Gregor Mendel studied inheritance through pea plant experiments in the mid-1800s. He found that alleles (versions of genes) show up in predictable patterns, with some alleles being dominant over others. Mendel also discovered that alleles segregate and assort independently during reproduction, laying the foundations for modern genetics.

1. Genetics Unit
• On one page of your notebook, create a
vocabulary sheet. Throughout these
notes, write any red vocabulary words
and their definitions on this page.
Vocabulary Word Definition:
1.
2.

2. Gregor Mendel
• Austrian Monk
• Studied pea plants

3. Mendel’s Crossbreeding
Trait Dominant Recessive
Allele Allele
Seed Shape Round Wrinkled
Seed Color Yellow Green
Seed Coat Gray White
Color
Pod Shape Smooth Constricted
Pod Color Green Yellow
Flower Axial Terminal
Position
Plant Height Tall Short

4. Trait Dominant Recessive
Allele Allele

5. Inheritance
Gregor Mendel – “Father of Genetics”
• Experimented with pea plants in 1850’s to
show basic patterns of inheritance
 Seed Shape (round or wrinkled)
 Seed Color (yellow or green)
 Seed Coat color (gray or white)
 Pod Shape (smooth or constricted)
 Pod Color (green or yellow)
 Flower Position (axial or terminal)
 Plant Height (tall or short)
Traits Alleles

6. Inheritance
Gregor Mendel – “Father of Genetics”
• Did experiments with pea plants in mid-late
1800’s to show basic patterns of inheritance
 Seed Shape (round or wrinkled)
 Seed Color (yellow or green)
 Seed Coat color (gray or white)
 Pod Shape (smooth or constricted) Found that when two plants
 Pod Color (green or yellow) with different alleles are
 Flower Position (axial or terminal) crossed, the offspring look
 Plant Height (tall or short)
like one of the parents, rather
than a blending of both
parents.
Dominant Recessive Principle of Dominance
Alleles Alleles Some alleles are dominant
and others are recessive

7. Inheritance
Gregor Mendel – “Father of Genetics”
• Did experiments with pea plants in mid-late
1800’s to show basic patterns of inheritance
 Seed Shape (round or wrinkled)
 Seed Color (yellow or green)
 Seed Coat color (gray or white)
 Pod Shape (smooth or constricted) Found that when two plants
 Pod Color (green or yellow) with different alleles are
 Flower Position (axial or terminal) crossed, the offspring look
 Plant Height (tall or short)
like one of the parents, rather
than a blending of both
Traits Alleles parents.
Dominant Recessive Principle of Dominance
Alleles Alleles Some alleles are dominant
and others are recessive

8. Inheritance: the passing of traits
from parents to offspring
Gregor Mendel – “Father of Genetics”
• Phenotype - The observable physical characteristic of a trait
• Genotype - The genetic combination of alleles for a trait
• Punnett Square – tool used to predict probability of phenotype
Phenotype: White
Genotype: pp
Phenotype: Purple
Genotype: PP Notice that letters are used to represent the
alleles (usually correspond to the dominant
phenotype – e.g. “P” for purple)
Upper Case Letters = Dominant Allele
Lower Case Letters = Recessive Allele

9. Practice
• Overview of genes to traits video
• Copy the 3 questions below:
• What do they mean when the say “you
have your father’s hair”?
• How many chromosomes do organisms
have?
• How much DNA do we have in common
with other animals?

10. • Complete the Phenotype Survey and
write the results in your notebook.

11. Inheritance
Gregor Mendel – “Father of Genetics”
• Found that alleles show up in predictable patterns and
that some alleles show up more often than others
• Homozygous (Pure-Breeds) - both alleles are the same
• Heterozygous (Hybrids) - both alleles are different
• Carriers – heterozygotes for a recessive trait
Pure-Breed Crosses result in: Hybrid Crosses result in:
100% chance dominant phenotype 75% chance dominant phenotype
25% chance recessive phenotype

12. Inheritance
Gregor Mendel – “Father of Genetics”
• Found that alleles show up in predictable patterns and
that some alleles show up more often than others
• Alleles can be tracked through multiple generations
and probabilities determined
Parents: P1
generation
First Generation: First Filial (F1)
100% chance dominant phenotype
Second Generation: Second Filial
(F2)
75% chance dominant phenotype
Third Generation: Third Filial (F3)
63% chance dominant phenotype
100% chance 75% chance 75% chance 0% chance

13. Practice
• Video on making punnett squares
• In your notebook complete the
Probability (Long vs Short Big Toe) Lab.

14. Summary of Mendel’s Principles
Gregor Mendel’s work forms the basis of modern genetics:
• Genes are passed from parent to offspring
• Some forms of genes (alleles) are dominant while others are recessive
• Genes randomly segregate (independent assortment) when gametes are formed
• The alleles for different genes usually segregate independently of one another
Linked genes (genes that occur very close
to one another on a chromosome) are the
exception
Write these 4 ideas
from Mendel in your
notebook