DNA structure and function

Question 1

What are nucleic acids?

Answer 1

They are the genetic material of all living things and viruses. There are 2 types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

Question 2

Is a nucleotide a monomer or polymer? What are the 3 components that make up nucleotides?

Answer 2

A nucleotide is a monomer. It consists of:

• a nitrogenous base
• pentose sugar
• phosphate

Question 3

What are the 2 parent compounds the nitrogenous bases are derived from?

Answer 3

• Purine bases: A (adenine) and G (guanine)

- Pyrimidine bases: C (cytosine) and T (thymine) / U (uracil - for RNA)

Question 4

Nucleotides are formed through _______ reactions, with the formation of 2 ____ molecules.

Answer 4

Nucleotides are formed through condensation reactions, with the formation of 2 water molecules.

Question 5

What is a phosphodiester bond? It is formed by what reaction?

Answer 5

A phosphodiester bond is a covalent bond between the 5’-phosphate group of one nucleotide and the 3’ OH group of another nucleotide. It is formed by a condensation reaction and a water molecule is lost in the process.

Question 6

Nucleotides combine together to form huge molecules called ____ ___ (or polynucleotides). It occurs through _____ reaction between the _____ group of one nucleotide and the ____ group of another nucleotide.

Answer 6

Nucleotides combine together to form huge molecules called nucleic acids (or polynucleotides). It occurs through condensation reaction between the phosphate group of one nucleotide and the sugar group of another nucleotide.

Question 7

What are the 2 traits that help achieve DNA stability?

Answer 7

1. Alternating sugar and phosphate molecules form a sugar phosphate backbone with one of the bases attached to each of the sugar molecules along the strand.
2. Two hydrogen bonds are formed between A and T, three hydrogen bonds are formed between C and G. This is known as complimentary base pairing.

Question 8

DNA strands are arranged _____. One chain runs from _’ to _’ whilst the other runs from _’ to _’.

Answer 8

DNA strands are arranged antiparallel. One chain runs from 5’ to 3’ whilst the other runs from 3’ to 5’.

Question 9

RNA is relatively ____ in length and is single stranded. It contains ___ (_) instead of thymine (T).

Answer 9

RNA is relatively short in length and is single stranded. It contains uracil (U) instead of thymine (T).

Question 10

The role of DNA is to instruct cells to make specific polypeptides and proteins. How is genetic material organised?

Answer 10

DNA molecule is packaged into chromosomes, each chromosome is made out of DNA coiled 1.75 times around a core of histone proteins.
A sequence of nucleotides makes up a gene and the sequence can vary. Each gene controls the formation of a single polypeptide.