Govt. Exams
Entrance Exams
Phenotypic plasticity is the ability of a single genotype to produce different phenotypes in response to environmental variation (e.g., hydrangea flower color).
Natural selection is the non-random differential reproduction of organisms with traits that increase fitness. Organisms with advantageous traits leave more offspring.
Silent mutation occurs in the third position of a codon and does not change the amino acid due to degeneracy of genetic code. No phenotypic effect.
Cross: XᴮXᵇ × XᴮY produces sons: 50% XᴮY (normal) and 50% XᵇY (color blind). Therefore, 50% of sons are color blind.
Haemophilia A (clotting factor VIII deficiency) is X-linked recessive. Affected males (XᵃY) pass the allele to all daughters but no sons.
X-linked recessive traits show more affected males (XᵃY) than females because males need only one copy of recessive allele on their single X chromosome.
Recessive phenotype = 360/1000 = 0.36 = q². Therefore q = √0.36 = 0.60. This represents the frequency of recessive allele.
In Hardy-Weinberg equation, p and q represent frequencies of two alleles in a population. p² and q² are homozygous frequencies; 2pq is heterozygous frequency.
The correct hierarchical order is: Nucleotide (basic unit) → DNA (polymer of nucleotides) → Gene (segment of DNA) → Chromosome (condensed DNA with proteins).
The 1:1 ratio indicates a testcross result (Rr × rr). The round seed parent must be heterozygous (Rr) to produce wrinkled (rr) offspring.
