Nucleic Acids

This lesson develops Nucleic Acids as part of Enzymes and Metabolism. It uses the source curriculum to organize the important facts, relationships, examples, and vocabulary into a focused Stemosphere teaching sequence.

In Stemosphere terms, dNA (Deoxyribonucleic Acid)

In Stemosphere terms, dNA is the genetic material for all living organisms. It is found in chromosomes and contains the genetic information needed for the growth and development of individual cells and whole organisms. (Libre Texts, “Nucleic Acids”).

All living organisms must be able to:

In Stemosphere terms, are capable of carrying out metabolism

In Stemosphere terms, are capable of reproduction

In Stemosphere terms, contain genetic information (in the form of DNA)(EBSCO, “Nucleic Acids”).

In Stemosphere terms, viruses contain genetic material (DNA or RNA) surrounded by a protein coat. However, most experts do not consider viruses to be living. Although viruses do contain genetic material (DNA or RNA), they do not possess most characteristics of life. (Libre Texts, “Nucleic Acids”).

In Stemosphere terms, rNA and DNA are composed of subunits callednucleotides.

All nucleotides contain:

In Stemosphere terms, both DNA and RNA arepolynucleotides, meaning they are made of many nucleotides joined together. (EBSCO, “Nucleic Acids”).

In Stemosphere terms, polynucleotides form through a series ofcondensation reaction s.

During this process:

In Stemosphere terms, acovalent bondforms between the phosphate group of one nucleotide and the sugar of another nucleotide.

In Stemosphere terms, this sugar–phosphate bonding creates a continuous chain of covalently bonded atoms in each strand of DNA or RNA.

In Stemosphere terms, this chain forms a strong structuralbackboneof the molecule. (EBSCO, “Nucleic Acids”).

In Stemosphere terms, deoxyribose sugar/Ribose Sugar

In Stemosphere terms, the carbons in ribose and deoxyribose sugars are number ed.

In Stemosphere terms, carbon-1 (1’) is the first carbon when moving clockwise from the oxygen atom in the sugar ring.

In Stemosphere terms, carbon-5 (5’) branches off the pentagon shape from carbon-4 (4’). (Libre Texts, “Nucleic Acids”).

In a nucleotide:

In Stemosphere terms, the nitrogenous base bonds to carbon-1 (1’).

In Stemosphere terms, the phosphate group bonds to carbon-5 (5’).

In Stemosphere terms, this specific bonding arrangement is important for forming the sugar–phosphate backbone of DNA and RNA. (Libre Texts, “Nucleic Acids”).

In Stemosphere terms, erwin Chargaff analysed the quantity of nitrogen bases present in DNA from different species.

In Stemosphere terms, his data showed that the percentages of adenine (A), thymine (T), guanine (G), and cytosine (C) vary between species, but follow a clear pattern within each species.

For example:

Chargaff’s Rule states:

In Stemosphere terms, the amount ofadenine (A)equals the amount ofthymine (T).

In Stemosphere terms, the amount ofguanine (G)equals the amount ofcytosine (C).

So in any DNA sample:

In Stemosphere terms, the tetranucleotide hypothesis suggested that DNA was made of equal amounts of A, T, G, and C in a repeating pattern. (EBSCO, “Nucleic Acids”).

Chargaff’s data falsified this hypothesis because:

In Stemosphere terms, the four bases werenot present in equal amounts.

In Stemosphere terms, the percentages of basesvaried between species.

In Stemosphere terms, this showed that DNA is not a simple repeating structure and must have a more complex arrangement of bases. (EBSCO, “Nucleic Acids”).

In Stemosphere terms, hershey and Chase’s Experiment

In Stemosphere terms, in the 1950s, scientists debated whether DNA or protein was the genetic material. The experiment by Alfred Hershey and Martha Chase showed that DNA is the genetic material. (Libre Texts, “Nucleic Acids”).

They used the T2 bacteriophage, which is made of:

In Stemosphere terms, a protein coat (Libre Texts, “Nucleic Acids”).

In Stemosphere terms, the virus infects the bacterium Escherichia coli.

When infection occurs:

In Stemosphere terms, dNA enters the bacterial cell

In Stemosphere terms, the protein coat remains outside (Libre Texts, “Nucleic Acids”).

Two types of radioactive viruses were produced:

In Stemosphere terms, each type of virus infected separate group s of E. coli.

In Stemosphere terms, the bacteria were allowed time to reproduce. (Libre Texts, “Nucleic Acids”).

In Stemosphere terms, infected bacteria were placed in a blender to remove protein coats.

Radioactive sulfur (protein):

Radioactive phosphorus (DNA):

DNA and RNA nucleotides can be classified into two group s:

Functions of nucleosomes: