The Origin of Genetics
Chapter 10- Section 1
Ag Biology
What is Heredity?
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The passing of traits from parents to offspring
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Traits: any heritable character that varies
among individuals (hair color, eye color, etc.)
Gregor Mendel
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Austrian Monk
Studied heredity by breeding different varieties
of Pisum sativum (garden pea)
First person to develop rules that accurately
predicted patterns in heredity
His studies formed the basis of genetics
He is called the “Father of Genetics”
T.A. Knight’s Contribution
to Study of Genetics
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British farmer
Crossed a variety of garden pea with purple
flowers with a variety with white flowers
Result: all offspring had purple flowers
Then, he crossed 2 purple offspring and their
offspring had both purple and white flowers
White trait reappeared in second generation
How did Mendel’s research differ
from Knight’s?
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Mendel took Knight’s experiment to the next
level.
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He counted the numbers of each kind of
offspring and analyzed the data
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This type of math analysis was on the cutting
edge of research at the time
Quiz Time!!!!!
1.
What did Mendel use to perform his genetic
experiments?
2. What did Mendel do with Knight’s
experiments?
3. When the P generation plants were bred,
purple with white, what did the offspring
look like?
4. When the F1 generation was bred what did
the offspring look like?
5. Out of 4 plants in the F2 generation, how
many were purple and how many were
white?
Why were garden peas used to
study heredity?
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Many traits that have two clearly different forms
(easy to tell apart)
They are self-fertilizing
Small
Mature quickly
Many offspring
Grows easily
The 7 traits studied by Mendel and
their contrasting forms:
Flower
Seed
Seed
Pod
Color
Color
Shape
Color
The 7 traits studied by Mendel and
their contrasting forms:
Pod
Flower
Plant
Shape
Position
Height
Monohybrid Cross
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A cross that involves one pair of contrasting
traits
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Examples: crossing a plant with purple flowers
with a plant with white flowers
Mendel’s Experimental Design
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Step 1: Mendel allowed each variety of garden
pea to self-pollinate for several generations.
(Ensured true-breeding)
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True-Breeding: displaying only one form of a
particular trait in offspring
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Served as the parental generation (P generation)
Mendel’s Experimental Design
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Step 2: Mendel cross-pollinated two P
generation plants with contrasting forms of a
trait. Offspring are F1 generation.
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Step 3: Mendel allowed the F1 generation to
self-pollinate. Offspring were called F2
generation.