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Transcribing DNA: Replication, Transcription, and Translation

Learn about the processes of DNA replication, transcription, and translation, and understand how genetic information is transcribed and translated into proteins. Explore the role of enzymes and the genetic code.

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Transcribing DNA: Replication, Transcription, and Translation

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  1. Thursday 2/2/17 • AIM: How can we transcribe the DNA code? • DO NOW: 1- Explain the role of enzymes in DNA replication. • 2- Describe DNA Replication • 3- How does DNA Replication create a semi-conservative model?

  2. Replicate the following • GATTACA GATTACA • CTAATGT CTAATCT GATTACA CTAATGT

  3. DNA and RNA are polymers of nucleotides • DNA is a nucleic acid, made of long chains of nucleotides Phosphate group Nitrogenous base Nitrogenous base(A, G, C, or T) Sugar Phosphategroup Nucleotide Thymine (T) Sugar(deoxyribose) DNA nucleotide Figure 10.2A Polynucleotide Sugar-phosphate backbone

  4. Hydrogen bonds between bases hold the strands together: A and T, C and G Hydrogen bond Ribbon model Partial chemical structure Computer model Figure 10.3D

  5. Untwisting and replication of DNA • each strand is a template for a new strand helicase DNA polymerase Figure 10.4B

  6. DNA replication - Genes - the units of inheritance (6/10) - YouTube

  7. DNA replication begins at many specific sites Parental strand Origin of replication Daughter strand Bubble Two daughter DNA molecules Figure 10.5A

  8. 5 end 3 end P • Each strand of the double helix is oriented in the opposite direction P P P P P P P 3 end 5 end Figure 10.5B

  9. 3 DNA polymerasemolecule 5 5 end Daughter strandsynthesizedcontinuously Parental DNA 5 3 Daughter strandsynthesizedin pieces • DNA polymerase works in only one direction 3 P 5 • Telomere sequences are lost with each replication. • Cancer, aging telomeres 5 P 3 DNA ligase Overall direction of replication Figure 10.5C

  10. TRANSCRITION - YouTube

  11. The information constituting an organism’s genotype is carried in its sequence of bases • The DNA is transcribed into RNA, which is translated into the polypeptide DNA TRANSCRIPTION RNA TRANSLATION Protein Figure 10.6A

  12. DNA replicaation: both strands of the double helix act as templates to make new DNA • In transcription only one strand of DNA is the template (the gene)

  13. Transcription produces genetic messages in the form of mRNA RNA nucleotide RNApolymerase Direction oftranscription Templatestrand of DNA Newly made RNA Figure 10.9A

  14. Transcription • The process that builds an RNA molecule from a DNA template • Why does the cell want to build RNA? • To get the genetic code out of the nucleus to the ribosome • WHY? • To build a protein and lead to a physical trait

  15. Transcription cont. • We want to transcribe the gene • Only one strand of the DNA double helix acts as a template and is transcribed • Base Pair Rules • A-U • C-G • Adenine on DNA attracts a Uracil of RNA

  16. Transcribe the following • DNA: AACGGTAGTACGTA • RNA: UUGCCAUCAUGCAU

  17. RNA: ribonucleic acid • Large nucleic acid built from many nucleotides bonded together • Remember a nucleotide consists of a phosphate group, 5 carbon sugar and nitrogen containing base

  18. RNA nucleotide • The 5-Carbon sugar is ribose • The 4 nitrogen containing bases: • Adenine • Uracil • Cytosine • Guanine

  19. 3 types of RNA • mRNA: messenger RNA: carries the genetic code from the nucleus to the ribosome • rRNA: ribosomal RNA: builds ribosomes • tRNA: transfer RNA: carries amino acids to the synthesizing polypeptide

  20. Assessment • DNA: TTGCATGCAATCG • transcribe

  21. FRIDAY 2/3/17 • AIM: How is RNA modified before it leaves the nucleus? • DO NOW: Transcribe the following

  22. Modification of RNA • The rough draft is called the primary transcript • Before it leaves the nucleus it gets modified • Addition of 5’cap and Poly-A tail • The most important is RNA splicing

  23. RNA modification • 5’ cap and Poly A tail protect the RNA from being broken down by cellular enzymes • They also help the ribosome recognize the RNA

  24. RNA splicing • Introns: junk DNA that does not code for proteins • Exons: good DNA codes for protein • Splicesome: enzymes that catalyze the removal of introns and the connection of exons • Allows the human genome to produce a variety of polypeptides • One gene codes for one polypeptide

  25. How do your cells know which amino acids it wants or needs? • ANSWER: the genetic code determines the polypeptide (sequence of amino acids)

  26. Now the mRNA is ready to leave the nucleus and enter the cytoplasm

  27. Quick Review • What are the 3 major events that occur during transcription? • Why is it important to modify the primary RNA before leaving the nucleus?

  28. Monday 2/6/17 • AIM: How is mRNA translated? • DO NOW: 1-How does a cell know which proteins to synthesize? • 2- Why do our cells make proteins? • 3-Explain the importance of messenger RNA. • HOMEWORK: Text read pages 337-338 and page 341 • EXAM THURSDAY

  29. DO NOW ANSWER • 1- The chromosomes which carry genes determine which proteins to make • 2- Our cells make proteins so that they can express physical traits • 3- mRNA: messenger RNA carries the genetic code out of the nucleus into the cytoplasm

  30. The Genetic code • Codon: sequence of 3 nucleotides that specify an amino acid • There are 20 amino acids that build ALL polypeptides • It is the unique sequence of amino acids that build polypeptide chains • It is the unique folding of polypeptides that build proteins • Proteins then lead to physical traits

  31. Codons to know • AUG: start codon. All mRNA start with this codon. It translates to Methionine (Met) • UAA Stop codons • UAG tells translation • UGA to end

  32. An initiation codon marks the start of an mRNA message AUG = methionine Start of genetic message End Figure 10.13A

  33. Translation • There is a specific start AUG codon • There are 3 possible stop codons that terminate UAA,UAG or UGA

  34. 3 types of RNA • mRNA: messenger RNA: carries the genetic code from the nucleus to the ribosome • rRNA: ribosomal RNA: builds ribosomes • tRNA: transfer RNA: carries amino acids to the synthesizing polypeptide

  35. Translation: RNA to amino acid sequence • Involves mRNA, tRNA, rRNA and ribosomes • Before mRNA leaves the nucleus, proteins called splicesomes cut out and paste together coding regions of the primary mRNA transcript • Plays a major role in polypeptide diversity • Now it is ready for translation

  36. mRNA: carries codon message out of the nucleus

  37. tRNA: Transfer RNA carries amino acids to the mRNA-ribosome complex

  38. tRNA anticodon • 3 base pair sequence complementary to the mRNA codon • Anticodon-codon complex allows amino acids to bond in proper sequence

  39. Tuesday 2/7/17 • AIM: How are proteins synthesized? • DO NOW: • DNA: TACGGCCAAGCACGA • cDNA • mRNA • aa • tRNA • HOMEWORK: review book read 114-116. q 1-12 pgs 116-118

  40. Ribosomal RNA builds ribosomes

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