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Chapter 9 Summary

Key Takeaways

  • Hereditary Information: DNA is the genetic material responsible for storing and transmitting hereditary information in all living organisms. The structure of DNA is a double helix, composed of two strands of nucleotides twisted around each other, discovered by Watson and Crick with key contributions from Rosalind Franklin and Maurice Wilkins.
  • Nucleotides are the building blocks of DNA: They consist of three parts: a deoxyribose sugar, a phosphate group, and a nitrogenous base (A, T, G, or C).
  • DNA Structure: The two strands of DNA are antiparallel, meaning they run in opposite directions (5′ to 3′ and 3′ to 5′). DNA strands have a sugar-phosphate backbone and are connected by complementary base pairs:
    • Adenine (A) pairs with Thymine (T)
    • Guanine (G) pairs with Cytosine (C)
  • DNA Replication: DNA replication is essential for growth, repair, and reproduction, ensuring the faithful transmission of genetic material. Replication of DNA is semi-conservative, meaning each new DNA molecule consists of one original strand and one newly synthesized strand.
  • Replication Process: Replication occurs during the S phase of the cell cycle, ensuring that each daughter cell receives an identical copy of DNA and begins at specific sites called origins of replication, forming replication bubbles as DNA unwinds. The enzyme DNA polymerase adds complementary nucleotides to the exposed bases of the template strand and forms covalent bonds to build the new DNA strand.

OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Summarize the following content into key takeaways.

 

Flash Cards

Text Description
  1. Nucleotide: Building block of nucleic acids that consists of a sugar, a phosphate group, and a nitrogenous base
  2. Double helix: Spiral structure formed by two strands of DNA twisted around each other
  3. Complementary base pairs: Pairs of nitrogenous bases in DNA or RNA that form hydrogen bonds with each other – A with T (or U in RNA) and C with G
  4. DNA replication: Process by which DNA is copied – occurs during S phase
  5. Semi-conservative: Each of the two new DNA molecules consists of one original (parental) strand and one newly synthesized strand
  6. DNA polymerase: Enzymes that build new DNA strands by adding nucleotides during DNA replication
  7. Origin of replication: Specific sequence in DNA where replication begins
  8. Central dogma: The flow of genetic information in cells (DNA → RNA → Protein)
  9. mRNA: Messenger RNA carries genetic instructions from DNA in the nucleus to the ribosomes in the cytoplasm
  10. rRNA: Ribosomal RNA is a component of ribosomes responsible for protein synthesis
  11. tRNA: Transfer RNA carries amino acids to ribosome and matches amino acids with the appropriate codons on the mRNA during translation
  12. Transcription: Copying a DNA sequence into messenger RNA (mRNA)
  13. RNA polymerase: Enzyme that synthesizes RNA from a DNA template during transcription
  14. Promoter: A DNA sequence where RNA polymerase binds to begin transcription
  15. Terminator: A DNA sequence that signals the end of transcription
  16. Splicing: The process of removing introns from RNA and connecting exons
  17. Exons: Coding sequences in RNA that are kept and expressed as protein
  18. Introns: Non-coding sequences in RNA that are removed during splicing
  19. Capping: The addition of cap to the “head” of mRNA for stability and recognition by ribosomes
  20. Polyadenylation: The addition of a poly-A-tail to mRNA
  21. Poly-A Tail: A string of adenine nucleotides added to the tail of mRNA to protect it from breakdown
  22. Translation: The process by which a ribosome reads mRNA and assembles a protein using amino acids
  23. Genetic code: The set of rules by which the sequence of bases in mRNA is translated into amino acids
  24. Codons: Groups of three mRNA bases that specify a particular amino acid
  25. Start codon: The codon (AUG) signals the start of translation and codes for methionine
  26. Initiation complex: When mRNA, ribosome & tRNA come together to start protein synthesis
  27. Stop codon: Codons that signal the end of translation
  28. Mutations: Random changes in the sequence of bases in DNA or RNA
  29. Mutagens: Agent that causes genetic mutations
  30. Chromosomal alterations: Large-scale changes in chromosome structure, such as deletions, duplications, or rearrangements
  31. Point mutation: A change in a single nucleotide in DNA
  32. Silent mutation: Mutated codon codes for the same amino acid
  33. Missense mutation: Mutated codon codes for a different amino acid
  34. Nonsense mutation: Mutated codon is a premature stop codon
  35. Frameshift mutation: Deletion or insertion of one or more nucleotides, changing the reading frame of the base sequence
  36. Neutral mutations: Mutations with no resulting effect on the organism
  37. Beneficial mutations: Increase an organism’s chances of survival or reproduction (code for new versions of proteins)
  38. Proto-oncogene: Normal gene that helps cells divide, that can become an oncogene if it is mutated
  39. Oncogene: Mutated gene that can cause normal cells to become cancerous by promoting uncontrolled cell growth
  40. Tumour suppressor genes: Genes that slow down or stop cell division
  41. Harmful mutations: Negatively affect an organism’s chances of survival or reproduction and can cause genetic disorders or cancer
  42. Gene expression: The process by which information from a gene is used to make RNA and proteins
  43. Gene regulation: Process by which cells control the expression and timing of genes to produce the right proteins at the right time; controls which genes are “turned on.”
  44. Epigenetic markers: Chemical tags that attach to DNA or histone proteins and regulate gene activity without changing the DNA sequence
  45. Activators: Regulatory proteins that promote transcription by enhancing the interaction of RNA polymerase with the promoter
  46. Repressors: Regulatory proteins that attach to the DNA and prevent transcription by blocking RNA polymerase
  47. Alternative RNA splicing: A process that allows a single gene to produce multiple protein variants by including or excluding different exons
  48. Components of DNA nucleotide: Deoxyribose, a phosphate group, and a nitrogenous base
  49. Nitrogenous bases in DNA: Adenine, guanine, cytosine, and thymine
  50. A pairs with: T
  51. C pairs with: G
  52. What forms the backbone of DNA strands? Sugar-phosphate groups of the connected nucleotides
  53. Enzyme that links nucleotides together in DNA replication? DNA polymerase
  54. How do the instructions in DNA get to the ribosomes outside the nucleus? Transcription makes a copy of the genetic instructions in the form of mRNA, which can pass through pores in the nuclear membrane to the ribosomes in the cytoplasm.
  55. How does RNA differ from DNA? It is single-stranded, contains the sugar ribose (as opposed to deoxyribose) and uses uracil instead of thymine
  56. Three steps in transcription: Initiation, elongation, and termination
  57. What happens in Initiation of Transcription? RNA polymerase binds to the promoter to begin transcription
  58. What happens in Elongation of Transcription? RNA polymerase moves along the template strand of DNA, unwinds the double helix, synthesizes mRNA, and then rewinds the DNA
  59. What happens in Termination of Transcription? RNA polymerase reaches the terminator and detaches from the DNA template
  60. How is mRNA processed? Splicing, capping, and polyadenylation
  61. Three steps in translation: Initiation, elongation, and termination
  62. What happens in Initiation of Translation? Ribosome binds to mRNA; tRNA with the anticodon that matches the start codon brings in the first amino acid (methionine)
  63. What happens in Elongation of Translation? Amino acids are sequentially added to the growing polypeptide chain as tRNAs bring them to the ribosome and match them with the corresponding codons on the mRNA.
  64. What happens in Termination of Translation? Ribosome reaches a stop codon on the mRNA which codes for a release factor. This triggers the end of protein synthesis, so the mRNA, ribosome, tRNA, and newly synthesized polypeptide chain are released
  65. Three main types of mutations? Chromosomal alterations, point mutations, and frameshift mutations
  66. Three types of point mutations? Silent, missense, and nonsense
  67. Are mutations good or bad? Both. Some mutations are harmful and lead to genetic disorders or cancer.  Some mutations are beneficial and produce new version of proteins which help species adapt and change over time. Some mutations are neutral and do not affect the organism.
  68. How do mutations lead to cancer? A series of mutations convert proto-oncogenes into oncogenes to trigger uncontrolled cell growth. Additional mutations inactivate tumour suppressor genes to allow continued growth, which eventually leads to cancer.
  69. How can we have different types of cells in our body, even though they all contain the exact same DNA? We have different cell types because gene regulation controls which genes are turned on or off, leading to differential gene expression. This selective expression allows cells with the same DNA to perform unique functions.
  70. How are genes regulated in eukaryotes? Epigenetic regulation, transcriptional regulation, post-transcriptional regulation, translational regulation, and post-translational regulation

OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Can you give me brief summaries of these key terms?

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Biology Essentials 1 Copyright © 2025 by Kari Moreland is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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