An out-of-this-world activity
Discovery Place Science
Genetics is the study of genes and heredity. Our genes come from our biological parents and are found in our DNA, more specifically on our chromosomes.
All living things have DNA, which codes for all our traits, or characteristics. Human DNA is organized into 23 pairs of chromosomes; we get one chromosome per pair from each parent, making a total of 46 chromosomes. This is known as heredity. It is the reason why we look similar to but not exactly like our parents. The chromosomes we get are selected randomly, which is why there are so many different possibilities for how we look and behave.
Today, we will be creating an alien monster with different traits, providing learners with the opportunity to explore the basic concepts of genetics by creating their own monster.
This activity will take about 10 minutes to prepare and approximately 30 minutes of learning time. It is bested suited for students in upper elementary and middle school grades.
- Pony beads in different colors (*Note: If you do not have beads, you can use different colored paper or simply write down the traits on paper)
- Pipe cleaners or string
- Paper and drawing utensils
- Trait chart
Selecting the Parent Traits
- Cut 10 pipe cleaners each into 4 equal pieces. These will represent the 10 pairs of chromosomes for each parent. If you do not have pipe cleaners, you can also use string or slips of paper. We used different colored pipe cleaners for each chromosome, but you can use the same color for all.
- Look at the chart below. These are the different traits we will be looking at. Notice for each trait there are two or more possibilities. Each outcome depends on the combination of genes. (Note: We used a variety of different colored beads based on what we had. Feel free to use different colors. You can also stick to just two different colors of beads.)
- For each trait we will randomly select beads to determine what the parent aliens will look like (remember their characteristics were randomly received from their parents, too).
Let’s do the first one together. To determine the number of heads, place 2 Dark Blue beads and 2 Light Blue beads in a “mom” cup, and 2 Dark Blue and 2 Light Blue Beads in a “dad” cup. Without looking into the cup, randomly select two beads from each cup, and put them each on their own chromosome pipe cleaner.
Because both parents ended up with one dark blue and one light blue bead (Hh), they would both have 2 heads according to the trait chart. How many heads do your parent aliens have?
- Repeat the previous step for each of the traits EXCEPT for the Sex Chromosome 10. For the sex chromosome, Mom will have 2 white beads, and Dad will have 1 white bead and 1 clear bead.
- To keep track of your parent traits, you can fill out a chart like the one below. Notice the Body color trait is a little tricky. It depends on both Chromosome 8 and Chromosome 9. Feel free to draw what your parent aliens look like on a piece of paper.
Here is a picture of how our parent alien chromosomes turned out. Can you figure out the traits of our parents?
Making a Baby Alien
- For each trait of your baby alien, you will select one chromosome from Mom and one chromosome from Dad. Remember, this happens randomly.
- Let’s do the first one together. To determine the number of heads, place the two Mom alien Chromosome 1s (the chromosomes for number of heads) into the “mom” cup, and the two dad chromosomes in the “dad” cup. Without looking into the cup, randomly select ONE chromosome from each cup.
- Because our baby alien ended up with two Light Blue beads (hh) it would have 3 heads according to the trait chart, even though its parents both had 2 heads. How many heads does your baby alien have?
- Repeat the previous step for each of the traits. Again, you can fill out a chart like the one below to keep track of your baby alien traits. Draw your baby alien based on the traits you determined. How does you baby alien traits compare to your mom and dad alien traits?
Here is a picture of our baby alien chromosomes. Can you figure out the traits of our baby?
What is happening?
You may have noticed that for each trait there are specific possibilities. For example, when determining the number of heads there are 3 different combinations of bead colors you can have (2 Dark Blue, 2 Light Blue, or 1 Dark Blue 1 Light Blue). However, there are only 2 possibilities for number of heads (1 head or 2 heads). Why doesn’t the mixture of bead colors give you 1.5 heads? That is because often times in genetics we have a dominant gene and a recessive gene. When a dominant gene is present, the recessive gene is not expressed, in other words it doesn’t show up. In this case the Dark Blue bead is dominant, and the Light Blue bead is recessive.
However, genetics are complicated. We don’t always have simply a dominant or recessive gene. Sometimes both genes show up to code for something new, like we can see in the eye number, tail number and bottom half. Sometimes the outcome of one chromosome can completely mask another trait. For example, if you got “No Tail” for Chromosome 6, the “Tail Decoration” trait on Chromosome 7 will not be seen on your alien. The alien still carries the genes for tail decoration, and can pass it on to future generations, even if we can’t see it.
To complicate matters further, sometimes multiple genes need to work together in order to determine a trait. This is the case in the Body Color trait, where it depends on the outcome of both Chromosome 8 and 9. In fact, most human traits are determined based on multiple genes, which is why we have so many unique outcomes.
How to adjust for younger and older learners
Genetics can be very complicated. To make the concepts more concrete for young learners, make a genetics bracelet instead of a genetics alien. Use two different colors or types of beads for each trait. Use the same random selection process demonstrated in the activity above to create a “mom” bracelet and a “dad” bracelet. Make a “child” bracelet by randomly selecting bead colors for each trait based on the color combinations of the mom and dad bracelets. Ask your child what they notice about similarities and differences between the child and parent bracelets.
For more fun with genetics, check out the app, DNA Play, a great introduction for young learners to how changes in genes can affect the physical outcome of an organism.
For each parent combination there are multiple possibilities for the outcome of each child trait. For older learners, we can use a Punnett Square to calculate the probability of the outcomes. If you need a refresher on Punnett Squares, check out this video from TED-Ed.
For each trait make a Punnett Square using the parent alien characteristics. What is the likelihood that your baby alien trait would appear? Want to take it even further? Pick one trait to focus on and do the selection activity multiple times (20 or more). Does the distribution of actual outcomes match the predicted out comes? How does the distribution of outcomes change as you increase the number of trials?
Can’t get enough of Punnett Squares? Research Dihybrid Crosses and see if you can figure out the probabilities of two different traits together!