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Transcription DNA g mRNA

Transcription DNA g mRNA. Objectives . Explain the purpose of transcription for a cell Tell how RNA differs from DNA Name the three main types of RNA Describe the process of transcription . Review. What was the purpose for DNA replication?

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Transcription DNA g mRNA

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  1. TranscriptionDNA g mRNA

  2. Objectives • Explain the purpose of transcription for a cell • Tell how RNA differs from DNA • Name the three main types of RNA • Describe the process of transcription

  3. Review • What was the purpose for DNA replication? • So cell division (mitosis & meiosis) can occur and each new cell created has a full set of DNA • What are the Nitrogen bases of DNA? • A, G, C, T • What is the sugar for DNA? • deoxyribose • What does the structure of DNA allow? • The strands are complementary of one another, meaning one strand is a template for the other.

  4. Central Dogma • Soon after there discovery of DNA structure, Watson and Crick, stated that information in molecular biology flows in one direction. From DNA to RNA to proteins. • The central dogma involves three process: • Replication copies DNA • Transcription converts a DNA message into a temporary ‘disposable’ copy of DNA called RNA • Translation interprets an RNA strand into a string of Amino Acids which will turn into specific proteins. Transcription video

  5. What is RNA? 3 main differences between DNA & RNA? RNA is like a “disposable copy” of a segment of DNA. RNA consists of long chains of nucleotides (like DNA) Parts of a Nucleotide: 5 carbon sugar Phosphate group Nitrogenous base RNA sugar- Ribose RNA is single stranded RNA contains Uracil (U) in place of Thymine

  6. Transcription makes 3 types of RNA • Messenger RNA: mRNA • Ribosomal RNA: rRNA • Transfer RNA: tRNA

  7. Function of mRNA • Carries copies of gene instructions for assembling amino acids into proteins from nucleus to ribosome (transcription)

  8. Function of rRNA • Forms part of ribosomes, a cell’s protein factory Large subunit binds to tRNA Binding Sites Small subunit binds to mRNA

  9. Function of tRNA • Brings amino acids from the cytoplasm to a ribosome to help make the growing protein Amino Acid anticodon

  10. Transcription • TRANSCRIPTION :The process of copying a sequence of DNA to produce a complementary (disposable) strand of RNA • During this process, a GENE – not an entire chromosome – is transferred into an mRNA. • The cell needs this process because DNA has the information/code needed to make proteins AND DNA is too valuable to leave the nucleus, so it makes a disposable copy! • THIS IS A MAJOR PART IN PROTEIN SYNTHESIS!!!!!

  11. Overview of Protein Synthesis: • Ribosomes are made in nucleolus • Ribosomes leave through the Nuclear pores on the nuclear membrane • Some attach to ER, while others remain free floating • Ribosomes begin attaching Amino Acids together to form proteins • Proteins enter into RER to be modified and folded (shaped) into structures • Vesicles form from RER and carry proteins to Golgi apparatus • There proteins are • packaged, sorted and/ or • stored in Golgi • Once the proteins are • ready to leave, vesicles • form to transport proteins • throughout the cell and to • other cells.

  12. What are genes? Genes are coded DNA instructions that control the production of proteins within a cell. The code is held with the sequence of nitrogen bases in DNA. Like credit card numbers, unique to every person! REMEMBER: that a chromosome is made up of multiple genes, and transcription only copies specific genes, 1 at a time.

  13. transcription complex start site nucleotides Step 1: • RNA polymerase binds to promoters on DNA strand and begins to unwind a segment of DNA that corresponds to the gene it is copying.

  14. DNA RNA polymerase moves along the DNA Step 2: • RNA polymerase, using only one strand of DNA as a template, adds on free-floating RNA nucleotide • As RNA polymerase moves along the DNA, a growing RNA strands hangs freely as it is transcribed, and the DNA helix zips back together. *A - U, C – G there are NO T’s

  15. Step 3: • Once the entire gene has been transcribed, the RNA strand detaches completely from the DNA. • Exactly how RNA polymerase recognizes the end of a gene is very complicated but we will discuss as it reaching a Stop signal.

  16. RNA polymerase • RNA polymerase is an enzyme that plays multiple roles in transcription process • Unzips the DNA molecule where gene is found • Adds free floating nucleotides to make mRNA strand What it DOESN’T do is proof read it’s work like DNA polymerase.

  17. How does RNA polymerase know where to start and stop? Promoter sites- which have specific nitrogen base sequences (TAC) Promoters are signals in DNA to indicate where an enzyme can bind to make RNA Stop signals/sites – specific sequence of nitrogen bases that tell the RNA polymerase to stop and fall off.

  18. replication transcription one gene growing RNA strands translation DNA

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