KA3- Gene Expression&Protein Synthesis

Question 1

What is gene expression?

Answer 1

Gene expression involves the transcription and translation of DNA sequences to form a protein.

Question 2

What are nucleotides made up of in a RNA molecule?

Answer 2

A phosphate molecule, a base and a ribose sugar.

Question 3

What is the function of mRNA?

Answer 3

To carry a complementary copy of the DNA code from the nucleus to the ribosome (transcription).

Question 4

What is the function of tRNA?

Answer 4

To carry specific amino acids to ribosomes where they can be assembled to form a protein (translation).

Question 5

What are the RNA base pairs?

Answer 5

Adenine- Uresil
Cytosin- Gyonine

Question 6

How are proteins formed?

Answer 6

They formed by joining amino acids together in a specific sequence.

Question 7

What determines the order of amino acids?

Answer 7

The order of the bases on the DNA.

Question 8

What is transcription?

Answer 8

Transcription occurs in the nucleus and produces a strand of mRNA complementary to a region of DNA called a gene.

Question 9

Describe the process of Transcription.

Answer 9

1. RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between the bases.
2. RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides by complementary base pairing.
3. Primary mRNA transcript only codes for 1 protein so only one gene is transcribed to form mRNA.

Question 10

What is mRNA splicing?

Answer 10

mRNA splicing occurs after transcription but before translation. It occurs because not all nucleotides in a gene code for an amino acid.

Question 11

What happens during mRNA splicing?

Answer 11

The primary transcript contains regions called exons and introns. Exons are the coding regions while introns are the non coding regions. Introns are removed from the strand and exons are spliced together to form a mature mRNA transcript. The order of exons is unchanged during splicing.

Question 12

What is a codon?

Answer 12

A triplet of bases on the mRNA molecule and codes for a specific amino acid.

Question 13

What is translation?

Answer 13

The translation of mRNA into a protein at a ribosome.

Question 14

What is an anticodon?

Answer 14

Triplet of bases which are complementary to a codon.

Question 15

Describe the process of translation.

Answer 15

1. A mature mRNA ,molecule binds onto a ribosome.
2. Anticodons on tRNA bond to codons on mRNA by complementary base pairing, translating the genetic code into a sequence of amino acids.
3. Pepetide bonds join the amino acids together.
4. Each tRNA leaves the ribososme as the polypepetide chain is formed and it is free to collect another amino acid.

Question 16

What is alternative RNA splicing?

Answer 16

When one gene can create many proteins as a result of alternative RNA splicing.