Govt. Exams
Entrance Exams
Bottlenecks drastically reduce population size, increasing genetic drift. Random allele loss occurs, reducing genetic variation and increasing chance of fixation.
Darwin's finches underwent adaptive radiation, diverging from a common ancestor into multiple species with different beak morphologies adapted to different food sources.
Cross: AS × AS produces AA (unaffected, 1/4), AS (carrier, 1/2), SS (affected, 1/4). Probability of unaffected = 1/4 + 1/2 = 3/4 = 0.75
If one dominant homozygous class (AABB, AABb, or AAbb) is lethal, the 9:3:3:1 ratio adjusts accordingly. Common outcome is 9:3:4 when one class is removed.
Lower recombinant frequencies indicate genes are linked but can undergo crossing over, producing recombinants at lower frequencies than parentals.
Gene flow (migration) introduces alleles from one population to another, counteracting genetic drift and maintaining genetic variation.
Recessive frequency = 400/50,000 = 0.008 = q². Thus q = √0.008 ≈ 0.089. Therefore p = 1 - 0.089 ≈ 0.911 ≈ 0.9 (Option should read 0.9, but closest match is A: 0.8 or recalculate: q² = 0.008, q ≈ 0.09, p ≈ 0.91). If recessive phenotype frequency is 0.008, then q = 0.089, p = 0.911.
Carrier mother (XBXb) × Color-blind father (XbY) produces: XBXb (carrier daughter), XbXb (color-blind daughter), XBY (normal son), XbY (color-blind son). 50% of daughters (1 out of 2) have normal vision.
Pre-existing resistant bacteria survive antibiotic exposure while susceptible ones die, increasing resistant population frequency—natural selection.
Loss of an entire chromosome causes imbalance in gene dosage affecting multiple essential genes, making it almost always lethal.
