A cross between a homozygous dominant (AA) and homozygous recessive (aa) individual produces offspring that are all:
Answer: B
AA × aa produces all Aa offspring (test cross principle). All offspring are heterozygous with dominant phenotype.
Q.62Easy
Gene mutation is defined as:
Answer: B
Mutation is a permanent change in the DNA sequence that can occur spontaneously or be induced. It is the source of genetic variation.
Q.63Easy
A cross between a homozygous tall plant (TT) and homozygous dwarf plant (tt) produces F1 generation. When F1 is self-pollinated, the ratio of tall to dwarf plants in F2 will be:
Answer: A
F1 (Tt) self-pollination gives 3 tall (TT, Tt, Tt) : 1 dwarf (tt) ratio following Mendelian monohybrid cross pattern.
Q.64Easy
A man with blood group AB marries a woman with blood group O. Their children will have blood groups:
Answer: A
Man (IAIB) × Woman (ii) produces IAi (Group A) and IBi (Group B) offspring only. O group requires ii genotype.
Q.65Easy
Which of the following evolutionary evidences is based on the study of vestigial structures like human tailbone and wisdom teeth?
Answer: B
Vestigial structures are anatomical remnants that indicate common ancestry with other organisms, supporting comparative morphology evidence.
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Q.66Easy
In pea plants, yellow seed (Y) is dominant over green (y). If a cross produces 75% yellow and 25% green seeds, what was the genotype of the parents?
Answer: B
3:1 ratio (75% yellow : 25% green) is characteristic of monohybrid cross between two heterozygotes (Yy × Yy).
Q.67Easy
A couple plans to have children. The man is a carrier for cystic fibrosis (Aa) and the woman is homozygous normal (AA). What is the probability their child will have cystic fibrosis?
Answer: A
Cross AA × Aa produces AA and Aa offspring only. Cystic fibrosis requires aa genotype, so probability is 0%.
Q.68Easy
Homologous structures in different species indicate:
Answer: B
Homologous structures are similar due to common ancestry with modification over time—classical evidence for divergent evolution.
Q.69Easy
In Drosophila, the gene for white eyes (w) is X-linked recessive. A white-eyed female is crossed with a red-eyed male. What will be the phenotype of F1 females?
Answer: A
White-eyed female (XwXw) × red-eyed male (XWY). F1 females receive Xw from mother and XW from father, making them XWXw (red-eyed carriers).
Q.70Easy
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.71Easy
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.72Easy
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.73Easy
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.74Easy
Which of the following best describes the Hardy-Weinberg equilibrium principle?
Answer: A
Hardy-Weinberg equilibrium states that allele frequencies remain constant when no evolutionary forces (mutation, selection, migration, genetic drift) act on a population.
Q.75Easy
In a dihybrid cross between AaBb × AaBb, what is the probability of obtaining aabb genotype?
Answer: A
For AaBb × AaBb, probability of aa = 41 and bb = 41. Combined probability = 41 × 41 = 161.
Q.76Easy
Which type of natural selection favors both extreme phenotypes over the intermediate phenotype?
Answer: A
Disruptive selection eliminates intermediate phenotypes and favors both extreme phenotypes, increasing genetic variation.
Q.77Easy
What is the term for the evolutionary relationship where two or more species share a common ancestor?
Answer: C
Common descent refers to the principle that all organisms share evolutionary ancestry, a fundamental concept in evolutionary biology.
Q.78Easy
Which of the following is the best evidence for evolution?
Answer: A
Homologous structures (similar structures with different functions) indicate common ancestry and provide strong anatomical evidence for evolution.
Q.79Easy
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.80Easy
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.
