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Protein Synthesis

Protein Synthesis. RNA Structure and Function. The double helix structure of DNA explains how DNA is stored The next few days we will talk about how the information in DNA will become an expressed gene This process of information to expression is what gives organisms their traits.

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Protein Synthesis

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  1. Protein Synthesis

  2. RNA Structure and Function • The double helix structure of DNA explains how DNA is stored • The next few days we will talk about how the information in DNA will become an expressed gene • This process of information to expression is what gives organisms their traits

  3. RNA Structure and Function • The first step in decoding the information in genes is to copy a DNA sequence to RNA • RNA molecules carry out the process of making proteins

  4. RNA Structure and Function • RNA has a structure that is similar to the structure of DNA • RNA – Ribonucleic acid • The RNA nucleotide is similar to DNA but does not exclude an oxygen on the second carbon

  5. RNA Structure and Function • Another key difference is that RNA is single stranded • It forms a single helix instead of a double helix • This means that all of RNA’s bases are unpaired when RNA is by itself

  6. RNA Structure and Function • A third major difference is the base pairing rules that are true for RNA • RNA substitutes the nitrogen base uracil for thymine • Uracil is a nitrogen base that falls into the pyrimidine family

  7. RNA Structure and Function • JUST TO REVIEW! • RNA forms nucleotides that are slightly different from DNA • RNA is a single helix • RNA substitutes Uracil for Thymine

  8. Types of RNA • There are three main types of RNA • mRNA • tRNA • rRNA • They each have a different and specific function when it comes to making proteins • Many of these types of RNA will be edited and changed throughout their lifetime • DNA is not edited or changed

  9. Types of RNA • Messenger RNA or mRNA carries copies of the DNA • mRNA is the messenger between the DNA (recipe) and the ribosomes (kitchen) • It starts in the nucleus but leaves to go to the ribosomes • If RNA is damaged or changed, we can always make more

  10. Types of RNA • Ribosomes are made of two different subunits that fix together • Each subunit is made up of many proteins and ribosomal RNA or rRNA • This makes the ribosome the perfect place for translation

  11. Types of RNA • Transfer RNA or tRNA is molecule that carries amino acids to where they are assembled into proteins • They also have a RNA codon that allows them to figure out where to go • This codon is a three nucleotide base sequence that allows the tRNA to know where to drop off its amino acid

  12. Protein Synthesis • We have learned that DNA holds the information needed to turn genotypes into phenotypes • Now we need to learn the process of going from “A”s, “G”s, “C”s and “T”s into physical things that can be seen

  13. Protein Synthesis • Protein synthesis is the process of going from a section of DNA to a protein • DNA codes for different proteins that can be used by the body to perform cellular processes

  14. Protein Synthesis • Protein synthesis is made up of two different processes • Transcription is the process of going from DNA to mRNA • Translation is the process of going from mRNA to a fully formed protein

  15. Transcription Begins • Transcription is happening at all times on DNA • It starts at an area of the DNA called a promoter • A promoter is a section of DNA that allows enzymes to attach and begin transcription

  16. Transcription Begins • At the promoter an enzyme called RNA Polymerase attaches and begins to perform transcription • RNA polymerase is an enzyme with three main functions • Binds to DNA • Separates DNA strands • Creates complementary RNA strand

  17. The Process • Once RNA polymerase attaches to DNA it unzips a small section of DNA and creates a small section of RNA • The RNA is created by creating a complementary strand of RNA from the unzipped DNA • This is similar to DNA replication, however we are making RNA

  18. The Process • This continues until RNA polymerase hits a terminator • A terminator is a section of DNA that lets the RNA polymerase know when to stop transcribing

  19. The Process • The resulting polymer is not quite mRNA yet • This RNA is almost ready to leave the nucleus and begin translation • Before it can leave the nucleus it has to be edited for the benefit of the cell

  20. Video • http://www.youtube.com/watch?v=ztPkv7wc3yUhttp://www.youtube.com/watch?v=5MfSYnItYvg

  21. mRNA Editing • Once the RNA is done being copied it has to be edited • This allows the cell to cut out sections that are not needed and keep sections that are important • This process is called RNA splicing

  22. mRNA Editing • When it edits RNA the sections that are kept are called exons (expressed sequences) and the sections that are thrown out are called introns (intervening sequences) • This gives RNA the ability to be changed

  23. mRNA Editing • The resulting polymer made from exons is “capped” and is called mRNA • This mRNA is free to leave the nucleus and begin translation

  24. Translation • The process of taking a completed mRNA information and creating proteins is called translation • This is because you are translating the message of RNA to a sequence of amino acids • Translation has three main phases • Initiation • Elongation • Termination

  25. Translation • The process of translation happens in a ribosome • In the ribosome the mRNA brings instructions in the form of nucleotides • tRNA brings amino acids and drops them off in specific locations

  26. Translation • During translation mRNA is “read” in codons • Codons are sections of three nucleotides that are in mRNA • Codons allow tRNA to know where to drop off their amino acid

  27. Initiation • Initiation begins when a strip of mRNA reaches a ribosome • The mRNA binds to the small subunit of a ribosome • The specific orientation of the mRNA and rRNA allows the rest of the steps to happen

  28. Initiation • mRNA begins to be “read” at the start codon • This is a very specific set of three nucleotides that will allow more amino acids to be attached after the start codon • They always code for the amino acid methionine

  29. Elongation • The process of elongation happens after initiation • Elongation is when amino acids are fixed together by the ribosome and a long string of amino acids (a polypeptide) is created • In elongation amino acids are added to the existing methionine

  30. Elongation • The amino acids are formed however, they have to be formed very specifically • This is why the ribosome has two different sites for the creating of polypeptides • The P site will hold the growing polypeptide • The A site will is used to hold the next tRNA that is going to drop off an amino acid

  31. Elongation • During elongation a tRNA with an amino acid is brought to the A site while the T site is filled • A peptide bond is formed between the amino acids • Then the T site is vacated and the tRNA from the A site is transferred to the T site

  32. Termination • This process continues until there is a stop codon that stops elongation • Like there is only one start codon, there is only three stop codons • The stop codon does not actually code for an amino acid

  33. Termination • After the stop codon the tRNA is released into the cytoplasm • The ribosome is now free to get a new piece of mRNA and start all over again

  34. Video • http://www.youtube.com/watch?v=5bLEDd-PSTQ-PSTQ

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