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STD 12 - 4. principal of inheritance and variation — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYSTD 12 - 4. principal of inheritance and variation1 Mark
MCQ
Sickle­cell anaemia is
  • A
    caused by substitution of valine by glutamic acid in the beta globin chain of haemoglobin
  • ✓
    caused by a change in a single base pair of $DNA$
  • C
    characterized by elongated sickle like $RBCs$ with a nucleus
  • D
    an autosomal linked dominant trait.
✓

Answer

Correct option: B.
caused by a change in a single base pair of $DNA$
b
(b) : Sickle­cell anaemia is an autosomal hereditary Yellow green disorder in which erythrocytes become sickle shaped. It is caused by the formation ofabnormal haemoglobin called haemoglobin­-$S$. Haemoglobin­-$S$ is formed when $6^{th}$ amino acid of $\beta$-­chain, $i.e.$, glutamic acid is replaced by valine due to substitution. It occurs due to a single nucleotide change $(A → T)$ in the $\beta$-­globin gene of coding strand. In the normal $\beta$-­globin gene the $DNA$ sequence is $CCTGAGGAG$, while in sickle­ cell anaemia, the sequence is $CCTGTGGAG.$

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