DNA Replication Flashcards
DNA replication is _______
Semiconservative
DNA is shaped like a ____ _____ (twisted ladder)
double helix
The backbone of the two strands of the ladder contain?
Sugar and phosphate groups
Rungs of the ladder contain?
Nitrogenous Bases
The “rungs” of the ladder are connected as ____ ____ between the nitrogenous base of one strand and the nitrogenous base of the other strand
base pairs
DNA Base Pairs:
The bases are connected by?
hydrogen bonds
What are the four base pairs of DNA?
-Adenine (A)
-Thymine (T)
-Guanine (G)
-Cytosine (C)
Adenine and Thymine are formed by ___ hydrogen bonds?
2
Guanine and Cytosine are formed by ___ hydrogen bonds
3
One end of each chain the 5 carbon with the phosphate group is “closed”
5’ end
One end of each chain the 3 carbon with an -OH group is “open”
3’ end
DNA:
Strands run in opposite directions
antiparallel
Original Strand
5’ ATCGCTG 3’
Complimentary strand?
3’ TAGCGAC 5’
Crick’s Central Dogma:
Genetic information is stored in ______ and transferred to _______
DNA, Protein
Crick’s Central Dogma:
Transfer of information to proteins is _______
irreversible
Watson & Crick Replication:
The ______ unwinds
helix
Watson & Crick Replication:
Both strands are intact
parental strands
Watson & Crick Replication:
Each parent strand serves as a template for a new ____ _____
daughter strand
Watson & Crick Replication:
Daughter strands are generated by ______ ______ ______ to the parental strand
complementary base pairing
DNA Replication: Prokaryote
-One piece of circular DNA
-4.6 million base pairs
-Copied in as little as 20 minutes
E.coli
DNA Replication: Eukaryote
-46 chromosomes
-6.4 billion base pairs
-copied in a few hours
Homo sapiens (humans)
DNA Replication 3 basic steps?
-Initiation
-Elongation
-Termination
DNA Replication Steps:
-Proteins bind to a specific location
-origin of replication
-Requires single stranded DNA
Initiation
-Unwinds the helix at the replication fork
-Necessary to generate the single-stranded template strands
Helicase
-Binds and stabilizes the single-stranded templates
-Prevents helix from rewinding
Single-Strand Binding Proteins (SSBP)
-Causes single-strand breaks that allow the DNA to unwind and relieve the supercoil strain
-The breaks are resealed before replication
-Relaxes supercoils
Topoisomerase
DNA Replication Steps:
DNA polymerase binds the nucleotide to the 3’ end of the daughter strand
Elongating
Add nucleotides only into -OH of a free 3’ end; ______ onto to the 5’ end
NEVER
If there is no available free 3’ end, then complementary nucleotide _______ is generated
primer
Primer is a short piece of ______ with a free -OH at the 3’ end
RNA
RNA primers are needed to initiate ______ new DNA strands
all
Priming DNA Synthesis:
Synthesized by ____
Primase
RNA Primase doesn’t need a _____ to start
3’ end
Linear DNA elongates in the ___ —> _____ direction only
5’ —> 3’
Direction of synthesis is _____ the fork and _____ from the origin
toward, away
-Short discontinuous fragments
-Each fragment needs a separate RNA primer
-The primer is eventually removed, and new DNA fills the space
Okazaki Fragments
DNA strands synthesized discontinuously are called?
lagging strands
Replication errors are
Mutations
can recognize and replace an incorrect nucleotide as it synthesize the daughter strand
DNA polymerase III
Continuously synthesized strand
Leading strand
The enzyme that removes RNA primers and fills in the gaps with DNA is called
DNA Polymerase I
Enzyme that seals the gaps between Okazaki fragments on the lagging strand is called
DNA ligase
Leading strand direction
5’ —->3’
Lagging strand direction
3’ —-> 5’
Synthesizes RNA primers with a 3’ end for a new strand
Primase
Okazaki strands go in what direction
5’ –> 3’
-Adds nucleotides to the 3’ end of the daughter strand
-Proof reads and repairs mismatched DNA
DNA polymerase
Joins DNA fragments together by forming bonds, seals
Ligase
