Which of the following statements about mutations is INCORRECT?
Answer: B
Most mutations are either neutral or harmful; only rarely are they beneficial. This is a key principle in evolutionary biology.
Q.42Easy
A cross between two pea plants produces offspring in the ratio 1:2:1 for a particular trait. This ratio suggests:
Answer: A
1:2:1 ratio indicates Aa × Aa, where offspring are 1 AA : 2 Aa : 1 aa. This is the typical F2 ratio for a monohybrid cross.
Q.43Easy
In human genetics, the ABO blood group is determined by multiple alleles. A person with blood type AB has which genotype?
Answer: C
Type AB blood group is codominant, expressed as IAIB, where both IA and IB alleles are expressed equally.
Q.44Easy
Which evolutionary evidence involves structural similarities between embryos of different species during early development?
Answer: C
Embryological similarities, such as gill slits in vertebrate embryos, demonstrate common evolutionary ancestry among different species.
Q.45Medium
A gene has four alleles in a population. If three alleles have frequencies of 0.4, 0.3, and 0.2, what is the frequency of the fourth allele?
Answer: A
According to Hardy-Weinberg principle, total allele frequencies must equal 1. Therefore, 1 - (0.4 + 0.3 + 0.2) = 0.1
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Q.46Medium
In a population at Hardy-Weinberg equilibrium, if the frequency of recessive allele (q) = 0.3, what is the frequency of heterozygous individuals?
Answer: A
If q = 0.3, then p = 0.7. Heterozygous frequency = 2pq = 2(0.7)(0.3) = 0.42
Q.47Medium
A tall plant (genotype unknown) is crossed with a dwarf plant. All offspring are tall. What is the most likely genotype of the tall parent?
Answer: A
All offspring being tall when crossed with dwarf (tt) indicates the tall parent is TT. If it were Tt, approximately half offspring would be dwarf.
Q.48Medium
Which of the following best represents anagenesis in evolution?
Answer: B
Anagenesis refers to phyletic evolution or linear evolution where one species gradually transforms into another without branching.
Q.49Medium
A person is heterozygous for cystic fibrosis (Ff). Their partner is homozygous normal (FF). What is the probability of having an affected child?
Answer: A
Cross: Ff × FF produces FF and Ff offspring. All are phenotypically normal. Probability of affected (ff) child = 0%
Q.50Medium
In Darwin's theory of natural selection, 'variation' is important because it:
Answer: A
Variation provides the raw material for natural selection. Without variation, there would be no differential reproductive success.
Q.51Medium
A dihybrid cross (AaBb × AaBb) is performed. What is the probability of getting the recessive phenotype for both traits?
Answer: A
For AaBb × AaBb: probability of aa = 41, probability of bb = 41. Combined: 41 × 41 = 161
Q.52Medium
Antibiotic resistance in bacteria develops rapidly due to:
Answer: B
Antibiotic resistance emerges through natural selection. Resistant bacteria survive antibiotic treatment and reproduce, increasing resistance frequency in the population.
Q.53Medium
Which genetic concept explains why children of the same parents can have different traits despite inheriting genes from both?
Answer: B
Segregation of alleles and recombination during meiosis create genetic variation in offspring, leading to phenotypic differences.
Q.54Medium
A new species can be defined by reproductive isolation from other species. Which reproductive barrier is exemplified by lions and tigers producing sterile offspring (ligers)?
Answer: D
Ligers are viable hybrids but sterile, representing post-zygotic isolation where hybrids have reduced fitness or viability.
Q.55Medium
In human genetics, color blindness (red-green) is X-linked recessive. A color-blind woman has how many copies of the color-blindness allele?
Answer: B
A color-blind female must be homozygous recessive (XbXb) because she has only two X chromosomes. She has two copies of the recessive allele.
Q.56Medium
Microevolution differs from macroevolution primarily in that microevolution:
Answer: B
Microevolution involves allele frequency changes within a population over relatively short periods. Macroevolution is long-term divergence into new species.
Q.57Medium
A heterozygous red-eyed Drosophila female (XAXa) is crossed with a white-eyed male (XaY). What percentage of male offspring will have white eyes?
Answer: B
Cross: XAXa (female) × XaY (male). Male offspring: 21 XAY (red) and 21 XaY (white). Therefore, 50% white-eyed males.
Q.58Medium
A point mutation in a gene's coding sequence results in UAA instead of CAA. This type of mutation is called:
Answer: C
UAA is a stop codon. A missense mutation creating a stop codon is called a nonsense mutation, resulting in premature protein termination.
Q.59Hard
Gene flow between two populations can prevent genetic drift from causing fixation of alleles because:
Answer: A
Gene flow (migration) introduces alleles from one population to another, counteracting genetic drift and maintaining genetic variation.
Q.60Hard
A three-point testcross in Drosophila yields recombinant classes with lower frequencies than parental classes. This demonstrates:
Answer: B
Lower recombinant frequencies indicate genes are linked but can undergo crossing over, producing recombinants at lower frequencies than parentals.
