Guanine-- -- --Cytosine
Cytosine-- -- --Guanine
*Note: The number of "--" indicates the number of hydrogen bonds between each nitrogenous base pair.
Antiparallel sugar-phosphate backbone
The each sugar-phosphate backbone of DNA is antiparallel with respect to the other.
DNA backbone composition and linkages
Sugar and phosphate compose the backbone of DNA. They are linked together by phosphodiester linkages.
Semiconservative model of DNA
Recombinant or semiconservative DNA is formed when two parental strands split and joins two new strands. So each of the two daughter strands of DNA includes one parental strand and one new strand.
Origins of replication
Eukaryotic DNA: There are multiple orginins of replication sites.
Prokaryotic DNA: Single origin of replicatoin.
The point in which DNA Helicase unwinds the two strands of DNA.
The two parental strands that are broken apart by DNA Helicase and are used as templates to make complementary strands of new DNA ultimately forming two daughter strands.
enzymes that unwind the double helix forming the replications forks and seperating the parental strands -- template strands are formed.
Enzymes that unwind the double helix forming the replication forks and seperating the two parental strands into template strands.
Single Strand Binding Proteins
bind to unpaired DNA strands to prevent them from rejoining.
Breaks, swivles, and rejoins parental DNA because the strain of helicase unwinding can cause damage to the strand.
catalyzes synthesis of new DNA by adding nucleotides to a preexisting chain. Requires a primer that is synthesized by primase. The DNA Polymerase also requires a template strand so that it can synthesize a complementary strand that will bind accordingly.
DNA replicatoin for the leading strand is continuous. DNA Polymerase travels in the 3'---->5' direction on the template strand thus forming a complementry strand that is in the 5'------>3' direction.
DNA replicatoin is fragmented on the lagging strand. Because the lagging strand travels in the 3'------>5' direction on the template strand and forms the complementry strand in the 5'-------->3' direction, primers must be added between fragments.
The fragments of complementry strand DNA on the lagging strand.
Joins the Okazaki fragments together so that one complete complementry strand is formed.
Other enzymes remove/replace incorrectly paired nucleotides that stem form replication errors.
A DNA-cutting enzyme that cuts out damaged or mismatched nucleotide sequences. The gap that gets cut out is filled with nucleotides using the undamaged strand as a template so that a complementry strand can be formed. An example is the nucleotide excision repair (see your text book page 258 for example).