Student Exploration: DNA Analysis
Vocabulary: allele, codon, DNA, DNA sequence, gene, genotype, identical twins, nitrogenous base, phenotype, trait
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
The two navy officers shown at left are identical twins. Why do you think identical twins look so similar?
Most brothers and sisters don’t look exactly the same. What causes most siblings to have different appearances?
Most of an organism’s traits, or characteristics, are determined by genes encoded in DNA. Traits are determined by the sequence of the four nitrogenous bases in the DNA molecule: adenine, thymine, cytosine, and guanine.
Except for identical twins, the DNA sequence of every individual is unique. In the DNA Analysis Gizmo™, you will analyze partial DNA sequences of frogs.
Select the POPULATION tab. What are the three main traits that vary between the frogs?
Which frog would you expect to have the most similar DNA sequence to frog A? Why?
Get the Gizmo ready:
Select the FIND THE TWINS tab.
Question: How are DNA sequences used to analyze relationships?
Observe: Look at the three frogs on the TWINS tab. How does their appearance compare?
Predict: What do you expect the DNA sequences of the three frogs to look like?
Identify: Drag frog A to the scanning station and click SCAN. Drag the resulting DNA sequence to the bin at the upper right of the Gizmo. Each band on the sequence represents a single nitrogenous base of DNA. The band is dark if that base is present and pink if that base is absent.
Scan frogs B and C. Drag their DNA sequences into the bin. If two frogs are identical twins, they will have exactly the same DNA sequence. Compare the three sequences.
Could any of these frogs be identical twins? If so, which frogs?