Gene Expression—Transcription How is mRNA synthesized and what message does it carry? Why?

Gene Expression—Transcription How is mRNA synthesized and what message does it carry? Why? DNA is often referred to as a genetic blueprint. In the same way that blueprints contain the instructions for construction of a building, the DNA found inside the nuclei of cells contains the instructions for assembling a living organism. The DNA blueprint carries its instructions in the form of genes. In most cases the genes direct the production of a polypeptide, from which other more complex proteins, such as enzymes or hormones, may be constructed. These polypeptides and other molecules run the organism’s metabolism and, in multicellular organisms, dictate what each cell’s job is. So, what is the language of these instructions and how are they read and decoded by the cellular organelles? This activity will focus on the decoding of genes in eukaryotes. Model 1 – Transcription Template (reading) strand RNA polymerase and transcription factors A A A A A A C C C C C C C G G G G G G G T U U A A C G G G G A C C A Inside the Nucleus Free RNA Nuclear membrane nucleotides Outside the Nucleus Direction Growing strand of pre-mRNA of synthesis 5´ 3´ 5´ 3´ Chromosome from a nondividing cell U U U U U U U U This study source was downloaded by from CourseH on 04-28-2023 14:31:50 GMT -05:00 2 POGIL™ Activities for AP* Biology 1. Consider the eukaryotic cell in Model 1. a. Where in the cell is the DNA found? b. Where in the cell does transcription take place? 2. Refer to Model 1. a. What polymer is synthesized during transcription? b. What monomers are used to construct this polymer and where are they found? 3. According to Model 1, what enzyme is required for transcription? (Hint: Think about how enzymes are named. What ending is used for enzyme names?) 4. Refer to Model 1. a. What is the base-pair rule for a DNA strand matching an RNA strand? b. Compare this base-pair rule with that of two DNA strands. 5. Which strand of the DNA contains the “blueprint” for the pre-mRNA? 6. Consider Model 1. a. In which direction is the DNA molecule read? b. The DNA strand and pre-mRNA strand are anti-parallel. With this in mind label the 3ʹ and 5ʹ ends of the pre-mRNA strand in Model 1. c. In which direction is the pre-mRNA molecule constructed? 7. Before printing presses were available, books had to be transcribed in order to share the information in them. Consider the defi nition of transcription and explain why the process in Model 1 is described using that word. This study source was downloaded by from CourseH on 04-28-2023 14:31:50 GMT -05:00 Gene Expression—Transcription 3 Read This! In eukaryotes the enzyme RNA polymerase joins with several transcription factor proteins at the promoter, which is a special sequence of base pairs on the DNA template strand that signals the beginning of a gene. The transcription factor proteins, along with the RNA polymerase, is called the transcription initiation complex. This moves along the DNA template strand at about 40 base pairs per second producing pre-mRNA. When the RNA polymerase reaches the terminator sequence of base pairs on the DNA template strand, it completes the production of pre-mRNA and releases it into the nucleoplasm. 8. What parts make up the transcription initiation complex? 9. Where on the DNA strand does the transcription initiation complex form? 10. Nearly all cells in an organism contain identical DNA, and each DNA strand may contain hundreds or thousands of individual genes. Is it likely that a cell would transcribe all the genes withi