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Print a copy of the “genome” game board for each player.
For Class: We have cards for Complex I, Complex III, Cytochrome C and Complex IV in four colors.
Outside of Class: Several decks of cards need to be used. Select 4 numbers (e.g. A, 2, 3, 4) to represent the different gene types, and separate them from several decks of cards. Put aside the other cards, just using the selected numbers, choosing which number represents which complex or Cytochrome C.
- Each card type represents a different suite of genes, and each color/suit represents a different version of the genes.
- Each player is an organism with 4 suites of genes represented by one (or two) card of each type. Cards are placed face up on the player’s genome so all players can see them.
- To remain alive, a player has to have at least 2 gene suites of the same suit. (This rule vaguely mimics the need for genes that work together.)
- The first player who has the same suit in all 4 gene suites wins.
- Each player is also a scientist and records their choices (if any), deaths and wins. Notes and observations should also be added about interesting events.
Each group will play 3 games over 2 class periods:
Game 1: Asexual Reproduction with Mutation Only:
Bacteria, Archaea, and some animals and plants can reproduce without exchanging genes with others of the same species. The offspring have identical genes as the parent. Evolution is through mutation only (in this version of the game), and we are ignoring natural selection for now, except for winning and losing.
- Each player starts with 1 card for each gene suite.
- At each turn, the player mutates by drawing a card from the deck and replacing the equivalent gene suite with the new one.
- If a player ends their turn with no two gene suites of the same color/suit, they die and are eliminated from the game. If they end their turn with all gene suits of the same color/suit, they win.
- Play for 5 rounds. This is a game of pure chance.
Game 2: Sexual Reproduction
This is how we usually think about gene transfer. Each offspring has genes from two parents. This is a good way to get diverse combinations of genes.
- Each player starts with 2 cards for each gene suite (representing the two chromosomes in animals.)
- At each turn, the player can choose to reproduce with another player or to mutate.
- To reproduce, the player whose turn it is (player A) chooses another player to exchange cards with (player B). A randomly chooses one card from each gene suite. Then B randomly chooses one of each of A’s genes in a similar fashion. (This vaguely represents a random gene distribution in the formation of eggs or sperm but also selection in reproduction, because a player can choose with whom to exchange genes.)
- To mutate, the player draws a card from the deck and discards one of the cards representing the equivalent gene suite that they drew. The card to discard should be randomly chosen.
- If a player ends their turn with no two gene suites of the same color/suit, they die and are eliminated from the game. If they end their turn with all gene suites of the same color/suit, they win.
- The players can add a new rule if they agree to it unanimously.
- Play for 10 minutes or so.
Game 3: Asexual Reproduction with Mutation and Lateral Gene Transfer
Lateral gene transfer is a very important evolutionary influence. It allows innovations to be shared across species and allows organisms to gain new functions without the slow process of chance mutations. For example, lateral gene transfer is a key way resistance to antibiotics spreads and has also played a key role in major evolutionary events such as the origin of oxygenic photosynthesis.
- Each player starts with 1 card for each gene suite. (Bacteria and Archaea do not necessarily have two copies of each gene.) Two cards are turned face up next to the deck of remaining cards and are the discard piles. The top card on each discard pile is available for lateral gene transfer.
- At each turn, the player can choose a lateral gene transfer from the discard pile or a mutation from the draw pile.
- For a lateral gene transfer, the player chooses one of the upturned cards for their genome and discards the equivalent gene suite from their genome. They can discard it on either discard pile, and it becomes available as a lateral gene transfer for subsequent players.
- For a mutation, the player draws a card from the deck and replaces their equivalent gene suite with the new one. They discard the old one onto either of the discard piles, and it becomes available as a lateral gene transfer for subsequent players.
- If a player ends their turn with no two gene suites of the same color/suit, they die and are eliminated from the game. If they end their turn with all the same color/suit in all 4 gene suites, they win.
- Play for 10 minutes or so.
Talk about the different strategies for the games, and choose one you want to share with class in discussion. What insights does it give you to evolutionary processes?
Additional Information: (not necessary for playing the game)
The gene suites we are playing with represent key functions in the metabolic process of aerobic respiration, where organisms use O2 and organic matter to create energy. Specifically, the electron transport chain used is part of oxidative phosphorylation, which helps the cell make ATP. Complexes I, III, and IV are coded by suites of genes. In contrast, Cytochrome C is coded by a single gene. Q stands for quinone, which is a suite of related molecules that can be absorbed by the cell or manufactured using enzymes. There is not a specific gene coding for that molecule, but there are genes that code for the biosynthesis of quinones.
The premise of this game is to illustrate how different reproductive strategies affect gene diversity. It does that to some extent, but there are also aspects of the game that do not mimic what actually happens in biology. Specifically, most mutations occur due to errors in how the DNA is copied by the enzyme called DNA polymerase. Some also occur from DNA damage due to environmental factors like radiation and the chemical environment.
Most mutations only alter the function of a small part of a complex at most, so the game is not scientifically rigorous for complexes I, II, and IV, since we are assuming that the mutations affect the whole complex. Sometimes mutations do lead to a functional change in a suite of genes. Suites of genes that function together are often located next to each other on the DNA strand. Sometimes, when these strands are copied, different bits of DNA get inserted between or within the genes. This can disrupt the translation of the gene suite into a functional complex. This mutation mechanism is more appropriate for the complexes represented in the game, but it still is not very scientifically rigorous.
The rules for winning and losing represent a very simple, inaccurate model for natural selection. In general, suites of genes that function together work better overall when they have evolved together. Small mutations that make the processes more efficient accumulate in all the gene suites. The colors/suits in the game represent different versions of the gene suites, some evolving together (the same color) and others not (different colors). The collection of gene suites that all evolved together represents an efficient pathway for respiration in the game, thus, a winning genome. Having no gene suites that evolved together represents particularly inefficient respiration, thus, a losing genome. There are many ways natural selection could be improved in the game!