1. Draw a diagram of a DNA nucleotide.
Answer
2. Which component of a nucleotide contains nitrogen ?
Answer
The base.
3. Name the bond formed between two adjacent nucleotides.
Answer
Phosphodiester bonds.
4. Scientists grew E. coli in heavy nitrogen, so all DNA was heavy (generation 0). They then transferred the bacteria to light nitrogen. After one replication (generation 1) and two replications (generation 2), DNA was centrifuged to form bands by density. The figure below shows some possible results from this investigation. Explain which of these results shows that DNA replicates semi-conservatively.
Answer
B, because the second generation has a middle (and top) band. The middle band contains DNA composed of one heavy and one light strand, showing one "old" and one "new" strand.
5. The figure below shows part of a DNA molecule. Name components X and Y.
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6. How many nucleotides there are in the figure above ?
Answer
There are 8 nucleotides.
7. Women who are taking gemcitabine are warned that they should not become pregnant. Explain why.
Answer
Embryo cells divide frequently. Gemcitabine inhibits DNA replication and mitosis in all cells, so the embryo would not develop properly and there is a risk of birth defects.
8. Give three structural differences between DNA and RNA.
Answer
RNA has ribose and DNA has deoxyribose. RNA has uracil and DNA has thymine. RNA is single stranded and DNA is double stranded.