A new allele arises in a small island population of 100 individuals. The allele frequency is 0.02. Over the next 10 generations without selection, what is most likely to happen?
Answer: A
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.
Q.282Hard
In a three-point testcross involving genes A, B, and C with map distances A-B = 10 map units and B-C = 20 map units, if coefficient of coincidence is 0.8, what is the interference value?
Answer: A
Interference = 1 - Coefficient of Coincidence = 1 - 0.8 = 0.2. This measures how much one crossover interferes with adjacent crossovers.
Q.283Hard
A researcher observes that in a population of snails, shell color is controlled by a single gene with two alleles (B and b). Yellow shells (BB) = 100, Brown shells (Bb) = 300, White shells (bb) = 600. Is this population in Hardy-Weinberg equilibrium?
Answer: B
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.
Q.284Hard
Which of the following would NOT cause a change in allele frequencies in a population?
Answer: B
Random assortment of chromosomes during meiosis doesn't change allele frequencies; it only creates different combinations. Selection, drift, and gene flow all change frequencies.
Q.285Hard
A species shows 5 pairs of chromosomes. During meiosis in an individual heterozygous for all 5 genes (AaBbCcDdEe), what is the maximum number of different gamete types that can be produced?
Answer: C
Without crossing over, the number of different gamete types = 2^n, where n = number of heterozygous gene pairs = 2^5 = 32.
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Q.286Hard
In a population affected by a recent bottleneck event, which is most likely to occur?
Answer: C
A bottleneck reduces population size dramatically, causing random loss of alleles and making genetic drift the dominant evolutionary force, reducing genetic variation.
Q.287Easy
In Drosophila, the white eye mutation is X-linked recessive. If a heterozygous female is crossed with a normal male, what percentage of female offspring will have white eyes?
Answer: A
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%.
Q.288Easy
Which of the following represents the correct sequence of events during the evolution of a new species through allopatric speciation?
Answer: A
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.
Q.289Easy
A population of 500 individuals has allele frequencies of A = 0.7 and a = 0.3. If the population follows Hardy-Weinberg equilibrium, what will be the frequency of heterozygotes in the next generation?
Answer: B
Using Hardy-Weinberg equation: frequency of Aa = 2pq = 2(0.7)(0.3) = 0.42. This remains constant across generations in equilibrium.
Q.290Medium
A silent mutation in the third codon position of a gene coding for protein synthesis most likely occurs due to:
Answer: A
The wobble hypothesis explains how changes in the third codon position often don't change the amino acid due to the degeneracy of the genetic code, resulting in silent mutations.
Q.291Medium
In a testcross of a dihybrid (AaBb) with a homozygous recessive (aabb), if the offspring ratio deviates from 1:1:1:1, it indicates:
Answer: B
A 1:1:1:1 ratio indicates independent assortment. Deviation suggests the genes are linked on the same chromosome, with recombination occurring at a frequency less than 50%.
Q.292Medium
Peppered moths in industrial England showed rapid evolution from predominantly light-colored to dark-colored populations. This is an example of:
Answer: A
Industrial pollution darkened tree bark, favoring dark moths through directional selection. This is a classic example of evolution in response to environmental change.
Q.293Medium
A mutation converts an amino acid codon (GUU for valine) to a stop codon (UAA). This type of mutation would most severely affect the protein by:
Answer: B
A nonsense mutation (codon to stop codon) causes premature termination of translation, resulting in a truncated, usually nonfunctional protein. This is more severe than missense mutations.
Q.294Easy
Homologous structures like bat wings, whale flippers, and human arms demonstrate evolutionary relationship through:
Answer: B
These structures share similar bone arrangements despite different functions, indicating descent from a common ancestor with modification—evidence for divergent evolution.
Q.295Medium
In a cross between two heterozygous individuals (Aa × Aa), if the homozygous dominant genotype (AA) is lethal and dies in utero, the surviving offspring ratio would be:
Answer: B
Aa × Aa normally produces 1 AA : 2 Aa : 1 aa. If AA is lethal, only Aa and aa survive in a 2:1 ratio.
Q.296Hard
A researcher studying gene expression notices that identical twins show different phenotypes for a trait despite having identical genotypes. This is most likely due to:
Answer: A
Epigenetic changes (DNA methylation, histone modifications) and differential environmental exposure can cause phenotypic differences in genetically identical individuals.
Q.297Hard
In genomic imprinting, a disorder appears only when the mutant allele is inherited from the father but not the mother. This pattern suggests:
Answer: D
Genomic imprinting involves parent-specific gene silencing. If only the paternal mutation causes disease, it indicates the maternal allele is normally silenced (imprinted), making the paternal allele the only functional copy.
Q.298Easy
Which hormone is primarily responsible for the regulation of spermatogenesis in males?
Answer: A
Testosterone, produced by Leydig cells in testes, is the primary hormone regulating spermatogenesis. It acts on Sertoli cells and is essential for sperm production.
Q.299Easy
The menstrual cycle in humans is approximately how many days?
Answer: B
The average menstrual cycle is 28 days, though it can range from 21-35 days. It consists of menstruation, follicular phase, ovulation, and luteal phase.
Q.300Easy
Which intrauterine device (IUD) releases hormones to prevent pregnancy?
Answer: B
Levonorgestrel-releasing IUDs (like Mirena) release the hormone levonorgestrel, which thickens cervical mucus and prevents fertilization, with added uterine effects.
