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The Making of a Protein!

The Making of a Protein!. Transcription. DNA holds the instructions. When proteins are produced in the body, the instructions for how to make it comes from the DNA (deoxyribonucleic acid) BUT, there are many steps between a strand of DNA and a protein. Let’s review DNA first.

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The Making of a Protein!

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  1. The Making of a Protein! Transcription

  2. DNA holds the instructions • When proteins are produced in the body, the instructions for how to make it comes from the DNA (deoxyribonucleic acid) • BUT, there are many steps between a strand of DNA and a protein

  3. Let’s review DNA first • DNA is double-stranded • Adenine is always across from Thymine • Cytosine is always across from Guanine • bases are held across from each other by weak hydrogen bonds A--T C--G

  4. Making Proteins • Making proteins involves another step as you saw on the first slide • First, a molecule called RNA is produced • This process is called TRANSCRIPTION

  5. RNA • Ribonucleic acid • single stranded • also made of nucleotides

  6. The nucleotides of RNA • They are slightly different than DNA • They have a sugar and a phosphate group like DNA does

  7. The difference • Three of the nitrogenous bases are the same: • Adenine (A) • Cytosine (C) • Guanine (G) • The last one is different: • Uracil (U)

  8. Instructions for a Protein • The instructions to make a certain protein are coded by the sequence of nucleotides in a strand of DNA (a gene) • These instructions get transferred from the DNA strand to an RNA strand through transcription

  9. So how does this happen? • There are a number of steps in the process of making a protein • The first involves two different parts: • RNA polymerase • the gene’s promoter • A promoter is a certain order of DNA that acts as a “start” signal for transcription

  10. RNA polymerase • RNA polymerase is an enzyme • It binds to the promoter of a gene • This enzyme helps unwind and separate the two strands of DNA

  11. The template • One strand of the DNA acts as a “template” for making the RNA • This means that the nucleotides that will form the RNA pair up with this strand • RNA polymerase helps make this happen

  12. Base Pairing Rules • Just like with DNA, the nucleotides only pair with certain other nucleotides • If there is a Thymine on the DNA strand, Adenine still pairs with it • If there is an Adenine on the DNA strand, it now pairs with Uracil • Cytosine pairs with Guanine just like before

  13. Some covalent bonds are involved • As the RNA nucleotides get added to the strand of RNA that is forming, they are forming covalent bonds • The covalent bonds occur between the nucleotides of the RNA

  14. How it ends • Transcription keeps going until RNA polymerase reaches a “stop” signal on the DNA • RNA polymerase falls off of the DNA and releases the RNA molecule • The DNA then winds back up

  15. Animations: • http://www.dnalc.org/resources/3d/12-transcription-basic.html • http://www.youtube.com/watch?v=OtYz_3rkvPk • Textbook: http://bcs.whfreeman.com/thelifewire/content/chp12/1202001.html • Nebraska: http://croptechnology.unl.edu/animation/transcription.swf

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