Chapter 16 (DNA Replication) Flashcards
What are the monomers of lipids?
FAG: Fatty Acids linked toGlycerol (For fats, oils, phospholipids)
What kind of rxn is DNA replication?
➡️ synthesis rxn➡️ Anabolic➡️ requires energy
what is a special characteristic of DNA replication?
semi-conservative (one old strand and one new)
When does DNA replication happen?
S phase
Replication bubble: (2)
↔️ Bidirectional (bubble)✂️ 2 replication fork moves in opposite directions (daughter strands) [Image]
in which direction is DNAsynthesized?
5’ ➡️ 3’ (for RNA as well!)
What does primer (RNA) do?
provides 3’OH that allows DNA replication‼️ very important
What do we call the replication towards the fork?
Leading strand ➡️ continuous
What do we call the replication away from the fork?
Lagging strand ➡️ Discontinuous, Okazaki fragments
Steps of DNA replication in order (6)
- Helicase (unzips DNA by breaking H bonds) + Topoisomerase (avoids the supercoiling tendency)2. SSDNA binding proteins (sticks to the parental strand to prevent tendency of DNA to rezip)3. Primate (RNA primer) ➡️ 3’OH that allows DNA replication4. DNA polymerase III (adds DNA in 5’ ➡️ 3’) + proofreading makes sure no mistake in replication⭐️ for lagging strand the steps 3 & 4 are repeated with RNA primer being placed closer to the fork each time ➡️ forms Okazaki fragments5. DNA polymerase I (chews on RNA primer and replaces it w/ DNA)6. Ligase (glues the Okazaki fragments of the lagging strand together to from continuous strand)
When does DNA replication happen in eukaryotic and prokaryotic cells?
Eukaryotic ➡️ S phaseProkaryotic ➡️ Continuously
How many replication origins do each type of cells have?
Eukaryotic ➡️ Multiple origins per linear chromosomeProkaryotic ➡️ Single origin per circular chromosome [Image]
What problem do we encounter in eukaryotic cells when replicating DNA?
the linear ends of chromosomes gets shorter after replication
Whats the solution to the replication problem for eukaryotic cells?
telomeres
Whats the problem with DNA replication in prokaryotic cells?
improper separation of replicated chromosomes
Do we have a solution for dna replication problem in prokaryotic cells?
No :(
What are telomeres?
- non-coding repeats of hexanucleotide (AGGGTT) at both ends of linear chromosomes2. enzyme: telomerase adds telomere sequences
Whats the role of telomeres?
protect chromosomes from damage and loss of genetic information
Which cells maintain telomerase (4) and which ones don’t (1)?
✅ cancer, germ, stem, embryonic cells❌ somatic cells
What does an absence of telomerase lead to?
shortening of telomeres
Which cells are shortening associated with?
aging cells
What does the hayflick limit state?
When a chromosomes reach a critical short length the cell stops dividing
true or false: Cancer cells have high telomerase activity
True, that’s why they can divide infinitely, telomeres don’t get shorter
How many telomere do we find in one linear chromosome?
1 DNA w/ 2 telomeres
How many telomeres do we find in one metaphase chromosome?
4 telomeres BECAUSE• Each chromosome = 2 sister chromatids (2 DNA molecules).• Each chromatid has 2 telomeres, so there are 4 telomeres per chromosome. [Image]
Haploid vs Diploid in meiosis and mitosis
[Image] [Image] [Image] [Image]
Where does the energy for DNA polymerization come from?
✅ From nucleoside triphosphates (dNTPs)• Two phosphates break off, releasing energy to add the nucleotide. [Image]
True or false : DNA polymerase forms phosphodiester bonds between complementary base pairs
False!➡️ Hydrogen bonds hold complementary base pairs together (A-T, C-G).
