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LESSON TITLE: Mendel’s Pea Plants, Punnett Squares
TIME REQUIRED: 75 min
SUBJECT / STRAND: SBI 3U, Genetic Continuity
GRADE: 11U
EXPECTATIONS COVERED:
ASSESSMENT:
Overall Expectation:
- demonstrate an understanding of the necessity of meiosis and describe
the importance of genes in transmitting hereditary characteristics
according to Mendel’s model of inheritance
Specific Expectations:
- predict the outcome of various genetic crosses
- describe and explain the process of discovery (e.g., the sequence of
studies and the knowledge gained) that led Mendel to formulate his laws
of heredity
Formative
BACKGROUND KNOWLEDGE:
SAFETY CONCERNS?
- genetics terms: Genetics, trait, genes, phenotype, P generation, F1
generation, F2 generation, dominant allele, recessive allele,
incomplete dominance, pure-bred, true-breeding, hybrid, Law of
segregation, Law of independent assortment
- formulating and interpreting basic ratios
- minimal plant anatomy
None
LESSON DESCRIPTION:
- (15 min) Complete Human Trait activity
o determine ratios and percentages of dominant/recessive traits for entire class
- (20 min) Introduction to Mendel and his Pea Plants
o brief history of Mendel
o pea plants
 why they were used (7 characteristics, life span)
 abbreviated anatomy of a flower, methods of fertilization
- (30 min) Introduction to Single Trait Inheritance – Punnett Squares
o work through practice problems – page 135-137, #1, 2, 3
- (10 min) Independent work on problems
o Bikini Bottom worksheet
o page 138, #3, 4
o extra practice – page 139
 Section 4.1 - 4.2, #3ab, 4
REFLECTION:
SBI 3U - Genetics
Mendel and his Pea Plants
Gregor Mendel (1822-1884) was
an Austrian monk whose experiments
with garden peas laid the foundation
for the science of genetics.
Mendel’s work not only explained the
mechanism of gene inheritance in
plants, but also provided a basis
for understanding heredity in
general.
The charts provided show the
seven different characteristics of
garden pea plants that Mendel
studied, as well as the alleles and
possible genotypes. Keep in mind
that plants with white flowers
produce seeds that are yellow, and
plants with violet-purple flowers
produce seeds that are green.
Trait
Alleles
(DOMINANT/
recessive)
Possible
genotypes
Seed shape
ROUND
wrinkled
RR or Rr
rr
Seed colour
YELLOW
green
YY or Yy
yy
Pod shape
INFLATED
constricted
II or Ii
ii
Pod colour
GREEN
yellow
GG or Gg
gg
Flower
colour
PURPLE
white
PP or Pp
pp
Flower
position
on stem
AXIAL
(side of
stem)
top
AA or Aa
aa
Plant
height
(stem
length)
TALL
dwarf
TT or Tt
tt
Practice Problems
Page 138, #3 & #4
3. For each of the
the table on the
information:
- parent
- parent
- parent
following situations, create a Punnett square using
front of the page, and determine the following
phenotype
genotype
gametes
- F1 generation genotypes
- F1 generation phenotypes
a)
b)
c)
d)
Two heterozygous tall parents are crossed.
A heterozygous tall plan is crossed with a dwarf plant.
Two plants that are heterozygous for purple flowers are crossed.
A plant that is homozygous for green pods is crossed with a plant
that has yellow pods.
e) A plant that is homozygous for round seeds is crossed with a plant
that is heterozygous for round seeds.
4. In guinea pigs, the allele for a black coat is dominant over the
allele for a white coat. A black guinea pig was crossed with a white
guinea pig. All F1 offspring have black coats.
a) Describe how you can determine whether or not the black parent is
homozygous or heterozygous for the condition. Indicate the letter
you will use to represent an allele.
b) If 10 offspring were produced, indicate how many you would expect
to have black coat colour, if the black parent were heterozygous.
SBI 3U – Genetics
___________________________
Name
Bikini Bottom Genetics
Scientists at Bikini Bottoms have been investigating the genetic makeup of the
organisms in this community. Use the information provided and your knowledge
of genetics to answer each question.
1. For each genotype below, indicate whether it is a heterozygous (He) OR
homozygous (Ho).
TT _____ Bb _____ DD _____ Ff _____ tt _____ dd _____
Dd _____ ff _____ Tt _____ bb _____ BB _____ FF _____
Which of the genotypes in #1 would be considered purebred?
________________________
Which of the genotypes in #1 would be hybrids?
_________________________________
2. Determine the phenotype for each genotype using the information provided
about SpongeBob.
Yellow body color is dominant to blue.
YY _________________ Yy _________________ yy _________________
Square shape is dominant to round.
SS _________________ Ss _________________ ss _________________
3. For each phenotype, give the genotypes that are possible for Patrick.
A tall head (T) is dominant to short (t).
Tall = _______________________ Short = _________________________
Pink body color (P) is dominant to yellow (p).
Pink body = ___________________ Yellow body = _____________________
4. SpongeBob SquarePants recently met SpongeSusie Roundpants at a dance.
SpongeBob is heterozygous for his square shape, but SpongeSusie is round.
Create a Punnett square to show the possibilities that would result if
SpongeBob and SpongeSusie had children. HINT: Read question #2!
A. List the possible genotypes and phenotypes for their
children.
B. What are the chances of a child with a square shape?
______ out of _____ or ______%
C. What are the chances of a child with a round shape?
______ out of _____ or ______%
5. Patrick met Patti at the dance. Both of them are heterozygous for their
pink body color, which is dominant over a yellow body color. Create a
Punnett square to show the possibilities that would result if Patrick and
Patti had children. HINT: Read question #3!
A. List the possible genotypes and phenotypes for their
children.
B. What are the chances of a child with a pink body?
______ out of ______ or ______%
C. What are the chances of a child with a yellow body?
______ out of ______ or ______%
6. Everyone in Squidward’s family has light blue skin, which is the dominant
trait for body color in his hometown of Squid Valley. His family brags that
they are a “purebred” line. He recently married a nice girl who has light
green skin, which is a recessive trait. Create a Punnett square to show the
possibilities that would result if Squidward and his new bride had children.
Use B to represent the dominant gene and b to represent the recessive gene.
A. List the possible genotypes and phenotypes for their
children.
B. What are the chances of a child with light blue skin?
______%
C. What are the chances of a child with light green skin?
______%
D. Would Squidward’s children still be considered
purebreds? Explain!
7. Mr. Krabbs and his wife recently had a Lil’ Krabby, but it has not been a
happy occasion for them. Mrs. Krabbs has been upset since she first saw her
new baby who had short eyeballs. She claims that the hospital made a mistake
and mixed up her baby with someone else’s baby. Mr. Krabbs is homozygous for
his tall eyeballs, while his wife is heterozygous for her tall eyeballs.
Some members of her family have short eyes, which is the recessive trait.
Create a Punnett square using T for the dominant gene and t for the
recessive one.
A. List the possible genotypes and phenotypes for
their children.
B. Did the hospital make a mistake? Explain your answer.