EXPERIMENT 8: Phenotype and Genotype

expo_8 discussion_questions
 

EXPERIMENT 8: Phenotype and Genotype

 

Read the entire experiment and organize time, materials, and work space before beginning.

Remember to review the safety sections and wear goggles when working with chemicals.

Allow 40 to 60 minutes for this experiment

Objectives: To understand phenotype and genotype, and

To understand why you have certain characteristics

Materials: Student Provides: Self

Mirror

From LabPaq: PTC taste paper

Discussion and Review: Who you are is a product of both your physical nature and

your nurturing or training. Genetics is the study of your nature. By looking at some of

your physical features you can understand some of your genetics and why you have

certain physical features.

The study of genetics is one of the hottest areas of study in biology today. The recent

completion of the genome project, combined with growing interest in cloning and gene

replacement therapy, has generated great interest in genetics. In biology, genetics can

be divided into classical genetics (heredity) and molecular genetics. Heredity is

generally thought of as a study of parents and offspring and how their traits or

characteristics are related.

Two organisms can look alike but have different underlying gene combinations. The

way an organism looks and behaves is called its phenotype. The combination of genes

or alleles an organism contains for a particular trait is called its genotype. You cannot

always know an organism’s genotype simply by its appearance.

Mendel’s law of segregation explains the results of crosses between parents with similar

characteristics or phenotypes but whose offspring may have different characteristics.

He concluded that the two alleles for each trait must separate when gametes are

formed, and that a parent passes on at random only one allele for each trait to each

offspring. Each offspring therefore has two alleles, but one will dominate and determine

the phenotype. An organism is homozygous if its two alleles for a trait are identical, and

it is heterozygous for a trait if its two alleles for the trait differ from each other.

In this experiment, you will look at several human traits in order to observe Mendel’s law

of segregation. These traits are controlled by a single gene with two alleles and each

allele, if it is dominant in the pair, produces a distinct phenotype.

Hands-On Labs SM-1 Lab Manual

71

PROCEDURES: For each of the following traits determine your phenotype and if

possible your genotype. If you have a dominant phenotype, you may have either a

recessive allele and a dominant allele or two dominant alleles, whereas if your

phenotype is recessive, your genotype is recessive homozygous. Record your

observations in a table.

1. Dimpled chin: A cleft in the chin is a dominant trait.

2. Free ear lobe: For ear lobes to hang free is dependent on

a dominant allele. If two recessive alleles are present the

ear lobes are directly attached to the head.

3. Ability to taste PTC: Some people have the dominant gene that

allows them to detect the bitter taste of PTC while others do not. Put

a piece of PTC impregnated paper on your tongue for about five seconds. If you are

a taster you will know it.

4. Interlocking fingers: When the fingers are interlocked, some

people place the right thumb on top of the left (dominant allele);

others place the left thumb over the right (recessive allele).

5. Mid-digital hair: Some people have hair on the second (middle) joint of one or more

of the fingers, while others do not. The presence of hair is due to a

dominant allele and the absence of hair from all fingers is due to a

recessive allele.

6. Bent little finger: A dominant allele causes the last joint of the little

finger to bend inward toward the fourth finger.

7. Widow’s peak: The dominant allele produces a hairline with a point

in the center of the forehead (widow’s peak). The recessive allele

gives a continuous hairline.

8. Hitchhiker’s thumb: When you can bend the tip of the

thumb back 90 degrees in relation to the rest of the thumb

you are homozygous recessive for this allele.

9. Pigmented irises: When there is no pigment in the front part of the eyes and a blue

layer at the back of the iris shows through you are homozygous for the recessive

allele allowing blue eyes.

10. Long palmar muscle: Clench your fists tightly and examine the tendons running

over the inside of the wrists. If there are three tendons you have the recessive

alleles for the long palmar muscle, if there are only two tendons you do not.

Exercise: Refer to the previous experiment and construct a Punnett square showing

both the genotype and phenotype ratios possible if two heterozygous brown-eyed

individuals with dimpled chins were to have children. Your Punnett square will be 4 x 4

squares. Assume both independent assortment and segregation are occurring.

Hands-On Labs SM-1 Lab Manual

70

EXPERIMENT 8: Phenotype and Genotype
Read the entire experiment and organize time, materials, and work space before beginning.
Remember to review the safety sections and wear goggles when working with chemicals.

Allow 40 to 60 minutes for this experiment

Objectives: To understand phenotype and genotype, and
To understand why you have certain characteristics

Materials: Student Provides: Self
Mirror

From LabPaq: PTC taste paper

Discussion and Review: Who you are is a product of both your physical nature and
your nurturing or training. Genetics is the study of your nature. By looking at some of
your physical features you can understand some of your genetics and why you have
certain physical features.

The study of genetics is one of the hottest areas of study in biology today. The recent
completion of the genome project, combined with growing interest in cloning and gene
replacement therapy, has generated great interest in genetics. In biology, genetics can
be divided into classical genetics (heredity) and molecular genetics. Heredity is
generally thought of as a study of parents and offspring and how their traits or
characteristics are related.

Two organisms can look alike but have different underlying gene combinations. The
way an organism looks and behaves is called its phenotype. The combination of genes
or alleles an organism contains for a particular trait is called its genotype. You cannot
always know an organism’s genotype simply by its appearance.

Mendel’s law of segregation explains the results of crosses between parents with similar
characteristics or phenotypes but whose offspring may have different characteristics.
He concluded that the two alleles for each trait must separate when gametes are
formed, and that a parent passes on at random only one allele for each trait to each
offspring. Each offspring therefore has two alleles, but one will dominate and determine
the phenotype. An organism is homozygous if its two alleles for a trait are identical, and
it is heterozygous for a trait if its two alleles for the trait differ from each other.

In this experiment, you will look at several human traits in order to observe Mendel’s law
of segregation. These traits are controlled by a single gene with two alleles and each
allele, if it is dominant in the pair, produces a distinct phenotype.

Hands-On Labs SM-1 Lab Manual

71

PROCEDURES: For each of the following traits determine your phenotype and if
possible your genotype. If you have a dominant phenotype, you may have either a
recessive allele and a dominant allele or two dominant alleles, whereas if your
phenotype is recessive, your genotype is recessive homozygous. Record your
observations in a table.

1. Dimpled chin: A cleft in the chin is a dominant trait.

2. Free ear lobe: For ear lobes to hang free is dependent on

a dominant allele. If two recessive alleles are present the
ear lobes are directly attached to the head.

3. Ability to taste PTC: Some people have the dominant gene that

allows them to detect the bitter taste of PTC while others do not. Put
a piece of PTC impregnated paper on your tongue for about five seconds. If you are
a taster you will know it.

4. Interlocking fingers: When the fingers are interlocked, some

people place the right thumb on top of the left (dominant allele);
others place the left thumb over the right (recessive allele).

5. Mid-digital hair: Some people have hair on the second (middle) joint of one or more

of the fingers, while others do not. The presence of hair is due to a
dominant allele and the absence of hair from all fingers is due to a
recessive allele.

6. Bent little finger: A dominant allele causes the last joint of the little

finger to bend inward toward the fourth finger.

7. Widow’s peak: The dominant allele produces a hairline with a point

in the center of the forehead (widow’s peak). The recessive allele
gives a continuous hairline.

8. Hitchhiker’s thumb: When you can bend the tip of the

thumb back 90 degrees in relation to the rest of the thumb
you are homozygous recessive for this allele.

9. Pigmented irises: When there is no pigment in the front part of the eyes and a blue

layer at the back of the iris shows through you are homozygous for the recessive
allele allowing blue eyes.

10. Long palmar muscle: Clench your fists tightly and examine the tendons running

over the inside of the wrists. If there are three tendons you have the recessive
alleles for the long palmar muscle, if there are only two tendons you do not.

Exercise: Refer to the previous experiment and construct a Punnett square showing
both the genotype and phenotype ratios possible if two heterozygous brown-eyed
individuals with dimpled chins were to have children. Your Punnett square will be 4 x 4
squares. Assume both independent assortment and segregation are occurring.

• SM-1 Manual COLOR 105 08-17-07

Discussion Questions:

What type of knowledge is being addressed? 


Types of knowledge that used are procedural, conceptual and implications. Enough information was provided in the procedure in order for the students to accomplish the task. The procedure was so created in such a way the students will be able to relate on the concepts on phenotype and genotype. At this point students gather the pieces together to come up with a more refined understanding on the concepts. At the end of the day, the students use these pieces to create implications. Exercises and home activities were created in the activity to reinforce and test such implications.

Are there issues related to the Processes of Science that might be problematic for students? Why? If so, how would you address them? 


Mendel’s law would be quite difficult to understand as far as addressing the engaging questions in section 3 in the lesson is concerned. The law was chosen not to be mentioned in the experiment .To address the problem, a simple 2×2 Punnet Square was used instead of 4×4 that was originally performed by the student to demonstrate the law. This was a key to understanding the objective questions.

What role did an understanding of cognitive stages have in the development of your lesson plan? 


The understanding of cognitive stages allows for a smoother, easier and logical framework of the lesson plan. The strong grasp of the subject matter allows better communication of the concepts with the procedure and exercises.

What types of scaffolding did you use? Why? 


Follow-up questions and exercises were provided as a means of reinforcing the concepts to student. The home activity also expands the student understanding beyond classroom. Students are taught to do extra mile with this group activity assignment.

Discuss how you used the 5E Model to develop this lesson plan. Be specific and provide a rationale for each step. 


ENGAGE

During the third section of the lesson plan on Introductory Discussion, questions were raised to engage the students reasoning skills. By this time, student should also wonder such questions and create curiosity among themselves. It then creates enthusiasm and excitement on what lies ahead of the activity.

It was followed by a sneak peek on what the experiment is about by defining what phenotype and genotypes are.

EXPLORATION

The procedure in the fourth section provides hands-on activity in a group environment that will allow them to grasp strongly the concepts through group discussions and brainstorming. It is in this way that students maximize the exploration process.

EXPLAIN

In the fifth section, there are sets of questions that test the students understanding on the activity. Students are encouraged to explain their idea to their groupmates to sharpen their grasp on the concepts.

ELABORATION

Students do the extra mile to elaborate their understanding through the home activity with real life situation. Using the parents and themselves as specimen will create more appreciation on phenotype and genotype.

EVALUATE

The essay part of the experiment evaluates how far the students have understood the concepts as far as meeting the activity objectives are concerned. Essay is a best finale activity for students to evaluate themselves by writing what they have learned so far.

Were there instances in which you chose to use a presentation instead of direct, hands-on experiences? If so, why did you choose to do so? (Note – you are NOT required to use a presentation in your lesson plan. Do so only if it makes sense to you.) 


I took the effort of finding photos that would clearly show the description of the dominant and recessive trait. Photos are good representation so that students can relate faster. If the dominant and recessive traits on harline,freckle and earlobes were described on texts, the student will figure it out at a much longer time.

What types of questioning are included in your lesson plan? Provide a rationale.

The factual type of questioning was used in the experiment. It is the lowest cognitive level of process so students in the fifth grade class should be able to answer questions with confidence. For instance in the procedure, the task as was simple as identifying 
which of the traits the students have and label themselves with their specific genotypes. To meet objectives, the evaluative type of questioning was also used. At the end of the day, students should be able relate this concepts to real life situations so that they would be able to appreciate the lesson. The activity of the Punnet Square was a perfect tool to accomplish this one.

What types of assessment are embedded in your lesson plan? What types were used in planning the lesson? What types of questions, if any, do you envision being used after the lesson plan has been “completed”?

A criterion reference type of assessment was used in the lesson plan. All the procedures, home activity and group discussion were designed to let the students meet the objectives and understand phenotype and genotype as well as how they applied in real life situations.

Reference:

Lepie, K (2013, July 2013). The 6 Types of Assessments (And How They’re Changing).

edudemic.com. Retrieve on September 17, 2013 from, http://www.edudemic.com/the-6-

types-of-assessments-and-how-theyre-changing/

Newer Views of Learning.-Types of Questions. www4.uwsp.edu . Retrieve on September 24, 2013 from http://www4.uwsp.edu/education/lwilson/learning/quest2.htm