Copy of DNA Analysis Student Exploration Sheet

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.) 1. The two navy officers shown at left are identical twins. Why do you think identical twins look so similar? So I think identical twins look so similar because identical twins do have the same genetic makeup. For example the same DNA (same nitrogenous bases). 2. Most brothers and sisters don’t look exactly the same. What causes most siblings to have different appearances? I think brothers and sisters don’t look exactly alike because everyone like parents actually has two copies of most genes. Gizmo Warm-up 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. 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 eyes and the color of the skin. 2. Which frog would you expect to have the most similar DNA sequence to frog A? Why? Mostly frog A would have the most similar DNA towards frog l. And they both contain the same traits like both have spots on their body. Activity A: Identical twins Get the Gizmo ready: ● Select the FIND THE TWINS tab. Question: How are DNA sequences used to analyze relationships? 1. Observe: Look at the three frogs on the TWINS tab. How does their appearance compare? All three frogs have the same exact traits. They all colored orange have pink eyes, and contain black spots on their body. 2. Predict: What do you expect the DNA sequences of the three frogs to look like? i expect them to look different 3. 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? I think yes because frogs with similar charcteristics can contain the same DNA. 4. Analyze: DNA is composed of four different nitrogenous bases. For the type of DNA sequence used by the Gizmo, a complete DNA sequence 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 sequences on the Gizmo? This is because on the Gizmo it shows one of the DNA fingerprint scan meaning that it scans only one out of the four nitrogenous bases. 5. Apply: Click New. For the new frogs, find the possible pair of identical twins. A. Which two frogs could be identical twins? A and B because their DNA strands are exactly the same. B. How do you think DNA sequences can be used in the real world to identify relationships between individuals? It can be used in the real world to identify relationships between individuals by determining if the individuals are related. Activity B: Get the Gizmo ready: Comparing genes ● Select the POPULATION tab. Introduction: In this frog population, traits such as eye color, skin color, and spots are coded for in the DNA. For each gene, there are two alleles, or versions. The sequence of nitrogenous bases in a strand of DNA make up an organism’s genotype. The physical traits resulting from the genotype makes up the organism’s phenotype. Question: How are DNA sequences used to analyze traits? 1. Observe: Describe frog A’s phenotype. Frog A thing has a presence of spots located on the body and the eye color is pink and I think the skin is orange. 2. Compare: Which frogs share frog A’s skin color, but not its eye color or spots? Frogs H and P.3 3. Analyze: A group of three consecutive nitrogenous bases in a strand of DNA is a codon. In a real organism, genes are made up of hundreds of codons. In the Gizmo, a single codon codes for a trait. Scan frog A and the two frogs that share only frog A’s skin color. Turn on the Comparison guides, and compare the three DNA sequences. Codon 1 is made up of bases 1–3, codon 2 is made up of bases 4–6, etc. The last two bases are part of codon 7, which was cut off when the scan was made. A. Which codon or codons are identical in all three frogs? Codon 6 for frogs A I and J are identical in all three frogs. B. Scan more frogs with orange skin until you are confident that you have identified the correct codon that represents the allele for orange skin. Describe the results: All orange skinned frogs C. Which codon codes for orange skin in this frog population? Have the codons 6 even the ones with no spots and different eye color. 4. Analyze: Pick out two frogs with blue skin and nothing else in common. A. Which codon do they share? Canons 4 and 6 were mostly common in frogs G and D B. Scan two more frogs with blue skin to confirm you have identified the correct codon. Describe the results: And i think all 4 frogs which include G, D , K and H have condon 6 common. (Activity B continued on next page) Activity B (continued from previous page) 5. Collect Data: Fill in the column for orange skin in the table below. For the codon pattern, shade in the dark bands but not the light colored bands. Then, continue scanning frogs until you are able to complete the rest of the columns in the table. Codon Bases Orange skin Blue skin Pink eyes Green eyes Spots No spots 7 7 3 3 1 1 A,B,E,F,I,J,M ,N C,D,G,H, K,L,O, P A,E,M,C, G,K,O B,F,J,N,D,H, L,P A,B,C,D ,I,J, K,L E,F,G,H,M ,N,O,P 1 1 0 0 Codon pattern 0 0 5 6. Analyze: Does the same codon always control skin color, eye color, and the presence of spots? Why do you think this is the case? I think yes because the same codon does always control skin color, eye color and the spots. Codons code for amino acids in the organism, especially since the genetic code is universal. 7. Apply: Look at the DNA sequence at right. Describe the frog’s phenotype. Blue skins spots and pink eyes 8. Interpret: Click New to get a new population. Again, determine which codons code for which traits. Compare the results with the table above. How do the codons used to code for skin color, eye color, and spots in this new population of frogs compare to the first population you tested? It could be used to find genes segments of DNA that code for a specific protein or phenotype. so i think if the region of DNA has been sequenced. 9. Explain: Suppose a biologist found a rare frog and wanted to determine which species it belonged to. How could a biologist use a DNA sequence of the frog to accomplish this task? I think she would compare the DNA to that or other frogs which it seemed to be related to . but the differences in DNA indicate different species. 10. Extend your thinking: What other applications of DNA sequences can you think of? So if a region of DNA has been sequenced it could be screened for characteristics features of genes.