1 Review What did Mendel conclude determines
inheritance
Explain What are dominant and recessive alleles
Apply Concepts Why were true breeding pea plants
important for Mendel’s experiments
2 Review What is segregation
Explain What happens to alleles between the P
generation and the F2 generation
CH 11 INTRODUCTION TO GENETICS
11.1 The Work of Gregor Mendel

Heredity
 Delivery

of characteristics from parent to offspring
Genetics
 Scientific
study of heredity.
The Experiments of Gregor Mendel



Founded modern science of
genetics
Austrian monk
Charge of the monastery
garden.
The Experiments of Gregor Mendel

Worked with pea plants
 Multiple
generations each
growing season
 Many traits
 Traits in one of two forms
 Easy to grow
 Lots of offspring.
The Role of Fertilization

Stamen
 Male
part of each flower makes pollen (contains
sperm)

Carpel
 Female
portion of each flower produces reproductive
cells called eggs.
Fertilization



Male and female reproductive cells join
For peas tiny embryo encased within a seed
Peas normally are self pollinating
 Sperm
and egg are from same parent.

Trait
 Specific
characteristic of an individual, such as seed
color or plant height
 May vary from one individual to another

True-breeding or Pure Breeding
 Produce
offspring with identical traits to themselves.

He cut away the pollen-bearing male parts and
then dusted on the pollen from a different flower.

Hybrid
 Offspring
traits.
of crosses between parents with different

Generations
 P1-
original parents
 F1- first offspring, F is for filial
 F2- second generation of offspring; F1’s kids.
Mendel’s Two Conclusions
Individual’s characteristics are determined by
factors that are passed from one parental
generation to the next
1.
•
These factors come in two varieties
Principle of dominance
2.
•
Some alleles are dominant and will cover up the
recessive version of the allele.

Genes
 Factors

that are passed from parent to offspring
Alleles
 Different
forms of the gene.

Dominant
 Version
of trait that shows up in each generation of
Mendel’s experiments
 Can hide the other form of that trait
 Capital letter

Recessive
 Version
that was covered up in the F1 generation
 Lower case letter.

Tall plant is dominant over short.
Where Did the Recessive Gene Go


Mendel allowed all
seven kinds of F1
hybrids to self-pollinate
He found recessive trait
in about ¼ of the F2
generation.

Segregation
 Alleles

split and each gamete only carries one
Gamete
 Sex
cells (egg or sperm).

Dominant allele had masked the corresponding
recessive allele in the F1 generation.

F1 plants were tall with a tall
allele from one parent and a
short allele from the other
parent.

F1 adults produces
gametes, the alleles for
each gene segregate
from one another.


Whenever two t’s
combine, a short plant
results
Whenever there is even
one T, a tall plant
results.