module 2 - 3.9 DNA replication and the genetic code Flashcards
what are the 4 requirements for DNA to be a genetic molecule?
- must carry information (this is the genetic code)
- must replicate (this is DNA replication)
- must allow for the information to change (this is mutation)
- must control the phenotype (this is gene expression using protein synthesis)
where is DNA information stored?
in the sequence of nitrogenous bases
the sequence of A, C, T, and G encodes information in the form of what to make what?
encodes information in the form of genes to make proteins
when are most genes only accessible?
when DNA is unwound (chromatin)
why is extreme accuracy of DNA replication necessary?
in order to preserve the integrity of the genome in successive generations
in eukaryotes, when does DNA replication occur?
during the S phase of the cell cycle (stationary phase)
what is the S phase?
when the cell is doing its job
what is the replication rate like in prokaryotes/ eukaryotes?
prokaryotes - faster rate, lower fidelity (accuracy)
eukaryotes - slower rate, higher fidelity (accuracy)
what is semi-conservative DNA replication?
- one strand of a double helix is passed on unchanged to each daughter cell
- ‘conserved’ strand acts as a template for synthesis of a new, complementary strand by DNA POLYMERASE
what is N14?
non-radioactive isotope of nitrogen
what is N15?
radioactive isotope of nitrogen
where does DNA replication begin?
at the origin (methionine)
what is the origin within prokaryotic cells?
single circular DNA molecule or chromosome and so single origin of DNA replication
where is the origin within eukaryotic cells?
eukaryotic cells have multiple, linear DNA molecules/ chromosomes & each DNA molecule has multiple origins of DNA replication
where does DNA replication always go from and to?
5’ to 3’ direction
what does DNA polymerase require before synthesis can be initiated?
a free 3’ hydroxyl group
what is the difference between the old and new DNA strand to do with the way they are read?
the new DNA template strand is read in a 3’ to 5’ direction, whereas the old strand is read from 5’ to 3’ direction