DNA Replication Flashcards

Question

What would happen if complementary strands were parallel?

Answer 1

if the complementray stands would align in the same direction (both 5' to 3') the charges of the complementary nucleotides would repel and no hydrogen bonds would form the antiparallel orientation brings the partial charges into alignment to form hydrogen bonds

Answer 2

DNA replication is universal throughout Life’s organisms  Differences in the mechanisms have evolved over time, but the process is universally the same 1. Each strand of the parental DNA molecule remains intact during replication 2. Each parental strand of DNA serves as a template directing the synthesis of a complementary, antiparallel daughter strand 3. Completion of replication results in the formation of 2 identical daughter duplexes, each composed of 1 parental strand and 1 daughter strand

Answer 3

DNA replication is bidirectional, forming a “replication bubble” - Prokaryotes have a single origin of replication- bc their dna is a circle (bacteria_ - Eukaryotes have multiple origins of replication- ours is longer more complex so that’s why we have multiple so everything can be replicated in a timely manner - As DNA unwinds it will synthesize both strands at once BUT one strand is 3’-5’ and one is 5’-3’ so it creates a biredirectional approach that happens simultaneously

Answer 4

``` Helicase DNA topoisomerase Single-stranded binding proteins (SSB) Primase DNA polymerase III DNA polymerase I DNA ligase ```

Answer 5

unwinds the double helix breaks the hydrogen bonds, allowing for the double-stranded DNA to unwind (like a zipper unzips) unwinding of the strands occur ahead of the advancing replication fork

Answer 6

Relaxes supercoiling (When you try to unwind something that’s already tightly wound it winds up more tightly somewhere else so this helps relax it and prevents it from breaking) binds to the DNA and relaxes supercoiling Prevents the DNA from twisting back upon itself Also has ligase function that if DNA breaks it can glue it back up and be ready for more replication

Answer 7

created by primase is 12-24 bp in length (acts as a starting place telling the DNA polymerase to come and attach nucleotides) Made of RNA, complementary to the template DNA strand a short single stranded segment that begins the daughter strand and provides a 3' OH end to which a new DNA nucleotide can be added by DNA polymerase

Answer 8

synthesizes RNA primers binds to the site of initiation and creates a primer (starting point of DNA Replication)

Answer 9

Prevents re-annealing of separated strands Act like a little plug to prevent strands from coming back together because the base pairs will want to complementary base bind to the unwound strands, preventing them from reforming the DNA duplex

Answer 10

Template strand reads 3’->5’ direction The new strand elongates in 5’->3’ direction

Answer 11

removes and replaces RNA primer with DNA removes the RNA nucleotides one-by-one and replaces them with DNA nucleotides that are complementary to the parental strand Begins with the 5’ nucleotide of the RNA primer and progresses in the 3’ direction Uses a 5’->3’ exonuclease(cut out RNA) activity to remove the RNA nucleotides Uses a 5’–> 3’ polymerase(add make more DNA) activity to add DNA nucleotides Continuously pushes the gap in the 3’ direction until there is only a single nucleotide bp gap

Answer 12

synthesizes DNA is an enzyme that adds nucleotides complementary to the template strand. But needs RNA! (brings the DNTPS takes off 2 of the phosphates and attach into sugar phosphate backbone) Template strand reads 3’->5’ direction The new strand elongates in 5’->3’ direction Adds nucleotides to the 3’ end (hydroxyl) of the previous nucleotide The primers provide the initial 3’ OH group for DNA polymerase to add the first nucleotide Nucleotides are complementary to the parental strand

Answer 13

joins DNA segments together (ie “glues”) When we remove primer it'll glue the 3’ hydroxyl end of where the primer was with the nucleotide to the 5’ phosphate group and close up gaps comes in and fills the gap by creating the final phosphodiester bond between the two nucleotides that joins the Okazaki fragments

Answer 14

complex that contains the proteins and enzymes required for replication One at each replication fork One carries out DNA synthesis in the 5’ ->3’ direction continuously following the leading strand The other carries out DNA synthesis discontinuously in the 5’ ->3’ direction, but in the opposite direction of the replication fork on the lagging strand

Answer 15

an enzyme that makes polymers bigger molecules

Answer 16

a region of active dna replication containing replication forks on each end an origin of replication in the middle and leading and lagging strands in each half of the bubble

Answer 17

In DNA replication, the continuously synthesized strand

Answer 18

In DNA replication, the discon- tinuously synthesized strand whose Okazaki fragments are ligated to complete new strand synthesis.

Answer 19

DNA fragments ~ 100 -200 bp long (in Eukaryotes, shorter in prokaryotes), that are later joined together by DNA ligase as DNA polymerase I removes the primers and replaces with nucleotides

Answer 20

the method of dnA replication that synthesizes new DNA in both directions from a replication origin

Answer 21

DNA polymerase I has the ability to “stop” and reverse replication to remove an incorrect nucleotide - Will replace it with the correct one The protein structure of the polymerases resemble a “hand and thumb” Nucleotide errors result in improper hydrogen bonding in the base pairs, resulting the daughter strand being displaced - Blocks the addition of more nucleotides and rotates the strand into the 3’ -to -5’ exonuclease site in the polymerase

Answer 22

Unlike prokaryotes, our DNA is linear within the nucleus Replication of circular DNA creates 2 complete copies of the parental DNA Linear DNA cannot fully replicate and replication falls short Due to RNA primers near the end of the lagging strand This shortens the chromosome after each successive replication Problem is solved in telomeres

Answer 23

Bidirectional expansion is caused by the expanding replication bubble and DNA synthesis at the replication fork

Answer 24

cut out RNA

Answer 25

add make more DNA

Answer 26

RNA primers must be removed before replication is complete Otherwise you have RNA interspersed within your DNA! When DNA polymerase III reaches a primer, it leaves a single stranded gap that must be filled between the nucleotide and the primer

Answer 27

YES Just more prominent on the lagging strand because it has more primers to remove

Answer 28

Replication errors occur ~1 every billion (10 9 ) nucleotides

Answer 29

During replication, the unwinding and creation of the replication fork causes torsional pressure within the parental strands Results in supercoiling, twisting more than just the double helix naturally would Ex. Holding a rubber band stationary on one end, and twisting the other 1. topisomerase cuts one or both DNA strands 2. DNA strands rotate to remove the super coils 3. Topoisomerase rejoins the DNA strands

Answer 30

Non-protein coding (junk DNA, repeating chunkc aaaaaa) Made up of 1000s of 6-12bp repeats, totally 2 to 20kb long at birth Each successive replication shortens the telomeres in somatic cells Contains a knotted fold in the DNA called the T-loop,

Answer 31

protects the telomere from enzymatic degradation by joining with a protein complex called shelterin Early breakdown= early aging and genetic diseases

Answer 32

in Germ-line cells | (enzyme containing RNA) that adds repetitive DNA sequences to the ends of telomeres

Answer 33

number of replication cycles in the cell’s life span (~50-70 cycles)

Answer 34

Unlike prokaryotes, our DNA is linear within the nucleus Replication of circular DNA creates 2 complete copies of the parental DNA Linear DNA cannot fully replicate and replication falls short Due to RNA primers near the end of the lagging strand This shortens the chromosome after each successive replication

Answer 35

Lagging strands are shortened after each replication event when the RNA primer is removed and not replaced with DNA nucleotides Leading strands are synthesised to the ends of linear chromosomes

Answer 36

Causes genomic instability, resulting in increased mutations  Can lead to various cancers  Dyskeratosis congenita -> bone marrow failure  Idiopathic pulmonary fibrosis -> progressive lung disease  Many more... Shortening can also be caused by  Smoking  Stress  Poor overall health (obesity, inflammation)  Chemical exposures, ROS,

Answer 37

site where the double stranded DNA is unwound to create 2 single stranded DNA templates