IB Docs (2) Team MC test: Nucleic acids
Multiple choice test on B.8 Nucleic acids
Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.
If you get an answer wrong, read through the explanation carefully to learn from your mistakes.
Which carbon atom on the pentose sugar does the phosphate group bond to when nucleotides condense together to form phosphodiester bonds?
The phosphate group is bonded to the C5 atom on the pentose in an individual nucleotide. Nucleotides condense together when the phosphate group on one nucleotide bonds to the C3 atom on another nucleotide to form a phosphodiester.
Nucleotides consist of a phosphate group bonded to a pentose sugar bonded to a nitrogenous base. How many different nucleotides exist naturally?
There are four possible nucleotides in DNA where the sugar is deoxyribose and the bases are C, G, A and T and there are four different possible nucleotides in RNA where the sugar is ribose and the bases are C, G, A and U.
Which base can form three hydrogen bonds with cytosine?
The complementary base pair of cytosine is guanine. Adenine only forms two hydrogen bonds with its complementary base pairs thymine and uracil.
Which sugar forms the basis of DNA?
The pentose sugar in DNA (deoxyribonucleic acid) is deoxyribose.
The sequence of nitrogenous bases in a section of DNA is -G-A-T-T-C-. What will be the sequence of bases in the complementary strand in RNA?
Cytosine and guanine are complementary pairs in both DNA and RNA but in DNA the complementary pair of adenine is thymine whereas in RNA it is uracil.
How many different codons can be produced using the triplet code?
Three nucleotides containing one of four possible nitrogenous bases gives 43 = 64 possible codons.
What are histones?
Histones are basic proteins found in the nucleus of cells which order the DNA into structural units.
What is the origin of the negative charge on DNA?
The phosphate groups in each nucleotide making up the 'backbone' of DNA contain a negative charge.
Which are associated with genetic engineering?
I. production of an exact copy of genes
II. swapping of genes between species
III. production of a unique set of genes
Producing an exact copy of genes is "cloning" not genetic engineering, although some of the same techniques are used.
The genetic codes carried by messenger RNA for the amino acids tryptophan and asparagine are UGG and AAU respectively. Tyrosine can be coded by either UAU or UAC. Which sequences of bases on DNA will be required to include −asp−tyr−trp− into the synthesis of the primary structure of a protein?
The correct sequence for -asp-tyr-trp- on RNA is either −AAU−UAU−UGG− or −AAU−UAC−UGG− so the complementary strand on DNA will be either −TTA−ATA−ACC− or −TTA−ATG−ACC−.
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