The Genetics of Parenthood

Baby Genetics
Lenore Kop and Thomas Crowley
1994 Woodrow Wilson Collection
View the original

Welcome to On-Line Lab 13. The one in class is extremely similar to "The Genetics of Parenthood" from the Woodrow Wilson Collection, where I've borrowed their graphics below. I don't know what the origin of the exercise we're using in class, but to see the WW version, click the link above.

Both versions begin with the assumption that the P (parental) generation (you and your paartner) is heterozygous at all loci and that independent assortment occurs (no linkages), We will begin by examining OUR personal phenotypes and estimate our genotypes from this so as to create a more realistic outcome. Students flip coins to determine which allele they will pass on to the F1 generation, and draw the resulting child's face.

Several inheritance patterns are represented in this simulation, and it is important to review these. 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

Materials

2 coins (preferably different kinds to keep track of mother/father contribution)
The Genetics of Parenthood Guidebook (see below)
Drawing paper or white boards
Pens/crayons (Crayola has a "My World Colors" set for various skin/eye colors)

The Genetics of Parenthood Guidebook

Why do people, even closely related people, look slightly different from each other? The reason for these differences in physical characteristics (called phenotype) is the different combination of genes possessed by each individual.

To illustrate the tremendous variety possible when you begin to combine genes, you and a classmate will establish the genotypes for a potential offspring. Your baby will receive a random combination of genes that each of you, as genetic parents, will contribute. Each normal human being has 46 chromosomes (23 pairs - diploid) in each body cell. In forming the gametes (egg or sperm), one of each chromosome pair will be given, so these cells have only 23 single chromosomes (haploid). In this way, you contribute half of the genetic information (genotype) for the child; your partner will contribute the other half.

Because we don't know your real genotype, you will compare your face (with the help of your partner) to the traits. For each trait, if you have the recessive form, put down the two recessive alelles in the chart. If you have the dominant trait, flip a coin: heads you are homozygous dominant (two CAPITAL alelles); tails you are heterozygous for that facial trait (one letter of each). Which one of the two available alleles you contribute to your baby is random, like flipping a coin (if you are heterozygous). In this lab, there are 36 gene pairs and 30 traits, but in reality there are thousands of different gene pairs, and so there are millions of possible gene combinations!

Procedures

Record all your work on each parent's data sheet.

Determine your personal phenotypes and genotypes for each trait. List them in the chart as appropriate

Determine your baby's gender. Remember, this is determined entirely by the father. The mother always contributes an X chromosome to the child.

Heads = X chromosome, so the child is a GIRL

Tails = Y chromosome, so the child is a BOY

Fill in the results on your data sheet.

Name the child (first and middle name; last name should be the father's last name).

Determine the child's facial characteristics by having each parent flip a coin as needed (only for heterozygous parental traits).

Heads = child will inherit the first allele (i.e. B or N1) in a pair

Tails = child will inherit the second allele (i.e. b or N2) in a pair

enter each parents contribution in the appropriate space on the worksheet.

Using the information below, look up and record the child's phenotype on the data sheet.

Some traits follow special conditions, which are explained in the below.

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.

The Genetics of Parenthood Data Sheet

Parents _____________________________ and ______________________________

Child's gender _____ Child's name _________________________________

Fill in data table as you determine each trait described in the Guidebook. Do not simply flip the coin for all traits before reading the guide, 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.

Questions:

What percentage does each parent contribute to a child's genotype?
Explain how/what part of your procedures represents the process of meiosis.
Using examples from this activity, explain your understanding of the following inheritance patterns:
Compare the predicted phenotype ratio (Punnett squares) to the actual ratio (class data) for the following traits: