2.1 Structure of RNA and DNA

Question 1

What are the three components of nucleotides

Answer 1

1. Pentose sugar
2. A phosphate group
3. A nitrogen containing base. e.g. Cytosine, Thymine, Guanine and adenine. In RNA, Uracil instead of thymine

Question 2

How are the pentose sugar, phosphate group and organic base joined together

Answer 2

As a result of condensation reactions, to form a mononucleotide

Question 3

How can two mononucleotides be joined together

Answer 3

As a result of a condensation reaction between the deoxyribose sugar of one mononucleotide and the phosphate group of another.

Question 4

What is the bond between mononucleotides called and what is the name of the resultant product

Answer 4

A phosphodiester bond, forming a dinucleotide

Question 5

Desribe the strucutre of RNA

Answer 5

Single, short, polynucleotide chain in which the pentose sugar is always RIBOSE and the organic bases are adenine, uracil, cytosine and guanine

Question 6

What are ribosomes made up of

Answer 6

Ribosomal RNA and proteins

Question 7

Describe the structure of DNA

Answer 7

Double, long, polynucleotide chain in which the pentose sugar is always DEOXYRIBOSE and the organic bases are adenine, thymine, cytosine and guanine. The two chains are joined together by hydrogen bonds

Question 8

Why is DNA a stable molecule

Answer 8

1. The phosphodiester backbone protects the more chemically reactive bases inside the double helix
2. Hydrogen bonds link the organic bases. Cytosine and guanine have 3 hydrogen bonds between them, therefore the higher number of C-G pairings the more stable the molecule

Question 9

What is the function of DNA

Answer 9

To be the hereditary material responsible for passing genetic information from cell to cell.

Question 10

How is DNA’s structure adapted to carry out its functions

Answer 10

1. It is a very stable structure which normally passes from generation to generation unchanged, except for mutation
2. Its two separate strands are joined only with hydrogen bonds which allow them to separate during DNA replication
3. It is a large and long molecule meaning it is capable of carrying large amounts of genetic information
4. By having base pairs within the helix, the genetic information is protected from being corrupted by outside forces
5. Base pairing leads to DNA being able to replicate and to transfer information as mRNA