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VICBiologyQuick questions
Unit 3: How do cells maintain life?
Quick questions on Nucleic acid structure (DNA and RNA): VCE Biology Unit 3
10short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the nucleotide?Show answer
Every nucleotide has three components:
What are bases?Show answer
The four DNA bases are the purines adenine (A) and guanine (G), and the pyrimidines thymine (T) and cytosine (C).
What is complementary base pairing?Show answer
A pairs with T through two hydrogen bonds; G pairs with C through three hydrogen bonds. Because pairing is specific, each strand carries the complementary sequence of the other, which allows accurate replication.
What is stability and access?Show answer
The sugar-phosphate backbone is on the outside; bases face inward. Hydrogen bonds between bases are individually weak but collectively stable, while still allowing the strands to separate when enzymes such as helicase unzip the helix.
What is messenger RNA?Show answer
A linear single strand that carries the genetic message from DNA to the ribosome. It is read in codons (triplets of bases). In eukaryotes, mature mRNA has a 5' cap, a 3' poly-A tail, and introns removed by splicing.
What is transfer RNA?Show answer
A short folded RNA (about 76 to 90 nucleotides) shaped like an inverted L (cloverleaf in two dimensions). It carries a specific amino acid on its 3' end and presents a three-base anticodon that pairs with a codon on mRNA. There is at least one tRNA for each of the 20 amino acids.
What is ribosomal RNA?Show answer
Combines with proteins to form the two subunits of the ribosome. rRNA does the catalytic work of forming peptide bonds, so the ribosome is described as a ribozyme.
What is q1?Show answer
State the three components of a nucleotide and identify which two differ between DNA and RNA. [3 marks]
What is q2?Show answer
A single strand of DNA reads 5'-ATGCGGTAC-3'. (a) Write the complementary DNA strand with correct polarity. (b) Write the mRNA sequence transcribed from the original strand acting as template.
What is q3?Show answer
Refer to the three forms of RNA. (a) State the function of mRNA, tRNA and rRNA. (b) Explain why an mRNA vaccine cannot alter host DNA.