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DNA, RNA & Protein Synthesis in Genetics

Explore the basics of genetic information flow, from DNA to proteins, through transcription and translation processes. Differentiate between DNA and RNA, decode the genetic code, and understand the role of nucleic acids.

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DNA, RNA & Protein Synthesis in Genetics

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  1. DNA, RNA & Protein Synthesis Ribose RNA Hydrogen bonds Mrs. Stewart Biology I Uracil Adenine

  2. Objectives over next few lessons: • Can differentiate between DNA and RNA • Can explain steps of Transcription • Can explain steps of Translation • Can summarize how to get from DNA code to the expression of a trait • Can summarize the relationship between chromosomes, genes and DNA

  3. Face Partners

  4. What is the relationship between chromosomes, DNA and genes • A gene is a section of the DNA sequence that codes for a protein. • Each unique gene has a unique sequence of bases. • This unique sequence of bases will code for the production of a unique protein. • It is these proteins and combination of proteins that determine the phenotypes for our traits.

  5. What is the purpose of the genetic code in DNA? To create proteins

  6. Objective: Be able to explain how we get from DNA code to expression of a trait DNA Gene Trait Protein

  7. Bacon – explain the purpose of the DNA code

  8. Central Dogma • The basic idea of how hereditary information flows from DNA sequence to create functioning proteins

  9. Two Types of Nucleic Acids • DNA – Deoxyribonucleic acid • RNA – Ribonucleic acid • Need both types of nucleic acids to get from the DNA code to producing proteins

  10. RNA DNA Single Stranded & short (one gene) Double Stranded & long (1000s genes) Base Pairs: A-T C-G Base Pairs: A-U C-G Sugar: Ribose Sugar: Deoxyribose

  11. RNA’s JOB = Use DNA code to make proteins!! Differences between DNA and RNA:

  12. Eggs – tell bacon how to differentiate between DNA and RNA

  13. Types of RNA Short single strand that carries a copy of the DNA code for one gene from the nucleus to the ribosome • mRNA – Messenger RNA • rRNA – Ribosomal RNA • tRNA – Transfer RNA Combines with proteins to make the ribosome. Carries amino acids to the ribosome to build a protein chain.

  14. What does every gene “code” for? Proteins

  15. What are the monomers that build proteins? Amino Acids

  16. DNA Structure • To crack the genetic code found in DNA we need to look at the sequence of bases. • The sequence of bases are read in triplets (sets of 3) called codons. A G G - C T C - A A G - T C C - T A G T C C - G A G - T T C - A G G - A T C • Each codon codes for a specific amino acid

  17. Where is the DNA kept inside a cell? Inside the nucleus

  18. Which organelle is the site of protein synthesis? Ribosomes

  19. DNA cannot leave the nucleus, so…

  20. DNA GENE RNA Ribosome Protein Trait

  21. Protein Synthesis Overview There are two steps to making proteins (protein synthesis): 1) Transcription (occurs in the nucleus) DNA RNA 2) Translation (occurs in the cytoplasm) RNA  protein

  22. Protein Synthesis Animation

  23. Adenine (DNA and RNA) Cytosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA Transcription Nucleus

  24. Transcription occurs in three main steps:

  25. Initiation: Transcription begins when the enzyme RNA polymerase binds to the DNA at a promoter site. Promoters are signals in the DNA strand (a certain sequence of bases) that indicate to the enzyme where to bind to make RNA.

  26. Elongation: • The enzyme separates the DNA strands by breaking the hydrogen bonds, and then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA. • RNA polymerase pairs up free floating RNA nucleotides with DNA template and joins the nucleotides together to form the backbone of the new mRNA strand.

  27. Termination When mRNA hits a termination sequence, it separates from the DNA

  28. Making mRNA • RNA polymerase : enzyme that unravels a segment of DNA (gene) and builds a complementary mRNA strand based off DNA template • Example: • DNA strand: A T G G G A A C T T A C • mRNA strand: U A C C C U U G A A T G • After mRNA strand is complete – DNA reforms and mRNA leaves the nucleus and heads to ribosomes

  29. mRNA synthesis animation

  30. Bacon – summarize the process of transcription for eggs

  31. Transcription vs. Replication • The main difference: • Transcription results in one single-stranded mRNA molecule. • Replication results in two double-stranded DNA molecules. Practice • DNA template • DNA Complement (replication) • mRNA (transcription) ATTCGGAGC TAAGCCTCG UAAGCCUCG

  32. Eggs – explain how to tell the difference between replication and transcription

  33. Stop here and practice!!

  34. Bell Work • What is the ultimate purpose of the genetic code in DNA? • How do we “read” that code?

  35. Bell Work • DNA contains the hereditary information for life. Which structure in DNA illustrates where that information is held? B A C D

  36. PROTEIN SYNTHESIS OBJECTIVES Investigate how the genetic code carried on mRNA is translated into a protein Practice “decoding” genetic codes Create unique genetic code to encrypt a secret message STANDARDS • CLE 3210.4.1 Investigate how genetic information is encoded in nucleic acids. • CLE 3210.4.2 Describe the relationships among genes, chromosomes, proteins, and hereditary traits. • 3210.4.1 - Use models of DNA, RNA, and amino acids to explain replication and protein synthesis.

  37. After we transcribe the message so it can leave the nucleus, we then must have a way to “read” the message.

  38. The Genetic Code • The “language” of mRNA instructions is called the genetic code. • This code is written in a language that has only four “letters” (A,G,C,U) • How can a code with just 4 letters carry instructions for 20 different amino acids?

  39. The Genetic Code – what does it code for? • Proteins (polypeptides) - long chains of amino acids that are joined together. • There are 20different amino acids. • The structure and function of proteins are determined by the order (sequence) of the amino acids

  40. The Genetic Code The genetic code is read 3 letters at a time. A codonconsists of three consecutive nucleotides that specify a single amino acid that is to be added to the polypeptide (protein). The four bases (letters) of mRNA (A, U, G, and C) are read three letters at a time (and translated) to determine the order in which amino acids are added to a protein.

  41. The Codon Wheel • 64 different mRNA codons are possible in the genetic code.

  42. More than one codon can code for the same amino acid • Example: GGG, GGU, GGA, GGC = Glycine • Some codons give instructions • Example: AUG = start • Example: UGA, UAA, UAG = Stop

  43. Cracking the Secret Code • To decode a codon: • start at the middle of the circle and move outward. • Ex: CGA = Arginine • Ex: GAU = Aspartic Acid

  44. Cracking the Code • This picture shows the amino acid to which each of the 64 possible codons corresponds. • To decode a codon, start at the middle of the circle and move outward. • Ex: CGA • Arginine • Ex: GAU • Aspartic Acid

  45. Translation Translation takes place on ribosomes, in the cytoplasm or attached to the ER. • rRNA and tRNA will decodethe message on the mRNA strand to produce a polypeptide chain (protein).

  46. Translation animationTranslation animation – mcgraw hill

  47. Messenger RNA (mRNA) The mRNA that was transcribed from DNA during transcription, leaves the cell’s nucleus and enters the cytoplasm.

  48. Transfer RNA (tRNA) Transfer RNA (tRNA) molecules in the cytoplasm will bond with a specific amino acid Then, tRNA carries that amino acidto the ribosome Each tRNA molecule has three unpaired bases called an anticodon. These bases are complementary to one codon on the mRNA strand.

  49. tRNA molecule Anticodon

  50. Translation

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