowers
will always have offspring with purple
flowers.
What was he looking For?
 Mendel only studied one characteristic at
a time.
 A characteristic is a feature that has a
variety of forms.
 The varieties of the forms are called
traits.
Traits and characteristics
 The words traits and characteristics can
not be used interchangeably.
 A trait is more specific.
 Hair color is a characteristic, red hair is a
trait.
 Can you name a characteristic and a
trait?
What was he looking For?
 Mendel studies certain characteristics
such as plant height, seed shape, flower
color, pod color, etc…
 Remember he only studied one
characteristic at a time.
Mendel’s First Experiment
 He crossed a true breeding white
flowered plant with a true breeding purple
flowered plant.
 He removed the anthers from the flowers
so that they could not self pollinate.
Mendel’s First Experiment
Results of His first
Experiment
 All the first generation plants had purple
flowers.
 When he tested the other characteristics
he got the same results.
 One of the tested traits always showed
up, but the other did not.
Results of His first
Experiment
 Mendel called the trait that showed up in
the first generation the dominant trait.
 The trait that did not show up was called
the recessive trait.
Mendel’s Second
Experiment
 He self pollinated the first generation
plants
Results of His second
Experiment
 The white flowers showed up again.
 When ever he repeated the same
experiments he got the same results.
 The second generation plants had a
three to one ratio.
 For every three dominant traits that
showed up, one recessive was present.
Results of His second
Experiment