Science (For Roel)

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Hands-On Labs SM-1 Lab Manual

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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

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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

Assignment Instructions

For your midterm develop a lesson plan on Phenotype and Genotype for elementary students. For purposes of this activity, assume you are teaching a fifth grade class.

Design your lesson plan with the following elements / questions in mind. Also, elaborate on each of these elements / questions.

1. What type of knowledge is being addressed? 
 

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

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

1. What types of scaffolding did you use? Why? 
 

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

1. 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.) 
 

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

1. 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”?

1. These questions need not be answered in any specific order. You can answer them separately from the lesson plan, or embed them as notations in the lesson plan you submit. The format, as usual, is up to you.

When you have completed your midterm, submit it as a word document.