Monday, January 19, 2015

Family Traits activity

This was an activity I thought of to show how different combinations of traits can produce such differing results in siblings. There are several variations of this idea online, but nothing exactly like what I wanted, so I came up with this spreadsheet for our use. It's vastly simplified from real life, of course, but it was still fun to do.
We started out with a master list of alleles, and which were dominant and which were recessive.

Then I drew about eight different "parents." If Sam hadn't been so busy, I would have had him draw them, and then we would have had something worth sharing here. But since the focus was more on individual traits than a lovely artistic whole, it worked out okay. I made the parents very exaggated-ly have their phenotypes (big nose, hair color, etc.) and then I wrote their genotypes on the page so you could tell if they were homozygous or heterozygous.

Then we put tape on coins to show D for dominant and R for recessive. (You could just say "heads is dominant" or whatever, but actually putting the letters on helped make it more clear, I thought.)
Each set of parents had six "children." I made a spreadsheet with a list of all the alleles for each child, plus a place to write the genotypes and circle the phenotypes. Then there was a large space to draw the phenotypes for each child.

To make your "family," you would go through the following steps:
  1. Choose (at random) two parents from the "parents" pile.
  2. Flip a coin to determine the first child's sex. (E.g., assign female to heads/"D" and male to tails/"R")
  3. Check the genotypes of the parents. If either parent is homozygous dominant, write down one dominant allele for the child to inherit. If either parent is homozygous recessive, write down one recessive allele for the child. If a parent is heterozygous, flip a coin to see which allele the child will inherit. (So, if both parents are heterozygous, flip the coin twice to see which two alleles the child gets.)
  4. Once the genotype for the child is determined, circle the phenotype.
  5. Repeat steps 3-4 for each trait on the list.
  6. Draw what the child will look like.
  7. Repeat steps 2-6 for each child of these parents.

Even though it's a little bit involved, this isn't hard to do once you understand what you're doing. I had the children work in pairs so the bigs could help the littles, but everyone had fun flipping the coins and drawing the results.

Two related videos we enjoyed:

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