PARLOR GENOMICS
Put your intuitive understanding of DNA to the test
INHERITED TRAITS
 |
In Muggsville, home base for the fruitful Mugg family, it’s easy to tell which residents are cousins. If two Muggsvillers are cousins, their faces share two of three identifying characteristics: eye color, hair color, and head shape. For example, in the nine “Mugg shots” in the illustration at right, Muggsvillers 4 and 5 are cousins because their faces are identical except for eye color. Muggsvillers 1 and 2 are not cousins because their faces differ both in shape and eye color.
1. [Easy] Which of the Muggsvillers have just one cousin in the group?
2. [Challenging] Who has the most cousins? (Hint: None of the Muggsvillers has more than four cousins in the group.)
3. [Difficult] How can you arrange these nine Muggsvillers in a row so that each is placed only next to cousins? (Hint: What must be true of the first and the last Muggsvillers in the row?
GENETIC TRANSCRIPTION
 |
The body stores instructions for making a human in DNA, a long molecule that consists of a sequence of base pairs—adenine and thymine, guanine and cytosine—which are represented by the symbols A, T, G, and C. The DNA inside a human cell nucleus would be about six feet long if you could stretch it out. To fit in the cell, DNA folds itself in a tightly coiled tangle.
The matrix shown here has just two symbols, green and purple, which are packed in a 10-by-15 grid. These symbols form twisted paths through the matrix. Can you find the routes described below?
1. [Easy] Travel from the green start dot to any of the dots in the bottom row by following a path formed by the repeating pattern green, purple, green, purple. You may move only left, right, up, or down (not diagonally) from one symbol to the next. The first few steps are shown.
2. [Challenging] Find the shortest possible path that follows the repeating pattern green, green, purple, purple, green, green, purple, purple from the green start dot to any of the dots in the bottom row. (Hint: The shortest path uses 23 dots, and the first five moves are right, right, down, down, left.)
3. [Difficult] Find the shortest possible path that follows the repeating pattern green, green, purple, green, green, purple from the green start dot to any of the dots in the bottom row. (Hint: The shortest path has 26 dots, and the first three moves are right, down, down.)
JIGSAW SEQUENCING
The human genome is about 3 billion pairs long. To decode this mass of information, researchers cloned segments of DNA and cut them into shorter pieces. About 500 bases on each piece of DNA were decoded using a gene sequencing machine. Then the millions of segments were put back into their original order, like pieces of a jigsaw puzzle.
How do you assemble a million-piece jigsaw puzzle when you don’t even know what the final picture looks like? The solution was ingenious: Search for a sequence at the end of one segment that matches the sequence at the beginning of another segment. If the two sequences match, you can guess that the two segments fit together with a common overlapping sequence.
Use a similar approach to assemble the puzzle below. Fit the nine pieces into the 10-by-10 grid so that adjacent pieces overlap by one column or one row of squares that match exactly. (Pieces may not be rotated.) When the puzzle has been finished, the shaded squares will spell a five-letter word that’s related to DNA. The first two pieces have been filled in. Note how the right edge of piece 2 overlaps and matches the left edge of piece 1.
