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Unit 2 genetics nucleic acid rna

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RNA is a single-stranded nucleic acid that plays several roles in protein synthesis. It consists of a phosphate backbone, a ribose sugar, and nitrogenous bases. There are three main types of RNA - mRNA carries copies of DNA instructions to the ribosome, tRNA transports amino acids to the ribosome during protein assembly, and rRNA is a core component of ribosomes. Protein synthesis involves two main stages - transcription of DNA to mRNA in the nucleus, and translation of mRNA to protein by ribosomes in the cytoplasm using tRNA to add amino acids.

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UNIT 2: GENETICS NUCLEIC ACID RNA CAMPBELL & REECE, 2010. CHAPTERS 17,
STRUCTURE OF AN RNA MOLECULE RNA is made up of: Ribose sugar (a pentose sugar with 5 carbons), Phosphate and A nitrogenous base; e.g. Purines (Adenine and Guanine) and Pyrimidines (Cytosine and Uracil). RNA exists largely as single nucleotide chains in living cells.
STRUCTURE OF AN RNA MOLECULE The RNA strand is made up of alternating molecules of ribose sugar and phosphate. The nitrogen bases are attached to the sugar molecules in the strand and stick out laterally as in DNA. A sugar, a nitrogenous base and a phosphate together form a ribonucleotide. An RNA molecule is a polymer of ribonucleotides.
STRUCTURE OF AN RNA MOLECULE Although RNA exists generally as single polynucleotide chain, some segments of RNA molecules may pair temporarily in double- helical form or may fold back on themselves to set up extensive double-helical regions. These fold-back double helices and their arrangement are important to RNA functions.
BASIC STRUCTURE OF AN RNA MOLECULE
RNA STRUCTURAL ELEMENTS
DIFFERENCES BETWEEN DNA & RNA Characters DNA RNA 1 Molecule Double stranded, helical Single stranded, straight or variously folded and twisted. 2 Pentose sugar Deoxyribose Ribose 3 Pyrimidine base Thymine Uracil 4 Complementa ry base pairing Always present and exists between A = T and G = C Normally absent, but may be present in twisted segments of a molecule. If present, pairing is between A = U and G = C 5 Ratio of Purines: Pyrimidines Always 1:1 Not necessarily 1:1
TYPES AND LOCATION OF RNA 1. mRNA (MESSENGER RNA) 2. tRNA (TRANSFER RNA) 3. rRNA (RIBOSOMAL RNA) 4. cRNA (catalyticRNAs) 5. snRNA (Small Nuclear RNA) 6. snoRNA (Small Nucleolar RNA) The blue RNAs are the most important
mRNA Single strand RNA nucleotides. A polynucleotide strand synthesized according to the code of the DNA. It carries the code in base triplet (codon) form, from the DNA to the ribosomes. Found in the nucleus of the cell.
tRNA A single RNA strand folded in the shape of a clover leaf. It carries a specific amino acid on one end and transfers it to the ribosomes. Has an anticodon on the other end; the anticodon base-pairs with a complementary codon on mRNA. Found in the cytoplasm of the cell.
tRNA
rRNA The two ribosomal subunits (large and small) are made of proteins and ribosomal RNA (rRNA) The single-stranded molecule of rRNA is variously folded and twisted upon itself in certain regions forming a secondary structure. Constitutes 50% of a ribosome. Help to bond mRNA to protein of the ribosome. Found in the ribosomes in the cytoplasm of the cell.
rRNA
PROTEIN SYNTHESIS PROTEIN SYNTHESIS CONSIST OF 2 DISTINCT STAGES: TRANSCRIPTION TRANSLATION
TRANSCRIPTION The 3 stages of transcription: (1) Initiation (2) Elongation (3) Termination
TRANSCRIPTION: INITIATION 1. RNA-polymerase attaches to the beginning of the DNA code called the promotor 2. It unwinds the DNA molecule and breaks the weak hydrogen bonds between the complementary strands a bubble forms 3. The one strand now acts as a template for the formation of the mRNA strand.
TRANSCRIPTION: INITIATION
TRANSCRIPTION : ELONGATION 4. Free nucleotides in the nucleus bonds to the complementary bases of the DNA template strand. (Uracil replaces Thymine in mRNA) 5. More free nucleotides bond to their complementary bases, to elongate the mRNA strand, until the entire code has been transcribed. The DNA parts already transcribed rewound.
TRANSCRIPTION : ELONGATION
TRANSCRIPTION : TERMINATION 6. The mRNA will detach from the DNA template. 7. The RNA polymerase detaches and starts all over again at a different location where needed. 8. Now the pre-mRNA strand has to undergo a modification and RNA splicing before it can leave the nucleus.
TRANSCRIPTION : TERMINATION
Unit 2 genetics nucleic acid rna
mRNA modification and splicing Each end of a pre-mRNA molecule is modified in a particular way: 5 end receives a modified nucleotide 5 cap 3 end gets a poly-A tail
mRNA modification and splicing RNA splicing removes introns (non-coding RNA) & joins exons (coding RNA), creating an mRNA molecule with a continuous coding sequence. RNA splicing is carried out by spliceosomes.
Why are these modifications necessary? Seems to facilitate the export of mRNA Protect mRNA from hydrolytic enzymes Help ribosomes attach to 5 end
TRANSLATION oA cell translates an mRNA message into protein oWHAT IS NEEDED TO DO THIS? mRNA (Carries the code) tRNA (pick up amino acid and takes it to the mRNA Amino acid (connect to form protein) Ribosome (Location for protein synthesis)
THE 3 STAGES OF TRANSLATION Initiation Elongation Termination
TRANSLATION: INITIATION 1. Small ribosomal subunit binds with mRNA 2. Small subunit moves along mRNA until it reach the start codon (AUG) 3. The matching anti-codon of the tRNA (with amino acid Methionine)bonds with the start codon. 3. Add the large subunit which completes the translation initiation complex.
TRANSLATION: INITIATION
TRANSLATION: ELONGATION 1. More tRNA anticodons attach to mRNA codons. 2. The amino acids attached to the tRNAs attach to one another by means of peptide bonds. 3. Amino acids form a long polypeptide chain. 4. tRNA releases amino acid to pick up more amino acids
TRANSLATION: ELONGATION
TRANSLATION: TERMINATION Termination occurs when a stop codon in the mRNA reaches the A site of the ribosome The A site accepts a protein called a release factor. The release factor causes the addition of a water molecule instead of an amino acid. This reaction releases the polypeptide, & the translation assembly then comes apart
TRANSLATION: TERMINATION
TRANSLATION: MODIFICATIONS Often translation is not sufficient to make a functional protein Polypeptide chains are modified after translation Completed proteins are targeted to specific sites in the cell
CRACKING THE GENETIC CODE 64 codons have been deciphered. Of the 64 triplets, 61 code for amino acids; 3 triplets are stop signals to end translation. No codon specifies more than one amino acid Genes can be transcribed and translated after being transplanted from one species to another.
CRACKING THE GENETIC CODE (codon)

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Unit 2 genetics nucleic acid rna

  • 1. UNIT 2: GENETICS NUCLEIC ACID RNA CAMPBELL & REECE, 2010. CHAPTERS 17,
  • 2. STRUCTURE OF AN RNA MOLECULE RNA is made up of: Ribose sugar (a pentose sugar with 5 carbons), Phosphate and A nitrogenous base; e.g. Purines (Adenine and Guanine) and Pyrimidines (Cytosine and Uracil). RNA exists largely as single nucleotide chains in living cells.
  • 3. STRUCTURE OF AN RNA MOLECULE The RNA strand is made up of alternating molecules of ribose sugar and phosphate. The nitrogen bases are attached to the sugar molecules in the strand and stick out laterally as in DNA. A sugar, a nitrogenous base and a phosphate together form a ribonucleotide. An RNA molecule is a polymer of ribonucleotides.
  • 4. STRUCTURE OF AN RNA MOLECULE Although RNA exists generally as single polynucleotide chain, some segments of RNA molecules may pair temporarily in double- helical form or may fold back on themselves to set up extensive double-helical regions. These fold-back double helices and their arrangement are important to RNA functions.
  • 5. BASIC STRUCTURE OF AN RNA MOLECULE
  • 7. DIFFERENCES BETWEEN DNA & RNA Characters DNA RNA 1 Molecule Double stranded, helical Single stranded, straight or variously folded and twisted. 2 Pentose sugar Deoxyribose Ribose 3 Pyrimidine base Thymine Uracil 4 Complementa ry base pairing Always present and exists between A = T and G = C Normally absent, but may be present in twisted segments of a molecule. If present, pairing is between A = U and G = C 5 Ratio of Purines: Pyrimidines Always 1:1 Not necessarily 1:1
  • 8. TYPES AND LOCATION OF RNA 1. mRNA (MESSENGER RNA) 2. tRNA (TRANSFER RNA) 3. rRNA (RIBOSOMAL RNA) 4. cRNA (catalyticRNAs) 5. snRNA (Small Nuclear RNA) 6. snoRNA (Small Nucleolar RNA) The blue RNAs are the most important
  • 9. mRNA Single strand RNA nucleotides. A polynucleotide strand synthesized according to the code of the DNA. It carries the code in base triplet (codon) form, from the DNA to the ribosomes. Found in the nucleus of the cell.
  • 10. tRNA A single RNA strand folded in the shape of a clover leaf. It carries a specific amino acid on one end and transfers it to the ribosomes. Has an anticodon on the other end; the anticodon base-pairs with a complementary codon on mRNA. Found in the cytoplasm of the cell.
  • 11. tRNA
  • 12. rRNA The two ribosomal subunits (large and small) are made of proteins and ribosomal RNA (rRNA) The single-stranded molecule of rRNA is variously folded and twisted upon itself in certain regions forming a secondary structure. Constitutes 50% of a ribosome. Help to bond mRNA to protein of the ribosome. Found in the ribosomes in the cytoplasm of the cell.
  • 13. rRNA
  • 14. PROTEIN SYNTHESIS PROTEIN SYNTHESIS CONSIST OF 2 DISTINCT STAGES: TRANSCRIPTION TRANSLATION
  • 15. TRANSCRIPTION The 3 stages of transcription: (1) Initiation (2) Elongation (3) Termination
  • 16. TRANSCRIPTION: INITIATION 1. RNA-polymerase attaches to the beginning of the DNA code called the promotor 2. It unwinds the DNA molecule and breaks the weak hydrogen bonds between the complementary strands a bubble forms 3. The one strand now acts as a template for the formation of the mRNA strand.
  • 18. TRANSCRIPTION : ELONGATION 4. Free nucleotides in the nucleus bonds to the complementary bases of the DNA template strand. (Uracil replaces Thymine in mRNA) 5. More free nucleotides bond to their complementary bases, to elongate the mRNA strand, until the entire code has been transcribed. The DNA parts already transcribed rewound.
  • 20. TRANSCRIPTION : TERMINATION 6. The mRNA will detach from the DNA template. 7. The RNA polymerase detaches and starts all over again at a different location where needed. 8. Now the pre-mRNA strand has to undergo a modification and RNA splicing before it can leave the nucleus.
  • 23. mRNA modification and splicing Each end of a pre-mRNA molecule is modified in a particular way: 5 end receives a modified nucleotide 5 cap 3 end gets a poly-A tail
  • 24. mRNA modification and splicing RNA splicing removes introns (non-coding RNA) & joins exons (coding RNA), creating an mRNA molecule with a continuous coding sequence. RNA splicing is carried out by spliceosomes.
  • 25. Why are these modifications necessary? Seems to facilitate the export of mRNA Protect mRNA from hydrolytic enzymes Help ribosomes attach to 5 end
  • 26. TRANSLATION oA cell translates an mRNA message into protein oWHAT IS NEEDED TO DO THIS? mRNA (Carries the code) tRNA (pick up amino acid and takes it to the mRNA Amino acid (connect to form protein) Ribosome (Location for protein synthesis)
  • 27. THE 3 STAGES OF TRANSLATION Initiation Elongation Termination
  • 28. TRANSLATION: INITIATION 1. Small ribosomal subunit binds with mRNA 2. Small subunit moves along mRNA until it reach the start codon (AUG) 3. The matching anti-codon of the tRNA (with amino acid Methionine)bonds with the start codon. 3. Add the large subunit which completes the translation initiation complex.
  • 30. TRANSLATION: ELONGATION 1. More tRNA anticodons attach to mRNA codons. 2. The amino acids attached to the tRNAs attach to one another by means of peptide bonds. 3. Amino acids form a long polypeptide chain. 4. tRNA releases amino acid to pick up more amino acids
  • 32. TRANSLATION: TERMINATION Termination occurs when a stop codon in the mRNA reaches the A site of the ribosome The A site accepts a protein called a release factor. The release factor causes the addition of a water molecule instead of an amino acid. This reaction releases the polypeptide, & the translation assembly then comes apart
  • 34. TRANSLATION: MODIFICATIONS Often translation is not sufficient to make a functional protein Polypeptide chains are modified after translation Completed proteins are targeted to specific sites in the cell
  • 35. CRACKING THE GENETIC CODE 64 codons have been deciphered. Of the 64 triplets, 61 code for amino acids; 3 triplets are stop signals to end translation. No codon specifies more than one amino acid Genes can be transcribed and translated after being transplanted from one species to another.
  • 36. CRACKING THE GENETIC CODE (codon)