AS Level Biology Exam Question about DNA?

The Question is:

i) The sequence of bases on one strand of DNA is important for protein synthesis. What is its role?

ii) Give one advantage of DNA molecules having two strands.


3 Answers

  • 1 decade ago
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    As you were told you have the Sense strand which is the coding strand and the AntiSense which is the non-coding strand

    the sequence of bases (A,T,C,G) determines the sequence of the protein to be built

    Every three consecutive bases(AAG for example) are called a codon, each codon codes for a specific amino-acid molecule to be added to the growing protein, so a sequence on the Sense strand that goes like this : AAGCGCATCGATCCTAGG will be read by the RNA polymerase like this AAG CGC ATC GAT CCT AGG

    and the amino acid sequence of the protein would be :

    Lysine-Arginine-IsoLeucine-Aspartatic Acid-.....

    but in the RNA strand instead of T you'll gave U

    2) in addition to the stability of the molecule that prevents degradation and rapid changes(double stranded helical molecules are more stable than one stranded molecules), an additional advantage is that by having to strands which are complementary, you'll have a "backup" of the DNA data, so if a mutation occurs, you can use the backup strand to repair the other strand by the repair mechanism found in cells

    hope this helps

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  • 1 decade ago

    As we know. there are two strands of DNA, the sense strand, and the Anti sense strand. The Bases on messenger RNA are according to the Sense strand only. The difference is that the messenger RNA does not contain thymine and contains Uracil instead.

    There are Hydrogen Bonds between the Nitrogen bases on opposing strands which gives the molecule stability. When DNA replicates, semi conservative replication, the new strands are made from both the strands.

    Hope this helps.

    Source(s): Endorsed By UCIE :AS and A Level Biology by Mary Jones, Richard Fosbery, Dennis Taylor and Jennifer Gregory.
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  • 4 years ago

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