STPM Biology - chapter 3: Revision essay question 1

1. Elaborate on the importance of the DNA structure in relation to

i. gene replication
ii. protein synthesis                                                                 [11]

Answer:


(i) ** Any 5

1. DNA contains genetic code for semi-conservative replication

2. The double helix structure of DNA is separated when the hydrogen bonds between bases break 

3. free nucleotides found in nucleoplasm are now able to pair complementary with the exposed nucleotides on DNA.

4. the number of bases is fixed by the length of the DNA molecule

5. Pairing must be exact base pairing: A=T, C≡G

6. The content of the DNA does not change

7. the information in the genetic code is passed down to the daughter cells

(ii) ** Any 6 (pls revise process of transcription and translation)


1. The DNA double helix opens/separates at a specific point to expose its sequence of specific genes
2. the weak hydrogen bonds enable the DNA double helix to open easily and this is catalysed by DNA polymerase.
3. Free nucleotides then arrange accurately in a complementary manner on the template.
4. Complementary bases precisely pair with each other: A=U, C≡G to ensure accurate transcription

5. On the mRNA, 3 bases form a codon
6. Each specific codon is a code for a specific amino acid
7. After transcription, mRNA separate from the template and move through the nuclear pore to the cytoplasm to perform translation  on the ribosome.
8. four different bases on the DNA are sufficient to supply all the codons for all the different types of amino acids needed