Auto assign points/marks to Multiple Choice Questions

Question

I am creating an exam with both multiple choice questions and structured questions. How do i automatically assign one mark or one point to multiple choice questions so that when i compile the paper the total number of marks includes that of multiple choice questions.

if i use this code, i get the following

\documentclass[12pt,addpoints,answers]{exam}
\begin{document}

This exam has \numquestions\ questions, for a total of \numpoints\  points.
\begin{questions}
\question What is the function of nucleoli?
\begin{choices}
    \choice the formation and breakdown of the nuclear envelope
    \choice the formation of centromeres
    \choice the formation of ribosomes
    \choice the organisation of the spindle during nuclear division
\end{choices}   
\question An actively growing cell is supplied with radioactive amino acids.\\
Which cell component would first show an increase in radioactivity? \\
\begin{oneparchoices}
    \choice Golgi body
    \choice mitochondrion
    \choice nucleus
    \choice rough endoplasmic reticulum
\end{oneparchoices}
    \question \begin{parts}
        \part There are 20 units of DNA in a cell during stage G2 of mitosis. Give the number of units of DNA   you would expect to find in this cell
        \begin{subparts}
            \subpart[1] at prophase of mitosis; \fillwithdottedlines{0.25in}
        \end{subparts}
    \end{parts}
    \end{questions}
\end{document}

Answer 1

I modified \question to default to 1 point, so you have to use \question[0] to assign points by parts. I couldn't find an option to suppress printing points, so I used \pointformat to create one.

\documentclass[12pt,addpoints,answers]{exam}

\begin{document}

This exam has \numquestions\ questions, for a total of \numpoints\  points.
\begin{questions}
\let\normalquestion=\question
\renewcommand{\question}[2][1]{\normalquestion[#1]#2}
\pointformat{\hspace{-.5em}}

\question What is the function of nucleoli?
\begin{choices}
    \choice the formation and breakdown of the nuclear envelope
    \choice the formation of centromeres
    \choice the formation of ribosomes
    \choice the organisation of the spindle during nuclear division
\end{choices}   
\question An actively growing cell is supplied with radioactive amino acids.\\
Which cell component would first show an increase in radioactivity? \\
\begin{oneparchoices}
    \choice Golgi body
    \choice mitochondrion
    \choice nucleus
    \choice rough endoplasmic reticulum
\end{oneparchoices}
    \question[0] \begin{parts}
        \part There are 20 units of DNA in a cell during stage G2 of mitosis. Give the number of units of DNA   you would expect to find in this cell
        \begin{subparts}
            \subpart[1] at prophase of mitosis; \fillwithdottedlines{0.25in}
        \end{subparts}
    \end{parts}
    \end{questions}
\end{document}