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Biology · 2024 · 3 marks
CBSE 2024 · Region 5 · Set 2 · Q26
Expression of different genes for different traits may show dominance, incomplete dominance or co-dominance. Write about expression of such genes…
Expression of different genes for different traits may show dominance, incomplete dominance or co-dominance. Write about expression of such genes with the help of one example each. 27. (a) Tropical regions harbour more species than the temperate regions. How have biologists tried to explain this in their own ways? Explain.
(b)
What does an ecological pyramid represent ?
(ii)
The Ecological pyramids may have an 'upright' or an 'inverted' shape. Justify with the help of suitable examples. 28. Identify a, b, c, d, e and f in the table given below :
| Sl. No. | Organism | Bioactive Molecule | Use |
| 1. | Monascus purpureus | a | b |
| 2. | c | d | Antibiotic |
| 3. | e | Cyclosporin A | f |
Marking-scheme solution
Dominance:
In a dissimilar pair of factors or alleles one member of the pair expresses itself and is called dominant
Example: Pea plant/ Pisum sativum
P TT x tt
Tall Dwarf
F1 Tt
(All Tall)
T is dominant over t
Incomplete dominance
In F1 phenotype did not resemble either of the two parents or exhibited a intermediate character of the two called incomplete
Example: Snapdragon/ Dog flower/ Antirrhinum sp.
P
RR x rr
Red White
F1 Rr
All Pink/intermediate
Co-dominance
Example: ABO Blood groups in human beings,
Dominant genes A and B are expressed together in AB blood group
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