3. Nucleic acid primary

Question 1

Nucleic acids:

Answer 1

Nucleic acids store, transmit, and help express hereditary information.
2 types of nucleic acids :
o Deoxyribonucleic acid (DNA)
o Ribonucleic acid (RNA)

Question 2

Central dogma in the molecular biology - exceptions to the original scheme.

Answer 2

The genetic information flows from DNA through RNA, to protein, i.e.
“DNA makes RNA makes protein”
Fig 2

Exceptions to the original scheme.
- Independent gene expression in the mitochondria and chloroplasts.
-Many RNA Molecules not translated into protein, but function as RNAs on their own. Their genes are known as RNA genes.
-Retroviruses (e.g. HIV) use **reverse transcription **to synthesize DNA copy over RNA molecule.
-influenza and hepatitis C viruses copy RNA genome directly into RNA without use of DNA- RNA replication.

Question 3

Primary structure of DNA - formation of the nucleotide and polynucleotide chain. Watson and Crick’s model

Answer 3

-DNA is a two-chain structure.
-two chains run antiparallel (in opposite 5’-3’ directions)
-chains are linked to complimentary nitrogenous bases:
* Adenine-Thymine (two hydrogen bonds)

• Guanine-Cytosine (three hydrogen bonds)

-When heated the H bonds break and the chains separate (denaturation)
-When returning to a normal temp they pair again (renaturation).