Govt Exams
Allopatric speciation begins with geographic isolation, followed by independent genetic drift and mutations in isolated populations, leading to reproductive isolation and eventually new species formation.
Heterozygous female (X^W X^w) × normal male (X^W Y) produces X^W X^W and X^W X^w females, both with normal eyes. White eyes appear only in males (X^w Y) at 50%.
A bottleneck reduces population size dramatically, causing random loss of alleles and making genetic drift the dominant evolutionary force, reducing genetic variation.
Without crossing over, the number of different gamete types = 2^n, where n = number of heterozygous gene pairs = 2^5 = 32.
Random assortment of chromosomes during meiosis doesn't change allele frequencies; it only creates different combinations. Selection, drift, and gene flow all change frequencies.
Total individuals = 1000. p = (200+300)/2000 = 0.25, q = 0.75. Expected: BB = 62.5, Bb = 375, bb = 562.5. Observed shows excess homozygotes, indicating inbreeding or population substructure.
Interference = 1 - Coefficient of Coincidence = 1 - 0.8 = 0.2. This measures how much one crossover interferes with adjacent crossovers.
In small populations, genetic drift can cause alleles to be randomly lost. With frequency only 0.02 in a population of 100, the allele is vulnerable to random loss.
Homologous structures (similar structures with different functions) indicate common ancestry and provide strong anatomical evidence for evolution.
Frameshift mutations shift the reading frame for all downstream codons, typically resulting in nonfunctional proteins or premature termination.