AS RECAL DNA relication & Protein Synthesis

Question 1

Explain how the structure of DNA is related to its functions

Answer 1

1. sugar phosphate backbone double stranded; provides stability/ strength
2. Long/large; stores lots of info
3. Helix/ coiled; compact
4. Base sequence, allows info to be stored
5. Double stranded; both existing strands can act as templates; replicates semi- conservatively
6. Weak H Bonds; strands easily separated

Question 2

Describe and explain how the structure of DNA results in accurate replication

Answer 2

1. 2 strands; semi-conservative replication
2. Base pairing held together by H bonds
3. Weak H bonds; strands easily separated
4. Bases exposed and act as a template
5. A-T, C-G
6. DNA made has 1 parent strand, 1 new strand

Question 3

Messenger RNA is used during translation to form polypeptides. Describe how mRNA is produced in the nucleus of a cell

Answer 3

1. DNA helicase
2. Breaks H bonds b/t base pairs, exposing them
3. Only 1 strand acts as a template
4. RNA nucleotides attracted to exposed based
5. A-U, C-G
6. RNA polymerase joins the RNA nucleotides together, to form pre-mRNA
7. Pre-mRNA is spliced; introns removed to form mRNA

Question 4

Starting with mRNA in the nucleus, describe how a molecule of protein is synthesised

Answer 4

1. mRNA leaves the nucleus through nuclear pore
2. Enters the ribosome
3. tRNA molecules bring amino acids to the ribosome
4. A specific tRNA molecule exists for a specific amino acid
5. Anticodon of tRNA complementary to codon on mRNA
6. Peptide bonds form b/t adjacent amino acids
7. tRNA detaches and leaves to collect another amino acid
8. Ribosome moves along mRNA

Question 5

Explain how a mutation can result in the production of a non- functional protein receptor

Answer 5

1. Change in DNA base sequence
2. Change in amino acid sequence
3. This alters position of hydrogen/ ionic/ disulfide bonds
4. And causes a change in the tertiary structure of the receptor