The Genetics of Parenthood

Abstract:

Why do people, even closely associated people, look a little different from each other? The factor for these distinctions in physical qualities, or look, (called phenotype) is the various mix of genes (the genotype) possessed by each individual. All of your genes are segments of DNA located on your chromosomes. To show the significant variety possible when you start to integrate genes, you and a classmate will develop the genotypes for a prospective offspring. Your child will get a random combination of genes that each of you, as genetic parents, will contribute.

Each regular person has 46 chromosomes (23 sets, which we call diploid or 2n) in each body cell. One set of your chromosomes mostly identifies your sex, hence, this set is called the sex chromosomes. The other 22 pairs carry all the other genes that automatically determine everything else about you, thus, they are called autosomes.

In forming the gametes (egg or sperm), one of each chromosome pair will be given by each parent, so these cells, or gametes, have just 23 single chromosomes (haploid or n).

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In this way, you contribute half of the hereditary info (genotype) for the kid; your partner will contribute the other half. Due to the fact that we don't know your genuine genotype, we'll presume that you and your partner are heterozygous for every single facial quality; heterozygous ways that in each of your body cells you carry one copy of the gene for one kind of body quality and another copy of the gene for a slight difference because trait.

Which one of the two offered copies you contribute to your baby through sperm and egg is random, like turning a coin. In this lab, we are keeping it easy - there are just 30 gene sets and 30 inheritable traits represented, however in truth there are countless different gene pairs, and so there are millions of possible gene mixes!

Purpose:

A number of inheritance patterns are represented in this simulation. Inheritance patterns of the characteristics utilized in this simulation have actually been streamlined to work as a design; actual inheritance is even more complicated.

Materials:

- 2 coins (for mother and dad gamete contribution).
- Drawing paper or white boards.
- Pens/crayons.

Procedure/Data:.

Tape all your work on each moms and dad's data sheet.

1. First, determine your baby's gender. Remember, this is determined entirely by the father. The mother always contributes an X sex chromosome to the child. Heads = X chromosome, so the child is a GIRL (an XX genotype) Tails = Y chromosome, so the child is a BOY (an XY genotype) Fill in the results on your data sheet.

2. Name the child with a first and last name.

3. Now, determine the child's facial characteristics by having each parent flip a coin for each of the traits on the given “Trait List” sheet.

Heads = child will inherit the dominant version of the trait (i.e. B or N1) in a pair Tails = child will inherit the recessive version of the trait (i.e. b or N2) in a pair

On the data sheet, circle which allele, or version of the trait that each parent will pass on to the child and write the child's genotype.

4. Using the information on the “Trait List”, look up and record the child's phenotype and record the phenotype. **Some traits follow special conditions, which are explained in the guide. 5. When the data sheet is completed, draw your child's portrait as he/she would look as a teenager. You must include the traits as determined by the coin tossing. Write your child's full name on the portrait.

Fill in data table as you determine each trait described. Do not simply flip the coin for all traits before reading the “Trait List”, because some traits have special instructions. Believe it or not, it will make your life easier if you follow directions. In the last column, combine the information and draw what that section of the child's face would look like.

Analysis/Conclusion: (Copy and Complete)

1. What percentage does each parent contribute to a child's genotype?

2. Explain how this does and does not relate to the process of mitosis.

3. How many individual chromosomes are found in every cell of the human body (except for the sperm and eggs)? How many pairs is this?

4. Now we’re going to relate what we know to a basic math concept. If we use “2n” to represent the 46 chromosomes found in normal human body cells, then how many chromosomes would “n” represent?

5. Would you use “n” or “2n” to represent 23 pairs of chromosomes? 6. Using “n” or “2n”, how many chromosomes would a cell have to have at the end of interphase, and at the start of mitotic division? 7. Using “n” or “2n”, how many chromosomes does each daughter cell have after mitosis?

8. Using “n” or 2n”, how many chromosomes does a sperm have?An egg have?

9. Explain with your reasoning why or why not mitosis would work to create sperm and eggs.

10. Write an analysis/conclusion about the lab. This will be approximately 2 paragraphs and should include a brief explanation about the purpose related to the abstract (why did we do the lab?) and an explanation of the results (what was the data?) in relation to what really occurs in reality. Teacher Resource Sheet

This is a simulation that easily captures student interest and can be varied to meet different ability levels. Making the assumption that the P (parental) generation is heterozygous at all loci and that independent assortment occurs (no linkages), students flip coins to determine which allele they will pass on to the F1 generation, and draw the resulting child's face. Emphasize the variation which occurs, reminding the students that these children are genetic siblings since all parents have identical genotypes. Several inheritance patterns are represented in this simulation, and it is important to review these with the students beforehand. Inheritance of the traits used in this simulation have been simplified to serve as a model; actual inheritance is far more complex and students may need to be reminded about this in case they get overly concerned about their own traits. • Dominant: allele which masks the expression of another; represented by capital letters (R, V)

• Recessive: allele which is expressed only if both parents contribute it; represented by small letters (r, v) • Incomplete dominance: phenotype of the heterozygote is an intermediate form; represented by capital letters and subscripts (C1, C2); an example is red color tints in the hair • Polygenic: several genes contribute to the overall phenotype; an example is skin color • Sex-linked: commonly applied to genes on the X chromosome, the more current term is X-linked; genes on the Y chromosome are holandric genes; no examples in this activity • Epistasis: one gene masking the effects of another; an example is hair color to red color tints Target Age/Ability Group

High School Biology, all levels
Class Time Required:
At least 1-2 class periods
Activity ideas after completing the data sheets

1. One student draws the child's face; partner writes a biography of the child at age 30 - what is the child like, what have they accomplished, what are their dreams...this can also bring about interesting discussions on how the students feel about their parents and their perceptions of parenthood. 2. Do the lab twice, comparing the genotypes and phenotypes of the resulting siblings. 3. "Marry" the children off, to produce an F2 generation (grandchildren). 4. Instead of drawing the face, decorate an egg or a five pound package based on the child's traits. It can then be used in the activity "Problem Solving in Genetic Disorders" by Nikki Chen, or "One + One = One" by Dorothy Josephine Cox.

References
Adapted from materials from Joan Carlson, Jack Doepke, Judy Jones and Randyll Warehime. Lewis, Rikki. 1994. Human Genetics: Concepts and Applications. Wm. C. Brown Publishers. Stine, Gerald J. 1989. The New Human Genetics. Wm. C. Brown Publishers.