Nucleic acids

Question 1

What does the genetic material in the cell (DNA) do?

Answer 1

The genetic material in the cell is DNA. DNA “controls” the cell by providing the information
on how to make proteins. It is essentially an instruction book for every cell in the body. The
proteins made then regulate cell metabolism and behaviour (e.g. enzyme controlled chemical
reactions).

Question 2

What is a nucleotide?

Answer 2

A nucleotide is the monomer of a nucleic acid. It is made up from 3 components.

Question 3

What are the three components which make up a nucleotide?

Answer 3

1. Phosphate group
2. Organic base - a nitrogenous base
3. Pentose sugar

Question 4

what are the three types of RNA?

Answer 4

There are 3 types of RNA:
a) Messenger RNA (mRNA)
b) Transfer RNA (tRNA)
c) Ribosomal RNA (rRNA) – consist of a large and a small subunit, along with proteins
creates a ribosome.

Question 5

What is the pentose sugar in a DNA nucleotide?

Answer 5

In a DNA nucleotide the pentose sugar is a deoxyribose sugar. DNA also contains one of 4
organic bases: adenine, cytosine, guanine or thymine.

Question 6

What is the pentose sugar in a RNA nucleotide?

Answer 6

In a RNA nucleotide the pentose sugar is a ribose sugar. RNA also contains one of 4 organic
bases: adenine, cytosine, guanine or uracil.

Question 7

How are nucleic acids formed?

Answer 7

Nucleic acids are formed when many thousands of nucleotides link to form a long
chain.
• The link between adjacent nucleotides is from the phosphate group of one nucleotide
to the sugar molecule in the next nucleotide (sugar-phosphate link
• This is a covalent bond and makes the “backbone” of the nucleic acid stable and
strong
• The nitrogenous bases are not involved in these linkages and stick out from the
backbone.

Question 8

What is the basis of the genetic code and how information is stored in DNA?

Answer 8

The sequence of the bases along the nucleotide chain is variable. This is the basis of
the genetic code and how information is stored in DNA.

Question 9

What are the four organic bases in DNA?

Answer 9

The 4 organic bases in DNA:
Adenine - A
Thymine - T
Cytosine - C
Guanine - G

Question 10

What is the structure of DNA?

Answer 10

DNA consists of two parallel nucleotide strands
held together by hydrogen bonding between the
organic bases (base pairing).

Question 11

What do the two strands fold into a helix shape to create?

Answer 11

a double helix.

Question 12

What must happen in order for the two strands of DNA to remain parallel?

Answer 12

To make sure the two strands remain parallel a two
ring base (purine) must always bond with a one ring
base (pyrimidine).

Question 13

What are the complimentary base pairs?

Answer 13

Adenine bonds with Thymine (A-T)

- Cytosine bonds with Guanine (C-G)

Question 14

what is a triplet code?

Answer 14

Every three bases in the DNA molecule are known as a triplet and codes for an amino acid, so
the ‘sequence of bases’ in a large strand of DNA will contain the information for the
‘sequence of amino acids’.

Question 15

What is a gene and what is its role?

Answer 15

The DNA molecule is organised into sections called genes. Each gene contains the code for a protein which controls the activities of a cell and in turn our
characteristics.

Question 16

How does a change in the base sequence of DNA

could lead to an enzyme not functioning or a non-functional protein.

Answer 16

DNA base sequence codes for sequence of amino acids/primary structure

• Changing the hydrogen, ionic and disulphide bonds between R groups
• Leading to a change in tertiary structure/shape of active site
• Substrate unable to bind/ no enzyme-substrate complexes formed

Question 17

What is an allele and give an example?

Answer 17

An allele is a different form of the same gene For example, the gene that controls
hair colour has many different alleles: red, blonde, brown, and black

Question 18

what do the differences in genes cause?

Answer 18

These differences in genes are extremely important in variation, and help cause the differences between members of the same species and between parents and offspring.

Question 19

where is non-coding DNA?

Answer 19

There is non- coding DNA both in the gene and between genes.

Question 20

What lies between the genes and what do they contain?

Answer 20

Between the genes are mini-satellite regions. Each region contains a core sequence of bases
which is repeated a number of times

Question 21

what lies within the gene?

Answer 21

There is also non-coding DNA within the gene. The gene is made up of a number of regions of
coding DNA and between these are introns (non-coding DNA)

Question 22

What is semi-conservative replication?

Answer 22

When any new cells are created in the body, the DNA must be copied (replicated) at
cell division, so that each of the daughter cells receives a copy of the DNA.
Each new DNA molecule contains one strand of the original DNA molecule and one new
strand

Question 23

describe the process of semi-conservative replication?

Answer 23

An enzyme called DNA Helicase attaches to the DNA and moves along the molecule,
unwinding the DNA and breaking the hydrogen bonds between the complementary
bases.
2. The two strands start to separate.
3. Free DNA nucleotides now base pair with the exposed bases on the two separating
DNA strands (normal rules of base pairing apply).
4. The enzyme DNA polymerase now joins adjacent nucleotides together by forming the
phosphodiester bonds. The sugar-phosphate backbone is produced.
5. This occurs on both original strands, so that two copies are made. Each contains an
original and a new strand and is identical to the original DNA.