CBSE 2024 · Region 2 · Set 1 · Q32 · 5 marks
(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 ?
(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
Principles of Inheritance and VariationInheritance of One GeneAnalyselong_answerhard
Practice Principles of Inheritance and Variation →All Principles of Inheritance and Variation questions
More from Principles of Inheritance and Variation
- Using a Punnett square workout the distribution of an autosomal phenotypic feature in the first filial…2025 · asked 3×
- By using Punnett square depict the genotypes and phenotypes of test crosses (where green pod colour (G) is…2023 · asked 3×
- Assertion: In dihybrid crosses involving sex-linked genes in Drosophila generation of non-parental gene…2025 · asked 3×
- The following pedigree chart shows the inheritance of a genetic disorder up to three generations of a family.…2023 · asked 3×
- Write the types and locations of the genes causing thalassemia in humans. State the cause and symptoms of the…2026 · asked 3×
- A person with trisomy of 21^ st chromosome shows (i) Furrowed tongue (ii) Characteristic palm crease (iii)…2024 · asked 3×
- The chromosome number is fixed for all normal organisms leading to species specification whereas any…2023 · asked 3×
- A student performed some crosses in plants and represented the result in the form of bar graphs as shown…2026 · asked 3×
CBSE Class 12 Biology past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.