3.1) DNA - the code of life

Question 1

What are the 2 nucleic acids found in cells?

Answer 1

1) Deoxyribonucleic acid (DNA)

2) Ribonucleic acid (RNA)

Question 2

Who discovered DNA and who did not receive the Nobel Peace Prize?

Answer 2

Maurice Wilkins
Francis Crick
James Watson
Rosalind Franklin (didn’t get Nobel Peace Prize)

Question 3

Where is DNA found?

Answer 3

Mainly in the nucleus of a cell

Forms part of the chromosomes that make up the chromatin network

Question 4

Define chromatin

Answer 4

Chromosomal material made up of DNA, RNA and histone proteins as found in a non-dividing cell

Question 5

What is extranuclear DNA?

Answer 5

Small amounts of DNA are found outside the nucleus in mitochondria in plants/animals and chloroplasts in plants

Question 6

What is the shape of the DNA

Answer 6

Long, twisted ladder

3D double helix

Question 7

How is a nucleotide made up

Answer 7

sugar (deoxyribose)
phosphate molecule
nitrogenous base

Question 8

What are the 4 nitrogenous bases

Answer 8

adenine
thymine
guanine
cytosine

Question 9

How is the double helix made up

Answer 9

• Outer two strands formed by chain of alternating sugar/phosphate links - strong
• rungs of ladder - pairs of bases linked by weak hydrogen bonds
• base pairs attached to sugar molecules

Question 10

Which base pairs link together

Answer 10

A - T (or U)

G - C

Question 11

How are base pairs classified ?

Answer 11

Purines & Pyrimidines

Question 12

Define purines and examples

Answer 12

Purines - 2 fused rings of nitrogen, carbon and hydrogen atoms
Eg. Guanine and adenine

Question 13

Define pyrimidines and examples

Answer 13

Pyrimidines - 1 ring of similar atoms - SMALLER than purines
Eg. Thymine, cytosine and uracil

Question 14

What determines the genetic code?

Answer 14

Sequence of nucleotides

Question 15

What is the role of DNA?

Answer 15

1) carry hereditary info in the form genes
2) coding for protein synthesis
3) can replicate

Question 16

What is non-coding ?

Answer 16

1) less than 2% codes, rest is non-coding
2) protein-coding of DNA called exons and are interrupted by non-coding regions called introns
3) complex organisms have more non-coding
4) non-coding regions form functional RNA molecules

Question 17

Define replication

Answer 17

Process defined as the process of making a new molecule DNA from an existing DNA molecule that is identical to the original molecule.

Question 18

Why is replication necessary?

Answer 18

Genetic code is passed on to each new daughter cell formed during cell division

Question 19

Explain replication process

Answer 19

1) process is catalysed by the enzyme polymerase
2) double helix unwinds
3) weak hydrogen bonds holding the base pairs together break, allowing the two strands to part
4) each of the single bases are exposed
5) free nucleotides in the nucleoplasm become attached to their matching, exposed base partners

1 double helix becomes 2 double helices; 2 daughter DNA molecules each to form a double helix & winds itself around the histones which forms a chromosome.