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BIOLOGY, M5 2025 HSC 19 MC

The grasshopper has an average genome size of 120 million base pairs. 42% of these base pairs contain cytosine and guanine.

What is the number of DNA nucleotides with a thymine base found in each cell?

  1. 25.2 million
  2. 34.8 million
  3. 69.6 million
  4. 120 million
Show Answers Only

\(C\)

Show Worked Solution
  • C is correct: If 42% are C+G, then 58% are A+T; thymine is 29% of 240 million nucleotides.

Other Options:

  • A is incorrect: This calculates as 21% instead of 29% of total nucleotides.
  • B is incorrect: This calculates as 29% of base pairs, not total nucleotides.
  • D is incorrect: This is the total number of base pairs, not thymine nucleotides.

Filed Under: DNA and Polypeptide Synthesis Tagged With: Band 6, smc-3650-70-DNA Components

BIOLOGY, M5 2024 HSC 4 MC

Which row of the table correctly identifies components of DNA?

\begin{align*}
\begin{array}{l}
\rule{0pt}{2.5ex} \ \rule[-1ex]{0pt}{0pt}& \\
\rule{0pt}{2.5ex}\textbf{A.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{B.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{C.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{D.}\rule[-1ex]{0pt}{0pt}\\
\end{array}
\begin{array}{|c|c|}
\hline
\rule{0pt}{2.5ex}\textit{Phosphate} \rule[-1ex]{0pt}{0pt}& \quad \textit{Ribose} \quad & \textit{Deoxyribose} & \quad \textit{Uracil} \quad & \ \ \textit{Thymine}\ \ \\
\hline
\rule{0pt}{2.5ex}\checkmark \rule[-1ex]{0pt}{0pt}& \text{} & \checkmark & \checkmark & \text{} \\
\hline
\rule{0pt}{2.5ex}\text{} \rule[-1ex]{0pt}{0pt}& \checkmark & \text{} & \checkmark & \checkmark \\
\hline
\rule{0pt}{2.5ex}\text{} \rule[-1ex]{0pt}{0pt}& \checkmark & \checkmark & \text{} & \checkmark \\
\hline
\rule{0pt}{2.5ex}\checkmark \rule[-1ex]{0pt}{0pt}& \text{} & \checkmark & \text{} & \checkmark \\
\hline
\end{array}
\end{align*}

Show Answers Only

\(D\)

Show Worked Solution
  • DNA contains phosphate groups, deoxyribose sugar (not ribose), and thymine (not uracil which is found in RNA instead).
  • The last row with checkmarks for phosphate, deoxyribose, and thymine is therefore the only correct combination.

\(\Rightarrow D\)

Filed Under: DNA and Polypeptide Synthesis Tagged With: Band 3, smc-3650-70-DNA Components

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