MOLECULAR GENETICS

Question 1

What is DNA?

Answer 1

Molecule that carries genetic information used in the development and functioning of all organisms

Question 2

What is each DNA molecule made up of?

Answer 2

It is made up of basic units called nucleotides, each consisting of:
1. A deoxyribose sugar (5-carbon sugar)
2. A phosphate group
3. A nitrogenous base

The phosphate and deoxyribose are joined together to form the backbone of the DNA molecule, while the nitrogenous base attaches to the sugar.

Question 3

What are the types of nitrogenous bases?

Answer 3

1. Adenine (A)
2. Guanine (G)
3. Cytosine (C)
4. Thymine (T)

Question 4

How is the sugar-phosphate backbone formed?

Answer 4

Nucleotides in a polynucleotide strand are linked together by phosphodiester bonds, which form the backbone. This is formed between the phosphate group of one nucleotide and the hydroxyl group of another nucleotide.

Question 5

How is the double helix structure of DNA formed?

Answer 5

When two strands of polynucleotides wrap around each other. They are held together when the nitrogenous bases on one strand form hydrogen bonds with the nitrogenous bases on the other strand.

Question 6

Define complementary base pairing

Answer 6

When each type of base on one strand forms hydrogen bonds with only one type of base on the other strand

Adenine - Thymine (Apples in the Tree)
Cytosine - Guanine (Car in the Garage)

Question 7

Define genetic engineering

Answer 7

Technique where genes of interest are transferred and inserted into the genome of a specific organism

Question 8

Define transgenic organisms

Answer 8

Organisms that possess a gene/genes that have been transferred from another species (GMO)

Question 9

Define vector

Answer 9

Carrier DNA molecule into which the desired gene can be inserted to genetically engineer an organism

e.g. a plasmid

Question 10

Define gene

Answer 10

Single unit of hereditary information consisting of a specific nucleotide sequence located on the chromosome for the production of a single polypeptide

Question 11

What is the procedure for producing human insulin?

Answer 11

1. Isolate the desirable human insulin gene by cutting it from the DNA using a restriction enzyme
2. Prepare bacterial plasmids by cutting a bacterial cell open with the same restriction enzyme. Sticky ends of the gene fragment and the plasmid are complementary
3. Mix the plasmids with the insulin gene fragments. The cut ends join together with the help of the ligase enzyme
4. Recombinant plasmids are mixed with E. coli bacteria
5. Heat shock is applied to open up the pores of the bacterial cell membranes, allowing the plasmids to enter the bacterial cells
6. Place bacteria in fermenters. Bacteria makes copies of the plasmid when they reproduce by mitosis
7. At the end of fermentation, bacteria cells are lysed
8. Insulin is extracted and purified by crystallisation