SOLVING GENETIC
PROBLEMS
Oksana Hrycyk
John Miranda
Specific Expectations
D2.3
Use the Punnett square method to solve basic
genetics problems involving monohybrid crosses,
incomplete dominance, codominance, dihybrid
crosses, and sex-linked genes [PR, AI, C].
D3.3
Explain the concepts of genotype, phenotype,
dominance, incomplete dominance,
codominance, recessiveness, and sex linkage
according to Mendelian laws of inheritance.
Genetic problems? No problem
A man comes to a doctor and says “doctor, my wife
is cheating on me. She and I are both black, my son
however, is white…she must have done it with
somebody else”. “ Another patient says that his wife
is also cheating, they both have brown eyes but the
baby is blue-eyed”. The doctor sights, he knows
about dominant and recessive alleles. Do you know
what that is?
Blue eyes from brown eyes video
• http://www.youtube.com/watch?v=7QwTEKhVEDk
Most people think that we should look like
our parents, however, most of us usually
have different physical characteristics.
• It all start by knowing about dominant and recessive
alleles.
• To understand this, we need to learn about phenotype,
genotype, recessiveness, dominance, and how to use
Punnett squares to solve genetic problems.
Lesson
Sequence
• Lesson One: Genotype Vs.
Phenotype.
• Lesson Two: DNA and Alleles.
• Lesson Three: Recessiveness and
dominance.
• Lesson Four: Mendelian Laws.
• Lesson Five: monohybrid crosses,
dihybrid crosses, and sex-linked
genes.
• Lesson Six: Solving Genetic
problems with Punnett squares.
Alleles Gizmos Lab
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Log on: www.explorelearning.com
CLASS CODE: S56M7CTW34
Students will solve mouse genetic problems with 2 traits.
Students interactively learn that crossing parents with
certain dominant or recessive traits will produce a
probability of offspring.
• Students will understand the effects of dominant alleles
in each crossing.
Dominant and Recessive Alleles Role-Play
• There will be 2 groups of 12 students. Each student will
represent Alleles. Two from the mother, two from the
father (each parent will have dominant and recessive
genes of a physical characteristic. Each student will be
wearing different colour T-shirts for easy distinction), the
other eight students will be used to provide the 4
possible genotype combinations. A captain will be
selected for each group.
• Each group will provide the probabilities of each possible
combination in a certain amount of time.
Allele Role-Play Activity Continuation
• The group to get all 4 combinations in the shortest
amount of time will be the winner.
• Another 5 exercises will be performed; students will
select the parents’ genotype this time.
• The group that gets the 4 combinations the fastest in all
6 exercises will get a box of cookies (the winners will be
asked to share with the rest of the class to promote
sportsmanship).
Genetically Modified Food Debate
• Two groups of 5 students will be selected. One group
in favour, the other against the use of genetically
modified foods.
• Each group will have a week to prepare and find valid
research to support their case. A rubric will be used
to assess their knowledge, communication,
application, and technology.
• A body of 5 judges will conduct the debate, prepare
rules, and assess which group had a more
influencing approach. Judges will make a half
reflection on how debaters affected their decision.
• The audience will be the jury who will decide which
team was the winner. They will make a one-page
reflection on how debaters affected their decision.
Punnett Square Problems
• There will be various scenarios where students will solve
the genetic problem by using Punnett squares.
• Solutions to problems will be taken in class by using
PowerPoint and clickers. Students will have the chance
to chose their answers. Once answers are provided, a
short explanation will be added.
Potential Student Difficulties and Solutions
1. Mathematics involved with Punnett Squares, specifically
probabilities and binomial distributions.
•
Students will need to apply the Mendelian laws and determine
probabilities to make predictions on the genotypes and/or phenotypes of
the progeny. One method that may help overcome this difficulty is to spend
a period reviewing these math concepts, as well as working through
various applicable probability problems to clarify the methodology,
including tips and tricks. These problems do not have to be geneticsbased, but can be any typical probability problem, like rolling dice, drawing
playing cards etc.
Potential Student Difficulties and Solutions
2. Understanding the notions of alleles, loci and genes, as
they all can be conceived as somewhat similar.
An allele is the various alternate forms of a single gene, and that single
gene can have many alleles. A locus, on the other hand, is any specific
location on a chromosome. We think the suggested Alleles Gizmos Lab
and the Alleles Role Play may help clarify these differences as well as
clarify various other questions about alleles and genes that may arise.
Potential Student Difficulties and Solutions
3. Distinguishing between the Mendelian laws: the law of
segregation and the law of independent assortment.
These two laws are quite similar, but define different
ideas. The law of segregation states that two alleles of a
single trait segregate during gamete formation and then
one allele from each parent randomly unite at
fertilization, while the law of independent assortment
states that different pairs of alleles segregate
independently of each other.
•
The Alleles Gizmos Lab and the Alleles Role Play can be used along with
clear definitions and examples to help clarify any misunderstandings.
Safety Precautions
1. There is a virtual lab, so to avoid students accessing
inappropriate internet sites, the school library will block
any other website. The student will only have access to
www.explorelearning.com for the gizmos lab.
2. For the role-play activity, students will be taken to the
gym for ample space where they can easily and with
speed move to work on their Punnett square activities.
Practical Applications
• Practical applications of genetics in medicine and surgery.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1817215/pdf/brmedj02
576-0029.pdf
http://www.biophage.com/genetic-engineering.html
• Disease diagnosis and prevention through genetic technology:
http://www.michener.ca/ce/postdiploma/genetics_technology.php#w
hat
• Genetic Engineering in agriculture: Show students (after debate)
how genetically modified food has helped increase crop yield and
support the 7-billion world population. Foods with added minerals
and vitamins.
• Forensic medicine: Through the use of genetics, mysteries and
crimes can be solved.
Differentiated Assessment
• A diagnostic quiz will be administered testing student knowledge in
probability and probability problems.
• A Student Exploration Worksheet associated with the Alleles
Gizmos Lab, which will be marked for Knowledge and
Understanding, and Thinking and Inquiry (formative assessment).
• Rubric for the Allele Role Play activity and debate for knowledge
and understanding as well as communication and application.
• Quizzes assessing the progress of their understanding, including
definitions, Punnett squares and genetic problems.
• Oral responses during in class discussions.
• Unit test which true/false, multiple choice, matching exercises, math
problems, short answers, and a reflection section (essay).