A Y-shaped region on a replicating DNA molecule where new strands are growing.
the new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' --> 3' direction
a short segment of DNA synthesized away from the replication fork on a template strand during DNA replication, many of which are joined together to make up the lagging strand of newly synthesized DNA, short segment of DNA synthesized discontinuously in small segments in the 3' to 5' direction by DNA polymerase
A short segment of RNA nucleotides that begins, in DNA replication, the leading strand as well as every Okazaki segment on the lagging strand. Enables DNA polymerase to attach DNA nucleotides to the primer.
DNA synthesis takes place during S phase of the cell cycle; the two strands of a DNA double helix separate and each serves as a template for synthesis of complementary daughter strand.
An enzyme that relaxes supercoiling while Helicase continues to open up the DNA molecule during transcription. It cleaves the DNA in half and loops it around to create a negative supercoil.
an enzyme that untwists the double helix at the replication forks, separating the two parental strands and making them available as template strands
single-stranded binding proteins
Protein that binds to single-stranded DNA usually near the replication fork to stabilize the single strands., What binds each strand and keep them from coming back together after helicase unzips the DNA strands?
origin of replication
The specific location on a DNa strand where replication begins.. Prokaryotes typically have a single origin of replication, while eukaryotes have several per chromosome., Site where replication of DNA begins, site where DNA polymerase and other proteins initially bind.
refers to the fact that half of a newly made DNA is the old template.
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of one DNA fragment (such as an Okazaki fragment) to the 5' end of another DNA fragment (such as a growing DNA chain).
a nuclease that releases one nucleotide at a time (serially) beginning at one of a nucleic acid, an enzyme that removes RNA primers from DNA
DNA polymerase I
Enzyme. Removes RNA primers and replaces them with the appropriate nucleotides during DNA replication., removes primer, replaces it with correct nucleotides, proofreads new strand, if errors found exonuclease removes and repairs with correct nucleotides
DNA polymerase III
Enzyme. Responsible for synthesizing complementary strands of DNA during DNA replication., An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain.
principle that bonds in DNA can form only between adenine and thymine and between guanine and cytosine.
relieves "overwinding" strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands
Removes RNA primers in eukaryotes
localization of active replication forks in the cell nucleus. each contains approximately 40 replication forks incorporating nucleotides into DNA strands simultaneously.
A region of DNA controlled by a single origin of replication.
causes of DNA damage
Spontaneous, X-rays, Chemical Carcinogen
nucleotide excision repair
Enzymes detect damaged DNA, nuclease enzymes cut out the damaged area, DNA polymerase adds nucleotides, ligase completes process by closing the break in the sugar-phosphate backbone, The process of removing and then correctly replacing a damaged segment of DNA using the undamaged strand as a guide.
base excision repair
Specific glycosylases recognize and remove damaged bases, AP endonuclease cuts DNA at pyrimidne site, empty sugar is removed and the gap is filled and resealed
enzymes remove and replace incorrectly paired nucleotides that have resulted from replication errors
double-strand break repair
1 - double-stranded breaks are generated by ionizing radiation (X-rays) or oxygen free radicals; 2 - in mammals they are commonly repaired by non-homologous end joining; 3 - during replication, they are repaired by homologous recombination