1 Testing for purines ultimately would it be possible to det

1) Testing for purines: ultimately, would it be possible to determine if you extracted DNA from strawberry ?Explain the answer.

2) DNA extraction: soduim chloride helps to seperate DNA from its histones. Based on this information and explanation about the structure of DNA, what can be concluded about the charge of histones?

Solution

1) A technique known as DNA barcoding can be used to identify the species by looking at the DNA sequence. This method uses a short genetic marker in the DNA of a species to identify it as belonging to a particular species. A desirable locus or region in a DNA to be used for barcoding should have the following desirable criteria:

For plants, the concatenation of the rbcL and matK chloroplast genes are generally used for DNA barcoding. Maturase K (matK) is a plant plastidial gene. Ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) is an enzyme involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is converted by plants and other photosynthetic organisms to energy-rich molecules such as glucose.

2) Since, each nucleotide of the DNA molecule possesses a negatively charged phosphate group, DNA is a negatively charged molecule. DNA molecules are thus not attracted to each other but are repelled. Adding sodium chloride to a solution containing DNA neutralizes the negative charges of the DNA molecule. Sodium ions create a temporary attraction between sodium and the DNA backbone. The DNA is temporarily neutralized and then easily disassociated from water. NaCl is able to do this because the sodium and chloride ions separate in solution and the positive sodium ions (Na+) are attracted to the negative charges of the DNA’s phosphate groups.

Based on the above we can conclude that the charge on the histone proteins should be positive because negative DNA strands wound around the histone proteins and this will only be possible if the charges are opposite.