"This is my blueprint?"
Kana stared at the DNA model.
Milia nodded. "It's in every cell. Information to create you."
"But what information?"
Rei answered. "How to make proteins. That's the essence of genetic information."
Kana traced the helix with her finger. "Does this shape have meaning?"
"Double helix. The structure Watson and Crick discovered," Milia explained.
"Why double?"
"Because they're complementary pairs. A with T, G with C. If one is determined, so is the other."
Rei supplemented. "This enables replication. Unwinding the helix creates two templates."
Kana wrote in her notebook. "A-T, G-C"
"Connected by hydrogen bonds. A and T have two, G and C have three."
"Why different numbers?"
"Chemical structural constraints. But this difference affects stability."
Milia showed her tablet. "DNA sequence is a four-letter alphabet. A, T, G, C."
"Just four letters?" Kana was surprised.
"But the combinations are infinite. Human DNA has over 3 billion letters."
Rei continued. "That sequence specifies the order of amino acids. Three letters for one amino acid."
"Three letters?"
"Called a codon. For example, ATG is methionine."
Kana calculated. "With four letters in groups of three, 4×4×4 is 64 patterns?"
"Accurate. But there are 20 amino acids, so multiple codons can specify the same amino acid."
Milia drew a diagram. "DNA to RNA, RNA to protein. Called the central dogma."
"Dogma?"
"Doctrine. The basic principle of life information flow."
Rei explained. "First, transcription. DNA information is copied to RNA."
"Copy?"
"More precisely, only a part of DNA. Only the needed gene is copied."
Kana asked. "Is RNA different from DNA?"
"Structure is slightly different. A sugar called ribose, and U instead of T," Milia answered.
"U?"
"Uracil. Functions similarly."
Rei continued. "That RNA, messenger RNA, goes to the ribosome."
"Ribosome?"
"Protein synthesis factory. Translation happens here."
Milia assembled a model. "Reading the RNA sequence, arranging amino acids."
"How?"
"Transfer RNA. tRNA carries each amino acid."
Rei drew a diagram. "tRNA has an anticodon. A sequence complementary to the codon."
"Like a puzzle," Kana said.
"Yes. Molecular recognition is based on shape complementarity."
Milia continued. "Amino acids connect one by one, forming a polypeptide chain."
"That's a protein?"
"It folds and becomes a functional protein."
Kana looked at the DNA model again. "So all protein information is in here?"
"Not just that. Control information for when and how much to make," Rei said.
"Control?"
"Promoters, enhancers, silencers... regions that regulate gene expression."
Milia added. "Cells with the same DNA can become heart, brain, or liver because of this control."
Kana was moved. "Playing the same score with different instruments?"
"Beautiful metaphor," Rei acknowledged.
"There's also epigenetics," Milia continued. "Changing how genes are read without changing the DNA sequence."
"How?"
"Methylation, histone modification... chemical marks."
Rei organized. "DNA isn't a static blueprint. It's a dynamic, editable recipe."
Kana murmured. "A recipe to create me."
"And memories inherited from parents," Milia said quietly.
"Memories?"
"Memories of evolution. Hundreds of millions of years of trial and error engraved in this sequence."
Kana hugged the model. "Heavy..."
Rei and Milia smiled.
"The weight of life," Rei said.
The three fell silent. A four-letter alphabet spelling life.