Student Exploration: DNA Fingerprint Analysis
Vocabulary: codon, DNA, DNA fingerprint, genotype, identical twins, nitrogenous base, phenotype, trait
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. The two navy officers shown at left are identical twins. Why do you think identical twins look so similar?
Identical twins look so similar because identical twins have the same genetic makeup, meaning, the same DNA (same nitrogenous bases). This is because by they are fertilized by the same egg, making them identical.
Most brothers and sisters don’t look exactly the same. What causes most siblings to have different appearances?
Most siblings have different appearances because each child inherits different gene from either one of the parents. These different genes can either be dominant or recessive depending on the parent which causes most siblings to have different appearances.
Most of an organism’s traits, or characteristics, are coded for by DNA. Traits are determined by a unique sequence of nitrogenous bases in the DNA molecule.
Except for identical twins, the order of every individual’s nitrogenous bases is unique. Scientists use this fact when studying DNA fingerprints—patterns of bands made from analyzing a strand of DNA. In the DNA Fingerprint Analysis Gizmo™, you will analyze DNA fingerprints of frogs. 1.
Select the POPULATION tab. What are the three main traits that vary between the frogs?
The three main traits that differ between the frogs are the spots on their body, the color of the eyes and the color of the skin.
Which frog would you expect to have the most similar DNA to frog A? Why?
Frog A would have the most similar DNA towards frog I. This is because they both contain the same traits, for example, both have spots on their body, both are color orange and have the same eye color as well.
Activity A: Identical twins
| Get the Gizmo ready: *
Select the FIND THE TWINS tab.
Question: How are DNA fingerprints used to analyze relationships?
Observe: Look at the three frogs on the TWINS tab. How does their appearance compare?
The three frogs contain the same traits. This means they all are colored orange, and have pink eyes. Also, all three frogs contain black spots on their body.
Predict: What do you expect the DNA fingerprints of the three frogs to look like?
Yes because I predict it from looking at the same traits they have.
Identify: Drag frog A to the scanning station and click SCAN. Drag the resulting DNA fingerprint to the bin at the upper right of the Gizmo. Each band on the fingerprint 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 fingerprints into the bin. If two frogs are identical twins, they will have exactly the same DNA fingerprint. Compare the three fingerprints.
Could any of these frogs be identical twins? If so, which frogs?
Yes because frogs with similar characteristics can contain the same DNA. The frogs that are identical twins are frog A and frog B.
Analyze: DNA is composed of four different nitrogenous bases. For the type of DNA fingerprint used by the Gizmo, a complete DNA fingerprint would have scan readouts for all four nitrogenous bases. Knowing this, why can you not be entirely certain the frogs are identical twins using the simplified fingerprints on the Gizmo?
This is because, on the Gizmo it only shows one DNA fingerprint scan, meaning that it scans only one out of the four nitrogenous bases. Therefore, it does not give accurate results, resulting certain frogs not being entirely identical twins.
Apply: Click New. For the new frogs, find the possible pair of identical twins.
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