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DNA and Its Functions

DNA and Its Functions. 3.1 DNA Structure. Double-stranded helical polymer of nucleotides, held together by H-bond between bases A, T, G, C Deoxyribose and phosphate group. Within any DNA molecule, the amount of thymine is always equal to the amount of adenine (same for GC)

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DNA and Its Functions

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  1. DNA and Its Functions

  2. 3.1 DNA Structure Double-stranded helical polymer of nucleotides, held together by H-bond between bases A, T, G, C Deoxyribose and phosphate group

  3. Within any DNA molecule, the amount of thymine is always equal to the amount of adenine (same for GC) These are called complementarypairs

  4. Functions of DNA Replication Protein Synthesis Mutations Recombinant DNa

  5. 3.2 Replication The replication of DNA is required in order for cells to divide Replication occurs during Interphase of mitosis

  6. Three steps The enzyme, DNAhelicase breaks the H-bonds causing it to unzip, exposing the bonding locations of their bases New DNA nucleotides move into the nucleus where DNApolymeraseenzymes ensure they bond onto their exposed complementary bases on the parent strands The Process continues along the length of the parent strands and results in two separate identical DNA molecules each with an original strand and a new strand.

  7. Review Equal amount of A and T in DNA is logical because These molecules bond together DNA is a double stranded helix These molecules are not the same size One is a purine and one is a pyrimidine

  8. Equal amount of A and T in DNA is logical because These molecules bond together DNA is a double stranded helix These molecules are not the same size One is a purine and one is a pyrimidine

  9. DNA molecules from unrelated organisms differ in their Types of sugar Number of strands Sequence of bases Order of phosphates

  10. DNA molecules from unrelated organisms differ in their Types of sugar Number of strands Sequence of bases Order of phosphates

  11. Replication MOST accurately refers to the synthesis of Complementary strands of RNA for mitosis Complementary strands of DNA for mitosis Proteins based on the sequence of bases in RNA Proteins based on the sequence of bases in DNA

  12. Replication MOST accurately refers to the synthesis of Complementary strands of RNA for mitosis Complementary strands of DNA for mitosis Proteins based on the sequence of bases in RNA Proteins based on the sequence of bases in DNA

  13. A polymer of nucleic acid is found in the cytoplasm of a living animal cell. Which of the following is MOST likely true about this molecule? Helical Contains ribose Double stranded Contains thymine

  14. A polymer of nucleic acid is found in the cytoplasm of a living animal cell. Which of the following is MOST likely true about this molecule? Helical Contains ribose Double stranded Contains thymine

  15. Which of the following is true for any given strand of DNA? [A] = [C], [T] = [G] [A] = [G], [T] = [C] [A] + [T] = [G] + [C] [A] + [G] = [T] + [C]

  16. Which of the following is true for any given strand of DNA? [A] = [C], [T] = [G] [A] = [G], [T] = [C] [A] + [T] = [G] + [C] [A] + [G] = [T] + [C]

  17. 3.3 Protein Synthesis • Another function of DNA is the assembly of amino acids into proteins at the ribosomes • The ribosomes can either be • embedded in the walls of the RER, usually following the secretory pathway and are exported via exocytosis • located free In the cytoplasm if it is to be used within the cell

  18. A gene functions to directly make messenger RNA (mRNA)

  19. To start, the DNA in the region of the gene “puffs up” by breaking the H-bonds between base pairs The beginning point for the synthesis of mRNA is marked by the sequence of nucleotide TAC (bases) on DNA This process is called transcription

  20. Once constructed, mRNA leaves the nucleus and becomes associated with a ribosome where the protein will actually be formed Each set of 3 nucleotides from an mRNA strand functions as a codon, which gives 64 different combinations These triplets determine which of the 20 amino acids is to be delivered to the ribosome

  21. Translationis the second phase of protein synthesis and it occurs at the ribosomes • mRNA arrives at ribomose where ribosomal RNA (rRNA) helps align it into the correct position on the ribosome with AUG (methionine) as the start codon for building a protein

  22. Transfer RNA (tRNA) molecules, with anticodons complementary to the mRNA codons, transport specific amino acids into place at the ribosomes Incoming amino acids are linked by the formation of peptide bonds to the growing polypeptide

  23. Once tRNA is free of its amino acid, it leaves the ribosome to bond onto another amino acid of the correct type in the cytoplasm The process continues until a terminator codon is reached (tRNA that does not carry an amino acid)

  24. Review The cellular flow of inherited information is from Protein to RNA to DNA DNA to RNA to Protein DNA to Protein to RNA RNA to DNA to Protein

  25. The cellular flow of inherited information is from Protein to RNA to DNA DNA to RNA to Protein DNA to Protein to RNA RNA to DNA to Protein

  26. When using the Genetic Code to determine the aa sequence in a peptide, one must use the Code sequence from DNA Codon sequence from mRNA Anticodon sequence from tRNA Base sequence from the amino acids

  27. When using the Genetic Code to determine the aa sequence in a peptide, one must use the Code sequence from DNA Codon sequence from mRNA Anticodon sequence from tRNA Base sequence from the amino acids

  28. What is the compliment of a DNA strand with AAGCTT? UUCGAA TTCGAA AACGTT TTCGUU

  29. What is the compliment of a DNA strand with AAGCTT? UUCGAA TTCGAA AACGTT TTCGUU

  30. When the genetic message ATC in DNA causes the synthesis of mRNA with UAG, an amino acid will be delivered to a ribosome by a tRNA molecule bearing TUC AUG AUC ATC

  31. When the genetic message ATC in DNA causes the synthesis of mRNA with UAG, an amino acid will be delivered to a ribosome by a tRNA molecule bearing TUC AUG AUC ATC

  32. Which of the following is NOT true about the Genetic Code? It contains start and stop codons It is different in different types of cells It has 64 different possibilities of base sequences It is composed of a triplet code of three bases per codon

  33. Which of the following is NOT true about the Genetic Code? It contains start and stop codons It is different in different types of cells It has 64 different possibilities of base sequences It is composed of a triplet code of three bases per codon

  34. 3.4 Mutations A gene (point) mutation is an error made during one of the processes that involve base pairing between nucleotides Chromosome mutations involve segments of chromosomes or entire chromosomes during cell division as in the case of trisomy 21 (down syndrome)

  35. Mutations commonly result from a factor from the environment called a mutagen Radiation and chemicals are the two most common mutagens Three types of mutations: deletion, addition, substitution

  36. Deletion A single nucleotide gets left out Gene of daughter strand is one nucleotide short During transcription, the set of triplets from this point on would be incorrect

  37. Addition Nucleotide is inserted along normal DNA strand Also incorrect from this point on in the daughter strand Protein produced is often non functional Cells often die under this mutation, especially if protein was supposed to be essential enzyme

  38. Substitution Everything is correct, except one nucleotide replaces another The mRNA strand produced will contain all the right codons except the one that has been substituted This MAY affect the incorporation of the correct amino acid into the protein

  39. If a substitution does not change the outcome of the protein produced, then it is degenerative If the substitution did change the protein (different amino acid), it may never function properly All proteins are intended for some purpose; mutant proteins may reach their appropriate destination, but fail to function properly

  40. 3.5 Recombinant DNA Recombinant DNA technology allows scientists to insert segments of DNA from one organism into the chromosomes of another E. coli is a relatively common and harmless human bacterium that is easy to maintain in vitro (in the lab) and it will undergo binary fission about every 20 minutes under good conditions.

  41. Advantages Producing insulin, growth hormones, interferon (cancer treatment), etc Certain strains that help environment (oil-metabolizing bacteria) Production of genetic clones to study differential gene expression

  42. Minimize the effects of genetic errors in humansby removing, repairing and reinserting the gene Production of hybrid species of some food crops that are disease resistant or more tolerant of extreme environmental conditions

  43. Review If the normal nucleotide sequence was TACGGCATG, what type of gene mutation is present if the resulting sequence becomes TAGGCATG? Deletion Addition Substitution chromosomal

  44. If the normal nucleotide sequence was TACGGCATG, what type of gene mutation is present if the resulting sequence becomes TAGGCATG? Deletion Addition Substitution chromosomal

  45. Which of the following is NOT a result of addition or deletion of the nucleotide sequence CATUAUCCC? ATUAUCCC CTUAUCCC CATUAUCGC CATTUAUCCC

  46. Which of the following is NOT a result of addition or deletion of the nucleotide sequence CATUAUCCC? ATUAUCCC CTUAUCCC CATUAUCGC CATTUAUCCC

  47. The sequence of nucleotides in DNA that codes for the polypeptide sequence Phe-Leu-Ile-Val is TTG-CTA-CAG-TAG AAA-AAT-ATA-ACA AUG-CTG-CAG-TAT AAA-GAA-TAA-CAA

  48. The sequence of nucleotides in DNA that codes for the polypeptide sequence Phe-Leu-Ile-Val is TTG-CTA-CAG-TAG AAA-AAT-ATA-ACA AUG-CTG-CAG-TAT AAA-GAA-TAA-CAA

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