1) What type of biological molecule (macromolecule) is DNA?

2. This polymer is formed by the connection of many millions of monomer units. What is the monomer unit of DNA?

3. Consider this monomer. What three structural components make up this DNA monomer?

4. Name the four nitrogenous bases that makeup DNA. .

5. Erwin Chargaff is one of many researchers that made important contributions to understanding the structure of DNA. His discovery, announced in 1949, was called “Chargaff’s Rule”. What is Chargaff’s rule?

6. How are Hydrogen bonds involved in the structure of DNA? Explain.

7. What information did Rosalind Franklin’s X-ray crystallography images provide about the structure of DNA?

8. If a species has 35% adenine in its DNA, what is the percentage of the other three nitrogenous bases? Hint: look at page 345 (analyzing data) for an example of this type of question.

9. Define the following terms:

Base Pair:

Antiparallel:

Chromosome (might need to look up in the Glossary):

1.      DNA comes under the category of nucleic acids.  

2.      The monomer unit of DNA is nucleotides.

3.      Each nucleotide monomer in DNA is made up of a nitrogenous base, deoxyribose, and a phosphate group.

4.      The nitrogenous bases found in DNA are adenine, guanine, cytosine, and thymine.

5.      Chargaff's rule is also known as the equivalence rule. It states that the concentration of adenine and thymine will always remain the same, the concentration of cytosine and guanine will always remain the same in the DNA of any species.

6.      DNA is a double helix structure; the hydrogen bonds make it possible. Hydrogen bonds bind the complementary bases. Hydrogen bonds also link the strands of DNA together.

7.      From Rosalind Franklin's structure of DNA, it was confirmed the DNA exists in a helical conformation.

8.      If the adenine is 35 %, the thymine will be 35%, cytosine is 15% and guanine is also 15%.

9.      

·        Base pairs are fundamental and structural units of a double-stranded DNA molecule. Adenine forms a base pair with thymine by 2 hydrogen bonds. Cytosine makes base pair with guanine by 3 hydrogen bonds.

·       Antiparallel-  When two biopolymers run parallel to each other but in opposite direction, are called antiparallel. The DNA is a double-stranded molecule, it means the head of one strand is always be against the tail of another strand. In the DNA, the direction of strands is termed polarity.

·        Chromosomes- these are a thread-like structure that is found in the nucleus of every cell. Chromosomes pass the genetic information from one generation to another.

Step-by-step explanation

1.      DNA or deoxyribonucleic acid is a nucleic acid that stores genetic information.

2.      It is a polymer of nucleotides in DNA, the nucleotides remain attached by covalent bonds.

3.      The sugar present in DNA is a 5-carbon sugar.

4.      Adenine and guanine are purine nitrogenous bases, while cytosine and thymine are pyrimidine nitrogenous bases. In RNA, uracil is present instead of thymine.

5.      Chargaff's rule is very important to understand the structure of DNA. The fact is adenine always makes bonds with thymine, so their quantity will always same, so is true for cytosine and guanine.

6.      The nitrogenous bases in DNA form hydrogen bonds with other nitrogenous bases. The adenine makes 2 hydrogen bonds with thymine while, cytosine makes three hydrogen bonds with guanine.

7.      The helical conformation of DNA was later confirmed by Francis crick and James Watson.

8.      The total nitrogenous bases are 100 %.

If the adenine is 35%, according to Chargaff's rule, the thymine is also 35%.

Then 30% is left,

The cytosine and guanine present in equal quantity, so,

The cytosine is 15% and guanine is also 15%.