Exam 2 - Chapter 7 Flashcards
Genome
Complete set of genetic information
- chromosome plus plasmids
mRNA
Messenger RNA
rRNA
Ribosomal RNA
tRNA
Transfer RNA
Replisomes
Assembly line of DNA replication
Leading Strands
Synthesized continuously in the 5’ to 3’ direction
Lagging Strands
Synthesized discontinuously in the 5’ to 3’ direction
DNA Gyrase
Enzyme that temporarily breaks the strands of DNA, relieving the tension caused by unwinding the two strands of the DNA helix
DNA Ligase
Enzyme that joins two DNA fragments together by forming a covalent bond between the sugar and phosphate residues of adjacent nucleotides
DNA Polymerases
Enzymes that synthesize DNA; they use one strand of DNA to make the other complementary strand. Nucleotides can only be added to the 3’ end of an existing fragment-therefore, synthesis always occurs in the 5’ to 3’ direction
Helicases
Enzymes that unwind the DNA helix at the replication fork
Origin of Replication
Distinct region of a DNA molecule at which replication is initiated
Primase
Enzyme that synthesizes small fragments of RNA to serve as primers for DNA synthesis
Primer
Fragment of nucleic acid to which DNA polymerase can add nucleotides (the enzyme can add nucleotides only to existing fragments)
Replisome
The complex of enzymes and other proteins that synthesize DNA
Okazaki Fragments
Nucleic acid fragment produced during discontinuous synthesis of the lagging strand of DNA
1st Step of DNA Replication
Helicases unzip the DNA helix at the replication forks, revealing two strands that will act as templates
2nd Step of DNA Replication
Synthesis happens continuously at the leading strand, nice and easy
3rd Step of DNA Replication
Synthesis happens discontinuously at the lagging strand, because it can’t add nucleotides to the 5’ end. So it basically has to redo itself with a new RNA primer every time, making okazaki fragments
4th Step of DNA Replication
DNA polymerase adds nucleotides to the 3’ end of okazaki fragments, eventually running into the 5’ end. So it has to replace the RNA primers with deoxynucleotides (no oxygen)
5th Step of DNA Replication
DNA ligase fills the gaps between okazaki fragments with covalent bonds
(-) Strand
Strand of DNA that serves as the template for RNA synthesis; the resulting RNA molecule is complementary to this strand
(+) Strand
Strand of DNA complementary to the (-) strand that serves as the template for RNA synthesis; the nucleotide sequence of the RNA molecule is the same as this strand, except it has Uracil instead of Thymine
Promoter
Nucelotide sequence to which RNA polymerase binds to initiate transcription