The 3rd lesson in a series of lessons on Mendelian genetics and heredity. This PP is meant to serve as a guide/framework for the lesson.

1. Mendellian Genetics & Heredity
Dihybrid Crosses

2. Today’s schedule:
 Warm-up
 Review of Punnett squares and monohybrid crosses
 Review of ratios and percentages
 Introduce dihybrid crosses
 Work collaboratively on dihybrid crosses
 Game: We are alleles

3. Common core
MSDE (2012):
INDICATOR
3.3.2 The student will illustrate and explain how expressed traits
are passed from parent to offspring.
Assessment limits:
 phenotypes (expression of inherited characteristics)
 dominant and recessive traits
 sex-linked traits (X-linked only; recessive phenotypes are more
often expressed in the male)
 genotypes (represented by heterozygous and homozygous pairs
of alleles)
 Punnett square (use to predict and/or interpret the results of a
genetic cross; translate genotypes into phenotypes - monohybrid
only)
 pedigree (use to interpret patterns of inheritance within a family)

4. Warm up
hint: use a Punnett square to solve
 Grey fur is dominant
 White fur is recessive
 Female is heterozygous for grey fur
 Male has white fur
 Determine the possible genotypes and phenotypes of
their offspring
 Express each genotype and phenotype as a ratio

5. objectives
 By the end of today’s lesson, students will be able
to discuss Mendelian genetics & heredity using
scientific vocabulary with 95% accuracy by
practicing it in small groups.
 By the end of today’s lesson students will know
how to express the outcome of crosses as ratios
and percentages with 85% accuracy.
 By the end of today’s lesson students will
understand how to create and use a Punnett
square for dihybrid crosses with 80% accuracy.

6. try this….
 Grey fur is dominant; white fur is recessive
 Red eyes are dominant; black eyes are recessive
 Female is heterozygous for grey fur and has
black eyes
 Male has white fur and is homozygous dominant
for red eyes.
 Determine the possible genotypes and
phenotypes of their offspring.

7. picture it…
 Grey fur is dominant; white
fur is recessive
 Red eyes are dominant;
black eyes are recessive
 Female is heterozygous for
grey fur and has black eyes
 Male has white fur and is
homozygous dominant for
red eyes.
 Determine the possible
genotypes and phenotypes
of their offspring.

8. Classwork
 Please work with your seat-mates to complete the
worksheet:
 http://betterlesson.com/document/78673/bikini-
bottom-dihybrid-practice?from=search

10. Talk with your mates
What do you
think…..?

11. homework…a review
Complete this review on line:
http://www.athro.com/evo/gen/punexam.html
After you complete the review, please fill this in
(found in your handout package):
On this page you have given _____answers of
which ______were right. *
*this information is provided to you after you
complete the review

12. Exit ticket: what do we need to talk
more about?
 Meiosis/Mitosis
 Gene sorting
 Vocabulary
 Offspring Ratios
 Punnett squares
 Monohybrid crosses
 Dihybrid crosses

13. References
 McDonald, L. (2010, September 09). Bikini
bottom dihybrid practice. Retrieved from
www.betterlesson.com
 NOVA (2012) Excerpt from NOVA: Cracking Your
Genetic Code [Video]. Retreived from
http://www.teachersdomain.org/asset/cygc12_vid
_cancergene/