DNA and protein synthesis

Question 1

What is a gene?

Answer 1

A gene is a length of DNA that acts as a coding device for the synthesis of a particular polypeptide

Question 2

What does the genetic code involve?

Answer 2

Three consecutive bases each coding for a particular amino acid.

Question 3

What are key features of the genetic code?

Answer 3

1. Non overlapping
2. Degenerate - Amino acids have more than one possible code
3. You have stop and start base triplets
4. It is universal

Question 4

Where is the genetic code kept?

Answer 4

In the chromosomes in the nucleus

Question 5

Why is the code transcribed by mRNA

Answer 5

1. DNA is too long to exit the cell
2. The cytoplasm would put it at risk of damage
3. Many polypeptides can be synthesised simultaneously as it can be copied at numerous points

Question 6

Give some features of DNA and mRNA

Answer 6

DNA

1. Longer than mRNA
2. Double stranded
3. Deoxyribose sugar
4. ATGC
5. Located in the nucleus

mRNA

1. Shorter than DNA
2. Single stranded
3. Ribose sugar
4. AUGC
5. Produced in the nucleus but found throughout the cell

Question 7

What is a gene mutation?

Answer 7

A spontaneous change in the DNA of a molecule

Question 8

What are two examples of a gene mutation

Answer 8

Substitution

Base deletion

Question 9

Substitution

Answer 9

A base gets changed for a different base, due the degenerate nature of the genetic code this may not cause for a big change

Question 10

Base deletion describe

Answer 10

A base is deleted from the template strand, this causes all subsequent bases to change and will cause a huge change in the polypeptide produced

Question 11

How does a mutation lead to a change in the protein produced?

Answer 11

The change in the base sequence leads to the change in mRNA which leads to a change in the amino acid produced and the sequence of polypeptide which leads to a different globular conformation of the protein