When a DNA molecule is in water, each base pair releases a pair of hydrogen ions. As a result, the DNA molecule has a net charge. Since there are a lot of base pairs in a string of DNA, this can be a lot of charge! On the web, find a reliable site (and say why you think it is reliable) that tells you the number of base pairs in a typical human chromosome. (Not the Y chromosome!) To get a sense of the total amount of charge involved, imagine that you had two coiled up chromosomes, each with a charge of 2 extra electrons per base pair. Suppose you held them fixed in a vacuum one micrometer apart. For simplicity, model the chromosomes as point charges. Estimate the electric force that the two chromosomes exert on each other in this situation. Explain why this kind of electrostatic repulsion is not a problem when DNA is in its natural environment. You may take the Coulomb constant to be kC ~ 9 x 109 N-m2 /C2
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.
When a DNA molecule is in water, each base pair releases a pair of hydrogen ions. As a result,
the DNA molecule has a net charge. Since there are a lot of base pairs in a string of DNA, this
can be a lot of charge!
On the web, find a reliable site (and say why you think it is reliable) that tells you the number of
base pairs in a typical human chromosome. (Not the Y chromosome!) To get a sense of the total
amount of charge involved, imagine that you had two coiled up chromosomes, each with a
charge of 2 extra electrons per base pair. Suppose you held them fixed in a vacuum one
micrometer apart. For simplicity, model the chromosomes as point charges.
Estimate the electric force that the two chromosomes exert on each other in this situation.
Explain why this kind of electrostatic repulsion is not a problem when DNA is in its natural
environment.
You may take the Coulomb constant to be kC ~ 9 x 109 N-m2
/C2
.
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