ch 34 Flashcards
💔 Previously on Biochem Bachelor… DNA and RNA got down and dirty with their sugar-phosphate drama, double helix hookups, and histone fashion. But now, it’s replication time, and the stakes are higher: who’s the real parent? Who’s the imposter strand? (23 cards)
The Central Dogma: Still the showrunner.
DNA whispers its secrets to RNA.
RNA runs to the ribosome and spills the tea—translating it into protein.
The Paternity Test Drama: Meselson & Stahl Style
Scene: Scientists tag DNA strands like a reality show cast—lightweight ¹⁴N and heavyweight ¹⁵N—and then spin them around (literally, in a centrifuge).
💥 Result? Semiconservative replication wins!
Each new DNA baby gets one strand from the original parent and one hot new strand from the latest season.
💃 DNA Replication: The Split, the Copy, the Drama
DNA doesn’t just replicate—it rips itself apart, but keeps it classy.
Helicase – the messy bestie who unzips the double helix and lets everything out.
SSB proteins – the ones who hold things together and say “stay in your lane.”
Topoisomerase – the calm friend who prevents the group from spiraling (literally stops overwinding).
🔗 Polymerase: The Clingy One with Trust Issues
Needs a primer to even start typing.
Can only add to the 3’ end—never the 5’, never starts anything on its own.
Comes with proofreading skills, making sure every date (base) is the perfect match.
Drops the β and γ phosphates like they’re hot 💅—only keeps the α for the long haul.
Leading Strand: The Golden Child
Follows the rules.
Synthesizes smoothly, continuously, and always knows where it’s going.
Lagging Strand: The Chaotic Younger Sibling
Can’t get it together.
Builds in fragments (called Okazaki pieces) and needs ligase to stitch it all up—like a messy patchwork relationship.
The DNA Replication Rules (aka Drama Club Guidelines)
🧬 Can’t start without a primer.
➕ Can only add onto the 3’ end.
✂ RNA primers eventually get replaced (by polymerase I) and stitched up (by ligase).
😱 Without telomeres, chromosomes lose bits every time—aging is just DNA forgetting its makeup routine.
Crisis Alert: Telomeres on the Edge
Every time DNA replicates, it loses a bit of its ends—like hair breakage from too much drama.
Telomerase comes in with its hair serum, fixing things up and keeping that genetic length luscious. 👑
The Secret Weapon: Proofreading & Repair
If DNA makes a mistake?
Polymerase goes “wait—nope”, slides that incorrect base out of the spotlight, and replaces it.
Because this DNA diva only accepts perfect matches.
Villains of the Episode:
Cisplatin – sneaks in, locks up the DNA, ruins its shape so bad it can’t even function. A total saboteur.
PBD – intercalates like that shady friend who gets between everyone and stirs the pot.
What’s the scandal behind DNA replication?
: It’s semiconservative! Every new DNA strand is half-original, half-fresh drama
Which enzyme unzips the double helix like a messy breakup?
Helicase it rips the strands apart and spills all the secrets.
Why can’t DNA polymerase go solo?
It needs a primer to get started and can only add to the 3 end such high-maintenance energy
What’s the deal with leading vs. lagging strands?
Leading = smooth queen, continuous. Lagging = chaotic Okazaki queen, stitched together in
pieces.
Who plays matchmaker in DNA base pairing?
DNA polymerase checks each new base and throws shade at mismatches with exonuclease
action
Whos the saboteur of DNA structure?
Cisplatin crashes the double helix party and blocks repair like a toxic ex.
What enzyme stitches together Okazaki fragments?
DNA ligase the glam spot welder tying up all the loose ends
What protects chromosome ends from falling apart?
Telomeres rich in guanine and full of loop-de-loop drama to stay safe from nucleases.
What causes chromosomes to shrink over time?
Loss of bases at the 5 end during replication DNAs version of split ends
How do polymerases keep replication accurate?
With proofreading they catch typos like a grammar-obsessed editor.
Why can’t replication happen without all 4 dNTPs?
Miss one? No show. DNA refuses to work with an incomplete cast
What gets released when a base joins the chain?
Pyrophosphate (PPi) drama leftovers from the bonding scene.
