Materials Included In Kit

Additional Materials Required

Prelab Preparation

Cut along the dotted lines on each genome set. The twelve cards in each genome should be placed in a zipper-lock plastic bag and labeled Male 1, Female 1, etc. If cards get mixed up, the codes M₁, M₂, F₁, F₂, etc. on the cards can be used to separate the cards into male and female again.

Safety Precautions

This simulation exercise is safe. Follow all normal laboratory safety rules.

Disposal

The male and female genome materials can be reused many times.

Teacher Tips

• Enough materials are provided in this kit for 30 students working in pairs or for 15 groups of students. All materials are reusable. The laboratory activity can be reasonably completed in one 50-minute class period.

• This activity can be easily be extended in several ways. Data can be pooled for the entire class for one or more of the traits. Actual results can be compared with predicted results for the trait in question. Male and females could be compared for all the children produced in the class. How close does the sex ratio come to 50:50? Gene pool considerations could be studied and Hardy-Weinberg principles applied for the entire population. How does the second generation compare to the first?
• Groups could interact with other groups and mate first generation children to see what happens when grandchildren are produced. How do the grandchildren compare to the original parents?
• The question in the introduction of the activity (relative finger length) is an interesting sex-influenced (not sex-linked) trait. In males, the allele for a short index finger is dominant. In females, it is recessive. In rare cases each hand may be different. If one or both index fingers are greater than or equal to the length of the ring finger, the recessive genotype is present in males, and the dominant present in females.

Answers to Questions

1. Was child 1 male or female? Explain how you know.

The answers will vary. Males will have an XY chromosome pattern and females will have an XX chromosome pattern. This is obtained from the color blindness genes.

2. Are child 1 and child 2 the same sex or different sexes? Explain the probability that two children in a row will be the same sex.

Answers will vary. The probability of two children in a row being of the same sex is ½ since there are four possible patterns MM, MF, FM, FF—two of these patterns have children of the same sex.

3. How many genotypes are identical in the two children?

How many genotypes are different in the two children?
How many phenotypes are identical in the two children? 
How many phenotypes are different in the two children?
Explain why their genotype and phenotype numbers are different.

Answers will vary. Because of the variety of the modes of inheritance, the two children will likely be quite different!

4. Does either child have a trait that neither parent had? Explain how this could happen.

Since one allele comes from each parent the child can easily be different than one of the parents, especially if two heterozygous parents have a homozygous recessive child for a given trait.

5. Do both children have the same blood type? Does either child have a blood type not like either parent? Explain how this could happen.

Answers will vary but since the type A and type B bloods can have various genotypes it is possible to have children that are not Type A or Type B. Similarly Type AB crossed with Type O will not produce either Type AB or Type O children.

6. Use the back of this worksheet and colored pencils to draw a sketch of the two children.

Drawings will vary, but the two children will not look identical.

Introduction

How did you end up with an index finger that is shorter than your ring finger? Is this an inherited trait? Does your mother have the same trait? What about your father?

Concepts

• Dominant/recessive

• Alleles
• Genotype vs. phenotype

Background

Gregor Mendel was a pioneer in determining basic principles of heredity breeding garden peas. Mendel cross-pollinated two contrasting, true-breeding varieties. Take purple and while flowers for example. The two true-breeding parents are referred to as the P generation (parental generation) their hybrid offspring are the F₁ Generation. Self-pollination of the F₁ generation produces the F₂ generation.

Alternative versions of genes, known as alleles, account for variations in inherited characteristics. The gene for flower color in pea plants exists as two versions, both the purple and white. Each organism possesses two alleles for each gene, one inherited from each parent. If the two alleles are at a different locus the dominant allele will determine the organism’s appearance and the recessive allele has no noticeable effect on the organism’s appearance. The physical appearance of an organism is known as its phenotype. For example, viewing that the flower is purple explains its phenotype. Its actual genetic makeup or set of alleles is known as an organism’s genotype.

An organism which has a pair of identical alleles for a characteristic is known as homozygous for the gene controlling that characteristic. For example, the parental generation is homozygous for color is PP. An organism that has two different alleles for a gene is heterozygous for that gene (Pp).

The final component of Mendel’s Model states that the two alleles for a heritable character separate during gamete formation and end up in different gametes. See the following figure for further explanation of Mendel’s Law of Segregation.

Figure 2 displays the results of the F₂ generation. It also compares the differences between genotype and phenotype. An organism may have the same phenotype while having a different genotype.

This activity assumes an understanding of the basic genetic concepts such as incomplete dominance, sex-linked, sex determination and independent assortment. The twelve traits used in this simulation are described in Table 1.

Materials

Safety Precautions

This lab is a pencil and paper activity and is considered non-hazardous. Follow all normal laboratory safety rules.

Procedure

1. Your lab team should have one simulated male genome and one simulated female genome, each in a labeled storage bag. The genome of each individual is represented by the gene symbols printed on both sides of the cards in each storage bag. There should be twelve cards in each bag. The two genes on each card (one on each side) represent the allele pair possessed by the individual for one specific trait.
2. Record the genotype of the male (father) in the space provided on the Baby Genes Worksheet. Do this by looking at both sides of every card for the father and recording the allele pair on the worksheet.
3. Once the complete genotype has been recorded, write the phenotype of the father for every trait in the appropriate space on the worksheet. Replace the cards into the male storage bag.
4. Record the genotype and phenotype of the mother (female) following the same procedure used for the father in steps 2 and 3 and then replace the cards into the female storage bag.
5. These two simulated parents are going to produce two children. Select the genes that the first child will receive from the father. This must be done strictly by chance and each trait must be selected independently. Carry out the selection process by having one team member hold the storage bag open while another team member selects a card from the bag without looking. Have the person place the card on the table without looking at the card. Record the allele that is facing up. This is the gene that will be contributed to the offspring in the father’s sperm cell. Continue this “blind” selection of the father’s contributed genes one at a time placing them on the table top. Record the selected sperm alleles for the first child in Part II on the Baby Genes Worksheet. Return all the cards to the “father” storage bag when all the selections have been made.
6. Determine the alleles contributed to the first child in the mother’s egg following the same random selection process. Use the bag of alleles containing the mother’s alleles. Record the random egg selections on the worksheet for the first child. Place the alleles back into the “mother” storage bag.
7. Simulate fertilization of the egg by the sperm by combining the selected alleles to form the genotype of the first child. Use the allele from the father’s sperm and the mother’s egg for each trait and record the genotype of the first child for each trait.
8. Describe the phenotype for each trait for the first child at the appropriate place on the Baby Genes Worksheet.
9. Repeat steps 5–8 for a second child from the same father and mother. Be sure to make the selections “blindly” and randomly. Mix up the cards in the storage bag before making the second selections. Record the results for the second child in Part III of the worksheet.
10. Analyze the two children resulting from your selections by answering the questions on the Baby Genes Worksheet.
11. Return all alleles to their appropriate storage bags for future use and return them as directed by your instructor.

Student Worksheet PDF

10349_Student1.pdf