a) Draw the A-T and G-C base pairs. - Label the bases with the one-letter code. – - Number the atoms in the rings and label the atom that attaches to the sugar. - Mark the groups that interact in normal Watson-Crick base-pairing with arrows: use an arrow towards the groups for hydrogen bond acceptors, and use an arrow away from the group for hydrogen bond donors. b) Circle the nitrogen atoms that would be protonated at very low pH (pH 3) that are not protonated at pH 7. c) Will A-T, or G-C base-pairs or both kinds of base-pairs be perturbed at pH 3?
Gene Interactions
When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.
Gene Expression
Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
It is known that double stranded DNA is denatured at low pH. pKa values should
allow the determination of whether this is due to perturbation of the hydrogen bonding in A-T
and/or G-C base pairs. The table gives values for the pKas of different protonated groups in the
nucleobases.
Nucleobase Position & pKa
A N1, 3.5
G N7, 1.6; N1, 9.2
C N3, 4.2
T N3, 9.7
a) Draw the A-T and G-C base pairs.
- Label the bases with the one-letter code. –
- Number the atoms in the rings and label the atom that attaches to the sugar.
- Mark the groups that interact in normal Watson-Crick base-pairing with arrows: use an
arrow towards the groups for hydrogen bond acceptors, and use an arrow away from the
group for hydrogen bond donors.
b) Circle the nitrogen atoms that would be protonated at very low pH (pH 3) that are
not protonated at pH 7.
c) Will A-T, or G-C base-pairs or both kinds of base-pairs be perturbed at pH 3?
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