Frederick Griffith studied two strains of Streptococcus pneumoniae, type R bacteria, which does not cause pneumonia and type S bacteria, which does cause pneumonia. Griffith found that heat-killed type S bacteria also does not cause pneumonia; however, when he injected a mouse with both live type R bacteria and heat-killed type S bacteria, the mouse died and live type S bacteria was found in its body. Something in the heat-killed type S bacteria transformed the type R strain into a killer, when previously it had been harmless. Therefore, Griffith determined that an unknown substance transmits a disease-causing trait between two types of bacteria, while Avery, MacLeod, and McCarty’s experiment determined that the “transforming principle” was DNA. Avery, MacLeod, and McCarty’s experiment determined this by treating the type S strain with a protein-destroying enzyme, which showed the protein was not transmitting the killing trait, and then, they treated the S type strain with a DNA-destroying enzyme, which, showed the DNA was the “transforming principle.” …show more content…
The twin rails of the ladder are alternating units of deoxyribose and phosphate joined with covalent bond. The ladder rungs are A -T and G - C base pairs joined by hydrogen bonds.

a. A G G C A T A C C T G A G T C
T C C G T A T G G A C T C A G
b. G T T T A A T G C C C T A C A
C A A A T T A C G G G A T G T From smallest to largest: nitrogenous base → nucleotide → codon → gene → chromosome → genome → nucleus →