$\begin{array}{|l|l|l|}
\hline \text{Abnormality} & \text{Cause} & \text{Characteristic} \\
\hline \begin{array}{l}
\text{Down's syndrome}
\end{array} & \begin{array}{l}
\text{Trisomy of 21st autosome} \\
(45 A + XX/XY)
\end{array} & \begin{array}{l}
\text{Mental retardation,} \\
\text{prominent head,} \\
\text{flattened nasal bridge,} \\
\text{habitually open mouth} \\
\text{and projecting lower lips}
\end{array} \\
\hline \begin{array}{l}
\text{Turner's syndrome}
\end{array} & \begin{array}{l}
\text{Non-disjunction} \\
\text{of sex chromosome} \\
\binom{2 n=45}{44 \mathrm{~A}+\mathrm{XO}}
\end{array} & \begin{array}{l}
\text{Sterile female, webbed} \\
\text{neck, no breast} \\
\text{development, no} \\
\text{menstruation or egg} \\
\text{production}
\end{array} \\
\hline \begin{array}{l}
\text{Klinefelter's syndrome}
\end{array} & \begin{array}{l}
\text{Non-disjunction} \\
\text{of sex chromosome} \\
\binom{2 n=47}{44 \mathrm{~A}+\mathrm{XXY}}
\end{array} & \begin{array}{l}
\text{Gynecomastia in males,} \\
\text{mentally defective,} \\
\text{testes underdeveloped}
\end{array} \\
\hline \begin{array}{l}
\text{Sickle cell anaemia}
\end{array} & \begin{array}{l}
\text{Molecular gene} \\
\text{mutation of gene} \\
\mathrm{Hb}^{\mathrm{A}}
\end{array} & \begin{array}{l}
\text{Sickle-shaped RBCs, do} \\
\text{not transport } \mathrm{O}_2 \\
\text{efficiently}
\end{array} \\
\hline
\end{array}$