DNA and Genetics

1. Describe the DNA structure: polymer of 2 polynucleotide chains that coil around each other to form a double helix 2. What is the func- - it carries the genetic instructions for the development, tion of DNA? functioning, growth + reproduction of all known organism + many viruses 3. What are nucleotides composed of? - nitrogenous base - pentose sugar - phosphate group 4. What are the 2 DNA strands held together by? strong covalent bonds formed between the deoxyribose sugar of 1 nucleotide + phosphate of the next nucleotide 5. What bonds hydrogen bonds hold nitrogenous bases together? 6. Why are the - the sugar-phosphate backbone twists around itself in a DNA strands are coil anti-parallel? - the twisting protects the bases inside it + prevents them from being damaged by the environment 7. What was Rosalin Franklin's image of X-ray diffraction + also on the the double-helix complementary base pairing in DNA model of DNA structure based on? 8. What does a a pyrimidine base purine base pair to? 9. What is a purine double ring base base? 10. What is a pyrimi- single ring base dine base? 1/9 11. What are the 2 types of purine base? adenine guanine 12. What are the 2 types of pyrimidine base? cytosine thymine 13. How many hydro- 3 gen bonds do CG pairs have? 14. Which pair of CG bonds, as they have 3 H bonds + so more energy is bases is stronger required to denature them and why? 15. What is erwin chargaff's rule? the percentages of A& T and C&G are always equal 16. What is chromatin? the complex of genomic DNA with proteins called histones 17. What do histones support chromatin's structure do? 18. What are chromosomes? thread-like structures located inside the nucleus of eukaryotic cells 19. What is each chromosome made of? protein + a single molecule of DNA 20. What does a cen- - divides the chromosome into 2 sections tromere do? - hold sister chromatids together in mitosis + meiosis - point of attachment of the spindle 21. What is the pur- to package huge amounts of DNA into the restricted nupose of chromo- cleus somes? 2/9 22. What are telomeres? regions of short repetitive DNA at the ends of chromosomes, which protect the ends from shortening 23. What telomeres linked with? ageing + cancer protection 24. What is a gene? section of DNA that provides the instructions for 1 protein molecule 25. What is mitosis? where the cell divides its DNA + cytoplasm, forming 2 new cells 26. What is G0? resting state where the cell performs its functions + is not preparing to divide 27. What is DNA replication? the biological process of producing 2 identical replicas of DNA from 1 original DNA molecule 28. Why is DNA replication important? - to make new copies of chromosomes for cell division - to help maintain continuity of genetic info - continuous surveillance of DNA + its repair 29. What are the - original DNA template requirements for - free DNA nucleotides DNA replication? - replication enzymes - primers to start the process 30. What are the 3 main steps in replication? - inititation - elongation - termination 31. What must hap- DNA must be unzipped pen before replication can occur? 32. breakage of weak hydrogen bonds 3/9 How is the double helix unwound? 33. What is DNA heli- enzyme that unzips DNA case? 34. When the DNA A Y shape, known as the replication fork strands seperate, what shape does it form? 35. What is attached a phosphate group to the 5' end strand? 36. What is attached a hydroxyl group to the 3' end strand? 37. What is 5' and 3' leading strand, is continuously synthesised by DNA polyend also known merase as? 38. What is 3' to 5' end also known as? lagging strand, discontinuous 39. How is an RNA primer is extended by DNA polymerase okazaki fragment formed? 40. What does DNA helicase do? unwinds + separates double strand DNA, forms the replication fork by breaking H bonds between nucleotide pairs 41. What does DNA primase do synthesises RNA primers that act as templates for the starting point of DNA replication 42. What does DNA polymerase do? 4/9 synthesises new DNA molecules by adding nucleotides to leading + lagging strands (also proofreads new DNA strands) 43. What does topoi- unwinds + rewinds the DNA strands to prevent the DNA somerase do? from becoming supercoiled 44. What does exonuclease do? group of enzymes that remove nucleotides bases from the end of a DNA chain 45. What does DNA ligase do? facilitates the joining of DNA strands by formation of phospodiesterase bonds 46. How does DNA it excises bases that are mismatched + replaces them with polymerase cor- the correct base rect errors? 47. What is the con- the concept that genetic info flows from DNA to mRNA to cept of the cen- protein tral dogma of molecular biology? 48. Where does in the nucleus trasncription occur? 49. What does tran- a pre-mRNA molecule scription produce? 50. What happens it is processed to produce the mature mRNA, which exits to the pre-mRNA the nucleus + and is translated produced in transcription? 51. Where does translation occur? in the cytoplasm 5/9 52. What are triplets? groups of 3 successive nucleotide bases in DNA 53. What happens the DNA sequence of a gene is rewritten using RNA during transcrip- nucleotides + must go through additional processing steps tion? to become mRNA 54. What happens during translation? the sequence of nucleotides in the mRNA is translated into a sequence of amino acids in a polypeptide 55. What is the genetic code? the set of rules by living cells to translate info encoded within genetic material into proteins 56. What is a codon? a group of 3 nucleotides ( most codons specify an amino acid) 57. Describe initia- - transcription factor IID (TFIID) binds to the TATA box via tion of transcrip- the TATA box via the TATA-binding protein (TBP) tion - 5 more transcription factors & RNA polymerase combine around TATA box to form a transcription-initiation complex - this resulting complex is bound by RNA polymerase 58. What is the elon- the addition of nucleotides to the mRNA strand gation of transcription? 59. Describe the elongation of transcription: - nucleotides are added to mRNA strand (added at the 3' end) - RNA polymerase moves along the DNA template from 3' to 5' ( using complementary base) 60. Describe termi- the polymerase stops transcription at the end of the termination in trannator + mRNA can be translated without further modificascription in bac- tion teria: 61. mRNA needs to be modified before translation take place 6/9 Describe termination in transcription in eukaroytes: 62. Define translation: RNA to protein 63. What is the start AUG (MET/methionine) codon? 64. Describe initiation of translation: 1) assembly of the components of the translation system occurs 2) the components come together with an mRNA 3) tRNA carrying the first A.A binds to the start codon 65. What does catalyses the bonding between specific tRNAs and the aminoacyl tRNA A.A synthetase do? 66. What does pep- connects A site + P site by forming a peptide during tidyl transferase elongation phase do? 67. What are the components of the translation system? - 2 ribosomal units (60S + 40S) - mRNA template - aminoacyl tRNA synthetase - peptidyl transferase - initiation factors - AUG start codon - stop codon - GTP as an energy source 68. Describe elonga- A.As are brought to the mRNA by tRNAs and are added tion in translato a growing polypeptide chain tion: 69. Describe termi- 1) a stop codon in the mRNA is recognised by a protein nation in transla- release factor tion: 7/9 2) the translational apparatus comes apart, releasing a completed polypeptide 70. How are mRNA codons read? from 5' to 3' 71. What do mRNA order of amino acids in a protein from N-terminus to C-tercodons specify? minus 72. Describe the difference between prokaryotic and eukaryotic mRNA in translation: prokaryotic = Shine-Dalgarno sequence for ribosome binding eukaryotic = 5' cap and poly-A tail for protection + ribosome binding 73. What is help recruits the ribosome to the mRNA by aligning the the Shine-Dalger- ribosome with the start codon no sequence? 74. What is the formyl methionine first prokaryotic amino acid? 75. What is the first methionine eukaryotic amino acid? 76. What are mutations? permanent alteration in a DNA sequence that are propagated through cellular generations 77. What are somatic occur in somatic cells + only affect the individual in which mutations? the mutation arises 78. What are germline mutations? alter gametes + passed on to the next generation 79. What is a misa change in 1 DNA base pair that results in the substitution sense mutation? of 1 A.A for another in the protein 8/9 80. Describe the ef- this may have no effect/ non-functional protein fect of a missense mutation: 81. What is a nona premature stop codon in transcribed mRNA, which resense mutation? sults in an incomplete + usually nonfunctional protein 82. What is the effect protein may not function properly of insertion mutation? 83. What is the effect may alter the function of the resulting protein of deletion mutation? 84. What is a when the addition / loss of DNA bases changes a gene's frameshift muta- reading frame tion? 85. What are - insertions the types of - deletions frameshift muta- - duplications tion? 86. What are the types of DNA damage? - single-base alteration - 2-base alteration - chain breaks - cross-linkage 9/9