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Biology · 2026 · 2 marks
CBSE 2026 · Region 2 · Set 1 · Q17
(a) The diagram below shows the sequence of amino acids in part of haemoglobin molecule. (i) If the base * T is substituted with A, in 'C * T T' of…
The diagram below shows the sequence of amino acids in part of haemoglobin molecule.
(i)
If the base $\displaystyle \stackrel{*}{\mathrm{~T}}$ is substituted with A, in 'C$\displaystyle \stackrel{*}{\mathrm{T}}$T' of DNA strand how would it affect the haemoglobin chain ?
(ii)
Name the condition and the effects associated with the above substitution.
DNA is considered a more stable genetic material than RNA. Justify this statement with suitable reasons.
Marking-scheme solution
(i)
Substitution of Glutamic acid by Valine at the sixth position of beta globin chain of haemoglobin molecule / Polymerisation of haemoglobin molecule under low oxygen tension
(ii)
$\displaystyle \star$ Sickle cell anaemia
$\displaystyle \star$ Change in shape of the RBC from biconcave to elongated sickle like structure / Oxygen carrying capacity of haemoglobin reduces.
$\displaystyle \star$ DNA is double stranded and the two strands being complimentary make it more stable than RNA
$\displaystyle \star$ The presence of thymine at the place of uracil confers additional stability to DNA.
$\displaystyle \star$ $\displaystyle 2$’-OH group in RNA is reactive group and makes it labile and easily degradable therefore DNA chemically is less reactive
$\displaystyle \star$ DNA being more stable mutate at slower rate than RNA
(Any Two)
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