Molecular genetics

Question 1

DNA

Answer 1

DNA is a molecule that carries genetic information and is important for cellular function such as cell division

Question 2

DNA structure (1)

Answer 2

1. A small sequence of DNA carries a gene that is used to code for polypeptides
2. Each DNA molecule consists of 2 antiparallel polynucleotide chains that twist around each other to form a double helix
3. A DNA molecule is wrapped around a histone protein to form a chromatin thread
4. The chromatin thread condenses and coils to form chromosomes

Question 3

DNA structure (2)

Answer 3

• The basic unit of DNA is a nucleotide
• Nucleotides are made up of:
  1. A phosphate group
  2. A sugar
  3. A Nitrogenous base

Question 4

The 4 types of nitrogenous base

Answer 4

1. Adenine
2. Thymine
3. Guanine
4. Cytosine

Question 5

Pairing of bases

Answer 5

• Adenine is paired to thymine (AT)
• Guanine is paired to cytosine (GC)

Question 6

Genes

Answer 6

A specific sequence of DNA that codes for a polypeptide

Question 7

Synthesis of proteins

Answer 7

• The order of bases in a gene is called the genetic code
• A genetic code codes for a specific polypeptide
• For synthesis of proteins, two processes occur:
  1. Transcription
  2. Translation

Question 8

Transcription

Answer 8

• The transfer of information from DNA to mRNA
• Occurs in the nucleus
• The template strand of DNA is copied into a mRNA molecule which leaves the nucleus

Question 9

Difference of DNA and RNA

Answer 9

1. DNA consists of deoxyribonucleic acid while RNA consists of ribonucleic acid
2. DNA consists of adenine, thymine, guanine and cytosine while RNA consists of adenine, uracil, guanine and cytosine
3. DNA is double stranded and permanently stored in the nuclues while RNA is single stranded and temporary made when needed

Question 10

Translation

Answer 10

• The conversion of mRNA to a sequence of amino acids
• Occurs in the cytoplasm
• Every 3 bases (codon) codes for 1 amino acid

Question 11

Genetic engineering

Answer 11

• It is a technique used to transfer genes from one organism to another
• Whereby, genes are cut from the cells of one organism and inserted into the cells of another organism, allowing it to express the transferred genes

Question 12

Transgenic organism

Answer 12

An organism that contains a foreign gene from another organism of the same or different species

Question 13

Production of insulin

Answer 13

Importance:
- Diabetes type 1 patients are unable to control their blood glucose level, so insulin is used to treat them
- Human insulin gene is taken from human cells and transferred into E.coli bacteria
- E.coli bacteria can then mass produce insulin

Question 14

Process of production of insulin

Answer 14

1. Cut the human insulin gene from a chromosome using a restriction enzyme to produce sticky ends
2. Obtain a bacterial plasmid and cut it using the same restriction enzyme to produce sticky ends complementary to the human insulin gene
3. Insert the human insulin gene into plasmid using DNA ligase to form a recombinant plasmid
4. Mix the recombinant plasmid with E.coli bacteria by applying heat to open transient pores in the cell membrane for plasmid to enter
5. Insulin produced by the transgenic bacteria is extracted and purified

Question 15

Benefits of genetic engineering

Answer 15

1. Low-cost to produce medicine
   - allows drugs to become more accessible and more patients to be treated
2. Develop crops that kill pests or are resistant to pesticides
   - Reduces the use of pesticides and reducing damage to environment

Question 16

Ethical concerns of genetic engineering

Answer 16

1. New proteins in genetically modified food may cause allergies and affect human health
2. Consider welfare of animals when using animals in medical research to study diseases