Transcription

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Transcription is the process by which DNA makes a copy of its message in the form of mRNA, which carries instructions to build proteins

The cell needs DNA’s instructions to make proteins, but DNA stays in the nucleus. Think of DNA as an instruction manual that never leaves the library, so the cell makes a working copy called messenger RNA, or mRNA.

Because DNA is double-stranded, it must first unwind. An enzyme called RNA polymerase attaches to the DNA and reads just one strand, letter by letter.

As RNA polymerase reads the DNA, it builds a copy in the form of mRNA. The rules are simple: A pairs with U, T with A, G with C, and C with G. Bit by bit, the mRNA strand grows, carrying DNA’s instructions.

When RNA polymerase reaches a stop signal on the DNA, it stops making mRNA. The mRNA then detaches from the DNA, is processed in the nucleus, and exits through nuclear pores to the cytoplasm for protein production.

Overview

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Transcription

Transcription is the first step in the process of gene expression, where information from a DNA sequence is copied into messenger RNA (mRNA). This process takes place in the cell nucleus and is essential for producing proteins that carry out cellular functions. During transcription, the enzyme RNA polymerase binds to a specific section of DNA called the promoter. It then unwinds the DNA and uses one of the strands as a template to synthesize a complementary RNA strand. Once the mRNA is formed, it exits the nucleus and travels to the ribosome, where it will be translated into a protein. Transcription is a key mechanism that ensures genetic information is used correctly in cells.

Science and Engineering Practices (SEP): Developing and Using Models

Scientists build models to represent the complex steps of transcription. These models help visualize how RNA polymerase interacts with DNA, how base pairing rules apply during RNA synthesis, and how transcription is regulated. You can also use diagrams or simulations to model the transcription process and explore how genes are turned "on" or "off" in different cell types.

Activity Ideas:

DNA to RNA Model – Build a hands-on model using colored beads or paper strips to show how DNA is transcribed into RNA.
Transcription Animation Creation – Use drawing apps, slides, or stop-motion animation to illustrate the steps of transcription on your own.
Gene Regulation Worksheet – Complete a worksheet or interactive quiz that presents scenarios where transcription is blocked or altered, and explain the outcomes.

Crosscutting Concept (CCC): Structure and Function

The structure of DNA and RNA molecules directly influences how transcription works.

Structure: DNA’s double-helix structure allows one strand to serve as a template.

Function: RNA polymerase reads this template to build a matching RNA strand.

Structure: The promoter region of DNA has a specific sequence that signals RNA polymerase to start transcription.

Function: This ensures that genes are transcribed at the right time and in the right cells.

Procedure

Transcript

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