DNA TRANSCRIPTION AND TRANSLATION

DNA/transcription/translation review.


DNA structure

  1. What carbon is missing oxygen in DNA?

    1. 2’ carbon is missing an oxygen

  2. What are the three parts of a nucleotide

    1. 5-carbon sugar, phosphate group, and a nitrogenous base.

  3. What holds the two strands of DNA together?

    1. Hydrogen bonds

  4. Strands of DNA are going different directions, what is this characteristic called?

    1. antiparallel

  5. What nucleotide does DNA NOT have?

    1.  Uracil

  6. What are the differences between RNA and DNA?

    1. One has uracil the other has thymine, dna is double stranded, rna is single stranded

  7. If a DNA strand is composed of 15% A, how much is C?

    1. 35%

  8. Who discovered the structure of DNA

    1. Watson and crick

  9. What is the shape of DNA?

    1. Double helix

  10. What bond connects the sugar-phosphate backbone of DNA?

    1. Phosphodiester bond

  11. What is attached to the 5’ carbon in a nucleotide?

    1. Phosphate group


DNA Replication

  1. This enzyme cuts the hydrogen bonds holding DNA together

    1. helicase

  2. Pieces of DNA created on the lagging strand.

    1. Okazaki fragments

  3. What direction is a complementary strand of DNA created in?

    1. 3’-5’

  4. What direction does DNA polymerase read a DNA strand?

    1. 5’-3’

  5. Where in a cell does DNA replication take place?

    1.  Nucleus 

    2. mitocondria

  6. When does DNA replication take place?

    1. During the s phase

  7. What enzyme lays down a RNA primer?

primase

  1. A RNA primer signals what enzyme to bind there?

    1. Dna polymerase

  2. What enzyme creates a complementary strand of DNA by reading a template strand of DNA?

    1. Dna polymerase

  3. What enzyme seals all of the gaps in DNA strands after replication?

    1. ligase

  4. What is the name of the strand in DNA replication that is created in one, long continuous strand

    1. Leading strand

  5. What is the region of the DNA that shrinks every time DNA is replicated?

    1. telomeres

  6. What does topoisomerase do?

    1. Relieves tension so that the two dna strands dont coil back up together

  7. What do the single strand binding proteins do?

    1. They keep the dna strands open so replication can happen smoothly



Transcription

  1. Where does transcription take place?

    1. neuclus

  2. What does the m in mRNA stand for?

    1. messenger

  3. What enzyme creates a complementary strand of mRNA

    1. Rna polymerase

  4. What direction is mRNA created in?

    1. 5’ - 3’

  5. What is a name of the strand that is not read by RNA polymerase

    1. Coding strand

  6. What is the name of the strand of DNA that is read to make a mRNA strand

    1. Template strand

  7. What is added to the 5’ end of pre-mRNA?

    1. 5’ cap

  8. Where does mRNA processing take place

    1. neucleus

  9. What is the name of the section of pre-mRNA that is cut out in RNA processing?

    1. introns

  10. What nucleotide is added to the 3’ end of mRNA in RNA processing

    1. Poly-A tail

  11. What is the region of DNA called that RNA polymerase binds to in order to start transcription?

    1. Promoter region

  12. What is the region of DNA called that RNA polymerase lets go of at the End transcription?

    1. terminator

  13. Why does transcription have to take place? (i.e. why can’t DNA be used to make proteins?)

    1. Dna is the main source of genetic information


Translation

  1. Where does Translation take place?

    1. ribosomes

  2. What molecule brings amino acids to the ribosome?

    1. trna

  3. What is the nucleotide sequence for the start codon?

    1. AUG

  4. What is the name of the site where amino acids are linked together?

    1. P site

  5. What is the name of the site where amino acids enter the ribosome?

    1. A site

  6. What is the name of the site where amino acids exit the ribosome?

    1. E site

  7. Translation ends once a ______ codon is reached

    1. End

  8. What is the name of the part of tRNA that matches up with the codon?

    1. anticodon

  9. What does translation create?

    1. proteins

  10. What bond connects amino acids?

    1. Peptide bond


Mutation

  1. What is a silent mutation?

    1. Where the codon may change but the same amino acid is produced

  2. What is a nonsense mutation?

    1. Changed a noraml codon into a stop codon

  3. What is a point mutation

    1. Involves a single nucleotide change

  4. What is a frameshift mutation?

    1. Insertion or deletion of neuclotodides that is not a multiple of 3

  5. What is a missense mutation?

    1. Changes one codon which makes it a different amino acid

  6. What can cause a mutation?

    1. Errors in dna replication

  7. What type of mutation causes the most harm?

    1. Frameshoft changes the entire sequence all the way through



DNA/transcription/translation review QUIZ STYLE

DNA/Transcription/Translation Complete Review



DNA Structure

  • What carbon is missing oxygen in DNA? 2' carbon (that's why it's deoxy-ribose)

  • Three parts of a nucleotide: 5-carbon sugar, phosphate group, nitrogenous base

  • What is NOT part of a nucleotide? Amino group (that's in amino acids, not nucleotides)

  • What is NOT a characteristic of DNA? Composed of nucleic acids and lipids (DNA is nucleic acid only, no lipids)

  • What holds DNA strands together? Hydrogen bonds (between base pairs) - NOT ester bonds, phosphodiester bonds, or love!

  • What holds the sugar-phosphate backbone together? Phosphodiester bonds (within each strand)

  • Heat and DNA: As temperature increases, hydrogen bonds break and DNA denatures (double-stranded → single-stranded)

  • Strands going different directions: Antiparallel (one 5'→3', other 3'→5')

  • Significance of 3' and 5' ends: They refer to the orientation of the sugar-phosphate backbone and dictate the direction of replication

  • Nucleotide DNA does NOT have: Uracil (has Thymine instead)

  • RNA vs DNA similarities: Both have the same PURINE bases (A and G)

  • RNA vs DNA differences: RNA has uracil (DNA has thymine), RNA is single-stranded (DNA is double-stranded), RNA has ribose (DNA has deoxyribose)

  • Base pairing rules: A pairs with T, G pairs with C (Chargaff's rules)

  • FALSE statement about bases: Guanine does NOT pair with thymine (G pairs with C!)

  • If DNA is 15% A, how much C? 35% (A=T=15%, so G=C=35%)

  • If DNA is 30% A, how much C? 20% (A=T=30%, so G=C=20%)

  • Constant ratio in DNA: A + G = T + C (purines = pyrimidines) - NOT A + T = G + C

  • Valid base composition example: 5% A, 45% G, 45% C, 5% T (A=T and G=C)

  • Complementary strand example: Template 3'-AGGGCTA-5' → New strand 5'-TCCCGAT-3' (antiparallel and complementary)

  • Who discovered DNA structure? Watson and Crick (with Rosalind Franklin's data)

  • Who did NOT discover DNA structure? Gregor Mendel (he studied genetics/inheritance, not DNA structure)

  • Shape of DNA: Double helix

  • Bond in sugar-phosphate backbone: Phosphodiester bond

  • What's attached to 5' carbon? Phosphate group

  • How is genetic information encoded? Through the sequence of nucleotides (not amino acids, methyl groups, or hydrogen bonds)



DNA Replication

  • Cuts hydrogen bonds: Helicase

  • If helicase is inhibited: The replication fork could not open (replication stops immediately)

  • Reads DNA and creates complementary strand: DNA polymerase

  • If primase is non-functional: DNA polymerase could not begin synthesis (no primers to start from)

  • Pieces on lagging strand: Okazaki fragments

  • Lagging strand characteristics: Created in segments (Okazaki fragments), built 5'→3' but overall direction is opposite to helicase movement

  • Leading strand characteristics: Made in one long continuous strand, DNA polymerase moves in same direction as helicase

  • "Glues" DNA segments together: Ligase

  • If ligase works at only 10% efficiency: Lagging strand would have unjoined Okazaki fragments (NOT "DNA would not unwind")

  • Direction DNA is created: 5' → 3' (ALWAYS!)

  • Direction DNA polymerase reads: 3' → 5' (synthesizes 5' → 3')

  • Where replication happens: Nucleus and mitochondria

  • When replication happens: S phase of cell cycle

  • Lays down RNA primer: Primase (complementary to DNA strand)

  • RNA primer signals which enzyme: DNA polymerase

  • What happens to RNA primers? They are removed and replaced with DNA by DNA polymerase (usually DNA polymerase I)

  • Creates complementary DNA strand: DNA polymerase

  • Seals gaps after replication: Ligase

  • Continuous strand: Leading strand

  • Region that shrinks each replication: Telomeres

  • Telomere function: Prevent the loss of essential genetic information as DNA shortens with each replication (protective caps)

  • Topoisomerase function: Relieves tension/prevents supercoiling

  • Single-strand binding proteins (SSBs): Keep DNA strands separated and stable

  • If SSBs are removed: Separated DNA strands would re-connect prematurely (snap back together)

  • If DNA synthesis suddenly stops then resumes: A checkpoint detected DNA damage and paused replication (quality control mechanism)

  • Breaking phosphodiester bonds: The sugar-phosphate backbone would break apart



Transcription

  • What is transcription? Transcribing DNA into an mRNA message (NOT translating or replicating)

  • Where transcription happens: Nucleus

  • What "m" in mRNA means: Messenger

  • Creates mRNA: RNA polymerase

  • Direction mRNA is created: 5' → 3'

  • Strand NOT read by RNA polymerase: Coding strand (non-template strand)

  • Strand that IS read: Template strand (antisense strand)

  • Where RNA polymerase binds to start: Promoter region (NOT at RNA primer)

  • Added to 5' end of pre-mRNA: 5' cap

  • Where mRNA processing happens: Nucleus

  • Section cut out in processing: Introns (exons are kept)

  • Added to 3' end: Poly-A tail (adenine nucleotides)

  • Where RNA polymerase releases at end: Terminator

  • Why transcription is necessary: Protects DNA (master copy), DNA can't leave nucleus, allows amplification, enables regulation



Translation

  • Where translation happens: At ribosomes (in the cytoplasm) - NOT in the nucleus

  • Brings amino acids to ribosome: tRNA (transfer RNA)

  • Start codon sequence: AUG (required to BEGIN translation)

  • Stop codons: UAA, UAG, UGA (signal END of translation)

  • Site where amino acids are linked: P site (Peptidyl site)

  • Site where amino acids enter: A site (Aminoacyl site)

  • Site where tRNA exits: E site (Exit site)

  • Site that holds the growing polypeptide chain: P site (Peptidyl site)

  • Part of tRNA matching codon: Anticodon (located on tRNA)

  • Direction ribosome moves along mRNA: 5' to 3'

  • Translation stages in order: Initiation → Elongation → Termination (NOT Initiation → Termination → Elongation)

  • What determines amino acid added: The mRNA codon sequence

  • How many nucleotides in one codon: Three (3)

  • Translation creates: Proteins (polypeptides)

  • Bond connecting amino acids: Peptide bond

  • Primary function of translation: Converting RNA to protein

  • NOT involved in translation: DNA polymerase (that's for replication, not translation)

  • Required to BEGIN translation: Start codon (AUG) - NOT RNA primer



Translation Practice - Genetic Code

  • Example 1: 5'-AUGCCUGAUUGCUAA-3'
    AUG = Met, CCU = Pro, GAU = Asp, UGC = Cys, UAA = STOP
    Answer: Met-Pro-Asp-Cys-STOP

  • Example 2: 5'-CGAAUGAGUGAUUGCUAA-3'
    Start at AUG: AUG = Met, GAG = Glu, UGA = STOP
    Answer: Met-Glu-STOP (CGA is before start codon, so ignored)



Mutations

  • Silent mutation: Codon changes but same amino acid produced (no effect)

  • Nonsense mutation: Normal codon → STOP codon (premature termination)

  • Point mutation: Single nucleotide change (substitution)

  • Frameshift mutation: Insertion/deletion NOT a multiple of 3 (shifts reading frame)

  • Missense mutation: Codon changes → different amino acid

  • What causes mutations: Errors in DNA replication, mutagens (chemicals), radiation, viruses

  • Most harmful mutation type: Frameshift (changes entire sequence downstream)



Quick Memory Tricks

  • Base pairing: A-T, G-C (DNA) / A-U, G-C (RNA)

  • Same in DNA and RNA: Purines (A and G) are the same in both

  • Bonds: Hydrogen bonds hold base pairs together; Phosphodiester bonds hold backbone together

  • Replication enzymes: Help Please, Don't Leave (Helicase, Primase, DNA polymerase, Ligase)

  • Translation stages: I.E.T. (Initiation, Elongation, Termination)

  • Ribosome sites: A-P-E (order tRNA moves through)

  • RNA processing: Introns = INterruptions (cut out), Exons = EXpressed (kept)

  • Synthesis direction: "5 to 3, that's the key!" (all synthesis goes 5' → 3')

  • Deoxy = 2': DNA is missing oxygen on the 2' carbon (deoxy = without oxygen)

  • Chargaff's constant: Purines = Pyrimidines (A + G = T + C)

  • Translation location: Ribosomes in cytoplasm (NOT nucleus)

  • Transcription location: Nucleus (NOT ribosomes)



⚠ CRITICAL Mistakes to Avoid

  • Hydrogen bonds hold BASE PAIRS together; Phosphodiester bonds hold BACKBONE together

  • DNA polymerase reads and creates DNA (replication); NOT involved in translation

  • Translation happens AT RIBOSOMES in cytoplasm, NOT in nucleus

  • RNA polymerase binds to PROMOTER region to START transcription, NOT at RNA primer

  • Ligase seals gaps; if defective, Okazaki fragments stay unjoined (NOT "DNA won't unwind")

  • Translation stages: Initiation → Elongation → Termination (NOT Initiation → Termination → Elongation)

  • DNA polymerase is NOT involved in translation (that's for replication only)

  • Start codon (AUG) is REQUIRED to begin translation, NOT RNA primer

  • DNA synthesis direction is 5' → 3', NOT 3' → 5'

  • The 2' carbon is missing oxygen in DNA, NOT the 5' carbon

  • G pairs with C, NOT with T!

  • Constant ratio: A + G = T + C (purines = pyrimidines), NOT A + T = G + C

  • DNA and RNA have the SAME purines (A, G), but DIFFERENT sugars