Gene expression

Question 1

What does Gene expression involve?

Answer 1

the
transcription and translation of DNA
sequences.

Question 2

Name the 3 Types of RNA

Answer 2

1. mRNA
2. tRNA
3. rRNA

Question 3

Describe RNA

Answer 3

RNA is single stranded
Composed of:
nucleotides containing ribose sugar,
phosphate.
and Bases :
cytosine, guanine, adenine and uracil.

Question 4

Describe mRNA

Answer 4

transcribed from DNA in the
nucleus and translated into proteins by
ribosomes in the cytoplasm.

Question 5

What is each triplet of bases on the mRNA molecule called?

Answer 5

A codon which codes for a specific amino acid.

Question 6

Describe 2 tRNA Things

Answer 6

folds due to complementary base pairing. Each tRNA molecule carries its specific amino acid to the ribosome.

A tRNA molecule has an anticodon at one end and an
attachment site for a specific amino acid at
the other end.

Question 7

Describe rRNA

Answer 7

Ribosomal RNA (rRNA) and proteins form
the ribosome.

Question 8

Describe Transcription

Answer 8

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. RNA splicing occurs by removing the introns of the primary transcript and the exons are joined together to form the mature transcript.

Question 9

What are the coding regions

Answer 9

Exons

Question 10

What are the non coding regions

Answer 10

Introns

Question 11

Describe 6 stages of Translation

Answer 11

1. Translation begins at a start codon and ends
   at a stop codon.
2. The ribosome exposes one codon on the mRNA allowing tRNA to bring a specific amino acid to the ribosome.
3. The correct anticodon on the tRNA will complementary base pair with the codon on the mRNA, bringing the correct specific amino acid with it.
4. The ribosome exposes the next codon where another tRNA and its amino acid will complementary base pair with that codon.
5. Peptide bonds join the amino acids
   together.
6. Each tRNA then leaves the
   ribosome as the polypeptide is formed.

Question 12

What happens as a result of alternitive RNA splicing

Answer 12

Different proteins can be expressed from
one gene

Question 13

What happens depending on which exon is retained

Answer 13

Different mature mRNA transcripts
are produced from the same primary
Transcript.

Question 14

How is the Phenotype determined

Answer 14

1. by proteins
   produced as the result of gene expression.
2. Environmental factors