When different strains of bacterium infect the same host, how do the strain interact?
Some benign, other virulent, others transformed
Does the transformation factor consist of protein, RNA or DNA
Different experiments in which all but one of the three factors were digested. Result - DNA
Do viral genes consist of DNA or protein?
Viral genes consist of DNA. Viral coats consist of protein.
Primary structure of DNA? (4)
1. 5' end, 3' end
2. Phosphodiester bonds link nucleotides
3. Nitrogen-containing bases project from the backbone
4. Sugar-phosphate backbone of DNA strand
DNA replication is guided by....
Complementary pairing of bases (A with T, C with G) guides the replication of DNA.
DNA replication occurs at multiple points in the ....
(only one in prokaryotes)
DNA Synthesis differs between...
The leading and lagging strands.
(lagging strands - Okazaki fragments which need to be spliced together by ligase)
Synthesis of Leading Strand Steps (4)
1. DNA is unwound & opened by Topoisomerase and Helicase
2. Single-strand binding proteins (SSBP's) stabilize single strands
3. Primase lays down an RNA primer
4. DNA Polymerase III synthesizes DNA in 5' to 3' direction
Enzymes of Leading Strand Replication (5)
topoisomerase, helicase, SSBP's, Primase, DNA Polymerase II
Synthesis of Lagging Strand Steps
1. Primase synthesis RNA primer
2. DNA Polymerase II and Primase work together to make first one, then another Okazaki Fragment
3. DNA Polymerase I removes RNA Primer and replaces DNA
4. DNA Ligase closes gap in the sugar-phosphate backbone
Enzymes of Lagging Strand Steps (8)
Helicase, SSBP, Topoisomerase, Primase, DNA Polymerase II, Primase, DNA Polymerase I, DNA Ligase
Makes RNA primer (leading strand)
Makes RNA primer on an Okazaki fragment (lagging)
What's the dilemma of replicating chromosome ends?
No way to replace RNA primer at the 5' ends of DNA in somatic cells
What results in the shortening of DNA in telomere (end) regions?
The inability of most somatic cells to replace RNA primer at the 5' ends of DNA
Telomere replication steps (5)
1. When the RNA primer is removed from the 5' end of the lagging strand, a strand of DNA remains unreplicated
2. Telomerase binds to the overhanging section of ss DNA.
3. Telomerase adds nucleotides to the end of the parent DNA, extending it
4. Telomerase moves down the DNA strand and adds additional repeats
5. Primase, DNA polymerase, and ligase then synthesize the lagging strand in the 5' - 3' direction, restoring the original length of the chromosome
tars in smoke that damage DNA
Harmless chemical, but converted to potent mutagen by body's own attempt to eliminate BPs