How are traits passed
down from one
generation to the
next?
LAB: Analyzing Inheritance in Fast Plants
Why do these plants grow
faster than other plants?
What will our seeds look like
when they grow?
Fast Plant Development Time Lapse
How did the parent-plants
create the next generation?
Pollinating and Harvesting Fast Plants
Wisconsin Fast Plants
Non-Purple
Stem
Purple Stem
The seeds from the
pollinated Non-Purple
Plants are used to
grow the F1
Generation
Seeds
Grow
into F1
Parent 1
Seeds (P1)
Parent Generation (P1)
NON-PURPLE
X
The seeds from the
pollinated F1 Plants are
used to grow the F2
Generation
POLLINATION
First Generation F1
Seeds
Grow
into F2
Second Generation F2
POLLINATION
Fast Plant
Generations
Parent 2
Seeds (P2)
Parent Generation (P2)
PURPLE
PLANTING PROCEDURES
① Measure 2 cm from the
bottom of each filter
paper and draw a line.
② Write the name of the
generation (P1 , P2 , F1 ,
F2) and the names of
your table/class.
Generation
Name
Table Name
Class Name
2 cm
PLANTING PROCEDURES
③ Put the filter paper inside the petri
dishes.
④ Fill the pipet with water;
slowly moisten the filter
paper with drops of H2O.
⑤ Send 1 person to Ms. B
collect the seeds for
each generation.
Generation
Name
Table Name
Class Name
2 cm
PLANTING PROCEDURES
⑥ Evenly spread out the seeds on the
filter paper. Place them ABOVE the
line.
⑦ Wait for 1 minute then
cover the petri dishes.
⑧ Bring the petri dishes to
Ms. B to place under the
lamp.
Generation
Name
Table Name
Class Name
2 cm
Results: P Generation
Results: F1 Generation
Results: F2 Generation
The
A, B, Peas…
of Life!!
How the study of pea
plants changed the way
we think about life.
(Genetics Week 1)
I Can #10
I CAN describe the results of Mendel's
crosses and explain the significance of
Mendel's findings for modern genetics.
Have you ever wondered why some
family members look very similar while
others look very different?
These are pictures of Peter, Lois, and
Chris from Family Guy.
SON (offspring):
Chris
DAD: Peter
MOM: Lois
Which character traits does Chris have in
common with his Dad or his Mom?
Heredity and Traits
• Traits are different
Detached Earlobe
forms of a
characteristic.
• Heredity is the
passing of traits
from parent to
offspring (children).
Attached Earlobe
More on Heredity…
• Only certain traits can be passed from parent to
offspring…
• For example, you might inherit your Dad’s hair
color but you wouldn’t inherit the scar on his chin
leftover from a painful football practice…
Purebred
• A true-breeding or a
purebred organism is
the offspring of many
generations that have
the same
characteristics.
• For example, purebred
purple pea plants
always come from
purple parent plants.
Gregor Mendel and Genetics
• Gregor Mendel (a
19th century monk),
was the first person
to study genetics
(the scientific study
of heredity).
Mendel’s Question
• Why are pea plant’s traits sometimes
similar to their parents and
sometimes very different?
Mendel’s Hypothesis
• Mendel hypothesized
that something was being
passed from parent to
offspring to control the
passing of traits--but
how? And was there a
pattern?
Hmmm…the passing
of traits must be
controlled by
something…right?
Mendel’s Experiment
• Mendel decided to “cross” two plants with
different traits to see what traits the
offspring would have.
• In his first experiment he “crossed” a tall
plant with a short plant.
Mendel’s Experiment
• Mendel called this first
generation of parent plants
the parental generation or
P generation
• The tall and short pea
plants he used were both
purebred.
• Mendel used a paint brush
to “cross-pollinate” the
two plants.
?
Mendel’s Data
• In the second generation
of pea plants, Mendel
saw that all of the
offspring were tall.
• He decided to cross this
second generation
(called F1 Generation)
with each other to see
what would happen.
?
Mendel’s Data
• But the next generation
(F2 Generation) was more
surprising!
• He had all tall plants
except for one small
plant!
WAIT! So 2 tall
plants produced
a SHORT plant?!
Mendel Experiments Again
(and again….)
• Mendel was so
confused by the
sudden reappearance of the
“short” trait, that
he decided to do
more experiments
like this one but
with different
traits.
Mendel’s Next Experiment
Violet
vs.
White
Mendel’s Data
• In all of Mendel’s crosses, only one
form of the trait showed in the F1
Generation.
• However, in the F2 Generation, the
“lost” form of the trait always
appeared in 1/4 of the plants.
Mendel’s Conclusions
• The “factors” that control each trait exist in
pairs. The female parent contributes one
factor, while the male parent contributes
another factor.
• One factor in a pair can “hide” the other
factor. (The “tall factor” hides the “short
factor”.
Summarizing Mendel’s
Experiments
 Mendel wanted to know
how it was possible for a
trait like white pea plant
color to disappear in one
generation and then
reappear in the next.
 His conclusion: the trait
is always there--its just
hidden by another trait!!
Dominant and Recessive Alleles
 Mendel came up
with the terms
DOMINANT and
RECESSIVE alleles
to describe how
some traits could
be “hidden” or
“masked” by other
traits.