What is the basic structure of a DNA molecule?
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Mastering this deck will enhance your understanding of DNA's molecular architecture and the mechanisms ensuring accurate genome duplication, which is essential for fields like genetics, biotechnology, and medicine. This knowledge enables you to interpret experimental data, troubleshoot replication issues, and appreciate the molecular basis of inheritance and genetic stability.
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| 1 | What is the basic structure of a DNA molecule? |
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Learn the molecular structure of DNA, its replication process, key enzymes, and regulation mechanisms.
DNA is a double helix composed of two antiparallel strands made up of nucleotide monomers, each consisting of a sugar (deoxyribose), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine). |
| Think of a twisted ladder with rungs of base pairs. |
| 2 | Which nitrogenous bases are classified as purines and which as pyrimidines? | Purines: adenine (A) and guanine (G); Pyrimidines: thymine (T) and cytosine (C). | Purines are larger with two rings; pyrimidines are smaller with one ring. |
| 3 | What is complementary base pairing in DNA? | Adenine pairs with thymine via two hydrogen bonds, and cytosine pairs with guanine via three hydrogen bonds, ensuring accurate copying during replication. | Remember the AT and GC pairs as 'complementary' partners. |
| 4 | What is the role of DNA helicase in replication? | DNA helicase unwinds the DNA double helix by breaking hydrogen bonds between base pairs, creating a replication fork. | Think of helicase as the 'unzipping' enzyme. |
| 5 | What are Okazaki fragments and on which strand do they form? | Okazaki fragments are short DNA sequences synthesized discontinuously on the lagging strand during replication. | They are the 'short pieces' on the lagging strand, assembled in a series. |
| 6 | Which enzyme synthesizes new DNA strands during replication? | DNA polymerase synthesizes new DNA by adding nucleotides in a 5' to 3' direction complementary to the template strand. | Polymerase = builder of new DNA strands. |
| 7 | What is the function of DNA primase in replication? | DNA primase synthesizes a short RNA primer that provides a starting point for DNA polymerase to begin DNA synthesis. | Primase lays down the initial 'starter' RNA segment. |
| 8 | Which enzyme replaces RNA primers with DNA during replication? | DNA polymerase I removes RNA primers and fills in the gaps with DNA nucleotides. | Think of polymerase I as the 'gap filler'. |
| 9 | What is the role of DNA ligase in DNA replication? | DNA ligase seals nicks between Okazaki fragments and joins DNA strands together to form a continuous double helix. | Ligase acts as the 'glue' in DNA synthesis. |
| 10 | What is semi-conservative replication? | Semi-conservative replication is the process where each new DNA molecule consists of one original (template) strand and one newly synthesized strand. | Imagine copying a recipe, keeping one original and making a new one. |
| 11 | Which enzyme is responsible for relieving supercoils ahead of the replication fork? | Topoisomerase alleviates supercoiling by transiently cutting and rejoining DNA strands, preventing tangling. | Topoisomerase manages DNA's 'twist and turn'. |
| 12 | During replication, which strand is synthesized continuously, and which is synthesized discontinuously? | The leading strand is synthesized continuously, while the lagging strand is synthesized in fragments (Okazaki fragments). | Leading = smooth; lagging = in pieces. |
| 13 | What is the function of single-strand binding proteins (SSBs)? | SSBs bind to single-stranded DNA to prevent re-annealing and protect it from nucleases during replication. | Think of SSBs as 'protective coats' for single strands. |
| 14 | What is the origin of replication? | The origin of replication is a specific DNA sequence where replication begins, often rich in A-T pairs for easier unwinding. | It's the 'starting point' for copying DNA. |
| 15 | How does DNA replication differ between prokaryotes and eukaryotes? | Prokaryotic replication is typically bidirectional from a single origin, while eukaryotic chromosomes have multiple origins of replication allowing for faster duplication. | Think of multiple starting points in eukaryotes vs. one in prokaryotes. |
| 16 | What is the significance of telomeres in DNA replication? | Telomeres are repetitive DNA sequences at chromosome ends that protect against loss of genetic information during DNA replication; they shorten with each cell division. | Telomeres act like 'caps' on shoelaces to prevent fraying. |
| 17 | What is the role of origin recognition complex (ORC) in replication? | The ORC is a protein complex that marks the origins of replication and initiates the assembly of the replication machinery. | ORC is like the 'starter kit' for replication. |
| 18 | Name a key enzyme involved in DNA replication that also has proofreading activity. | DNA polymerase has 3' to 5' exonuclease activity, which allows it to proofread and correct mismatched nucleotides during DNA synthesis. | Proofreading DNA polymerase ensures accuracy. |
| 19 | What mechanisms regulate DNA replication initiation in eukaryotic cells? | Regulation involves cell cycle checkpoints, licensing factors, cyclins, and kinases to ensure replication occurs once per cycle and at the correct time. | Think of it as a 'security system' preventing re-replication. |
| 20 | Which process ensures the fidelity of DNA replication? | Proofreading by DNA polymerase, mismatch repair mechanisms, and DNA damage repair pathways ensure high fidelity during replication. | Multiple layers of quality control maintain DNA integrity. |
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