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Biology · 2024 · 5 marks
CBSE 2024 · Region 2 · Set 1 · Q32
(a) (i) Compare the pattern of inheritance of flower colour in garden pea plant (violet/white) with snapdragon plant (red/white) on the basis of the…
(i)
Compare the pattern of inheritance of flower colour in garden pea plant (violet/white) with snapdragon plant (red/white) on the basis of the following :
(1)
$\displaystyle \mathrm{F}_{1}$ phenotypic expression;
(2)
expected phenotypic and genotypic expression of $\displaystyle \mathrm{F}_{2}$ generation;
(3)
the conclusion you reached at the end of the comparison made.
(ii)
List any two characteristics of pattern of inheritance of human blood group ABO.
(i)
Draw a schematic, self-explanatory labelled diagram of lac operon in a 'switched on condition'.
(ii)
Why is regulation of lac operon referred to as negative regulation ?
Marking-scheme solution
(i)
Pea plant (Violet/White)
Snapdragon plant (Red/White)
F $\displaystyle 1$ -All violet ($\displaystyle 100$%)
F1-All pink flowers ($\displaystyle 100$%)
F2 Phenotype –
$\displaystyle 3$ : $\displaystyle 1$
Violet : white
Genotype -$\displaystyle 1$ : $\displaystyle 2$ : $\displaystyle 1$
VV : Vv : vv
F2 Phenotype -
$\displaystyle 1$ : $\displaystyle 2$ : $\displaystyle 1$
Red : pink : white ,
Genotype – $\displaystyle 1$ : $\displaystyle 2$ : $\displaystyle 1$
RR : Rr : rr.
Conclusion : Inheritance of
flower colours in pea plant
shows violet colour gene is
completely dominant over white colour gene (recessive)/ shows dominance
Whereas in snapdragon red colour gene shows incomplete dominance over white colour gene in heterozygous state/ shows incomplete dominance
(ii)
It shows multiple allelism with alleles IA, IB, i
IA, IB genes show co-dominance in blood group AB,
IA & IB shows complete dominance over i.
(i)
(ii)
Repressor binds to operator to inhibit the gene expression
All Principles of Inheritance and Variation questions2024 question paperNCERT solutions: Principles of Inheritance and VariationPractice Principles of Inheritance and Variation →
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CBSE Class 12 Biology past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.