Population Genetics Notes

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### Objective Questions (with Answers) - BSc Level (उद्देश्य प्रश्न - उत्तर सहित) 1. What is the primary focus of **population genetics**? a) Individual gene expression b) Genetic composition of populations and changes in gene frequencies c) Cellular genetics d) Organismal development **Answer: b) Genetic composition of populations and changes in gene frequencies** 2. A **Mendelian population** is characterized by: a) A group of organisms sharing a common habitat but not interbreeding. b) A reproductive community of sexual individuals sharing a common gene pool. c) A collection of individuals with identical genotypes. d) A population undergoing rapid evolution. **Answer: b) A reproductive community of sexual individuals sharing a common gene pool.** 3. Which of the following is **NOT** an assumption of the **Hardy-Weinberg Law**? a) Large population size b) Random mating c) High mutation rate d) Absence of natural selection **Answer: c) High mutation rate** 4. The Hardy-Weinberg equation $p^2 + 2pq + q^2 = 1$ represents the frequencies of: a) Alleles b) Genotypes c) Phenotypes d) Mutations **Answer: b) Genotypes** 5. If the frequency of allele 'A' (p) is 0.7 in a population, and the population is in Hardy-Weinberg equilibrium, what is the frequency of the homozygous recessive genotype 'aa' ($q^2$)? a) 0.49 b) 0.42 c) 0.09 d) 0.3 **Answer: c) 0.09 (If $p=0.7$, then $q=1-0.7=0.3$. So $q^2 = (0.3)^2 = 0.09$)** 6. **Genetic polymorphism** is defined by the occurrence of two or more distinct forms of a species in the same habitat, where the rarest form is not maintained merely by: a) Genetic drift b) Recurrent mutation c) Gene flow d) Natural selection **Answer: b) Recurrent mutation** 7. Which type of polymorphism is maintained by natural selection favoring heterozygotes? a) Transient polymorphism b) Balanced polymorphism c) Environmental polymorphism d) Recessive polymorphism **Answer: b) Balanced polymorphism** 8. The resistance to malaria in individuals heterozygous for the sickle-cell gene is a classic example of: a) Genetic drift b) Negative selection c) Heterozygote advantage d) Assortative mating **Answer: c) Heterozygote advantage** 9. Which of the following factors would **NOT** disturb Hardy-Weinberg equilibrium? a) Random mating b) Genetic drift c) Mutation d) Gene flow **Answer: a) Random mating** 10. **Consanguinity** primarily leads to an increase in: a) Heterozygosity b) Homozygosity c) Gene flow d) Mutation rates **Answer: b) Homozygosity** 11. The term "**inbreeding depression**" refers to: a) Increased fitness due to outbreeding. b) Deterioration in fitness due to increased homozygosity from inbreeding. c) A decrease in population size due to migration. d) The loss of genetic diversity in a large population. **Answer: b) Deterioration in fitness due to increased homozygosity from inbreeding.** 12. The "**Founder Effect**" is a specific type of: a) Gene flow b) Mutation c) Genetic drift d) Natural selection **Answer: c) Genetic drift** 13. The concept that a population's average fitness is reduced due to the presence of deleterious alleles is known as: a) Genetic equilibrium b) Heterosis c) Genetic load d) Polymorphism **Answer: c) Genetic load** 14. What is the effect of **gene flow (migration)** on allele frequencies between populations? a) It makes populations more genetically distinct. b) It increases the rate of mutation. c) It makes populations more genetically similar. d) It only affects phenotypic frequencies. **Answer: c) It makes populations more genetically similar.** 15. **Assortative mating** is a form of: a) Random mating b) Non-random mating c) Outbreeding d) Genetic drift **Answer: b) Non-random mating** 16. If a population experiences a drastic reduction in size due to an environmental disaster, this is an example of: a) Gene flow b) Bottleneck effect c) Founder effect d) Mutation pressure **Answer: b) Bottleneck effect** 17. Which genetic phenomenon is characterized by "**hybrid vigor**"? a) Inbreeding depression b) Heterosis c) Genetic load d) Genetic drift **Answer: b) Heterosis** 18. Which of the following is **NOT** a form of variation excluded from the definition of genetic polymorphism? a) Geographical races b) Continuous variation under multifactorial control c) Rare recessive conditions eliminated by selection d) Balanced polymorphism due to heterozygote advantage **Answer: d) Balanced polymorphism due to heterozygote advantage** 19. If allele frequencies remain constant over generations, a population is said to be in: a) Genetic drift b) Gene flow c) Hardy-Weinberg equilibrium d) Mutation pressure **Answer: c) Hardy-Weinberg equilibrium** 20. The concept of "**clines**" refers to: a) Random changes in gene frequencies. b) Gradual changes in allele frequencies across geographical areas. c) The establishment of a new population by a few individuals. d) The increase in homozygosity due to inbreeding. **Answer: b) Gradual changes in allele frequencies across geographical areas.** 21. What is the definition of a **gene pool**? a) The sum of all genes in a single individual. b) The total collection of genes and their alleles within a population. c) A specific locus on a chromosome. d) The set of genes responsible for a particular phenotype. **Answer: b) The total collection of genes and their alleles within a population.** 22. The term "**panmixis**" means: a) Selection favoring a specific genotype. b) Mating between close relatives. c) Random mating. d) Migration of individuals between populations. **Answer: c) Random mating.** 23. Which of the following conditions is an example of a **balanced polymorphism** in human populations? a) Albinism b) Huntington's chorea c) Sickle-cell anemia in malaria-endemic regions d) Height variation **Answer: c) Sickle-cell anemia in malaria-endemic regions** 24. What is the expected frequency of the heterozygous genotype (Aa) in a Hardy-Weinberg equilibrium if the frequencies of A and a are p and q, respectively? a) $p^2$ b) $q^2$ c) $2pq$ d) $p+q$ **Answer: c) $2pq$** 25. If the frequency of the 'A' allele (p) is 0.6, what is the frequency of the 'a' allele (q) in a two-allele system? a) 0.6 b) 0.4 c) 0.36 d) 0.24 **Answer: b) 0.4** 26. The increase in the proportion of homozygotes in a population is a main genetic consequence of: a) Outbreeding b) Gene flow c) Inbreeding d) Negative assortative mating **Answer: c) Inbreeding** 27. What is a long-term genetic consequence of high-energy radiation exposure? a) Immediate radiation sickness b) Increased genetic load in future generations c) Enhanced reproductive rates d) Reduced mutation rates **Answer: b) Increased genetic load in future generations** 28. What did Dobzhansky define a Mendelian population as? a) A group of individuals living in isolation. b) A reproductive community of sexual and cross-fertilizing individuals sharing a common gene pool. c) A population where panmixis always occurs. d) A population with constant allele frequencies. **Answer: b) A reproductive community of sexual and cross-fertilizing individuals sharing a common gene pool.** 29. In the context of population genetics, "**microevolution**" reflects: a) Large-scale evolutionary changes over geological time. b) Changes in allele frequencies within populations. c) The origin of new species. d) The process of domestication. **Answer: b) Changes in allele frequencies within populations.** 30. The ability to taste phenyl-thio-carbamide (PTC) in humans is an example of: a) A rare recessive trait. b) A continuous variation. c) A genetic polymorphism. d) A trait affected by genetic drift only. **Answer: c) A genetic polymorphism.** 31. Which mating type involves choosing partners who share characteristics like height or intelligence? a) Random mating b) Consanguineous mating c) Assortative mating d) Outbreeding **Answer: c) Assortative mating** 32. A population where a few individuals leave a community to start a new settlement, potentially leading to different allele frequencies by chance, is an example of: a) Gene flow b) Bottleneck effect c) Founder effect d) Mutation pressure **Answer: c) Founder effect** 33. The term for marriages between blood relatives who have at least one common ancestor is: a) Assortative mating b) Panmixia c) Consanguinity d) Outbreeding **Answer: c) Consanguinity** 34. Which of these is a major category of genetic polymorphisms commonly found in human populations? a) Blood-cell antigens (blood groups) b) Eye color (often polygenic) c) Hair texture (often polygenic) d) Fingerprint patterns (complex inheritance) **Answer: a) Blood-cell antigens (blood groups)** 35. What is the main genetic consequence of **inbreeding**? a) Decrease in homozygosity b) Increase in heterozygosity c) Increase in the proportion of homozygotes d) Decrease in mutation rate **Answer: c) Increase in the proportion of homozygotes** 36. If a population is in Hardy-Weinberg equilibrium, the allele frequencies will: a) Increase over generations. b) Decrease over generations. c) Remain constant over generations. d) Fluctuate randomly. **Answer: c) Remain constant over generations.** 37. The phenomenon where traits like fertility decrease in an inbred stock is called: a) Hybrid vigor b) Genetic load c) Inbreeding depression d) Genetic drift **Answer: c) Inbreeding depression** 38. What is "**heterosis**"? a) The loss of genetic diversity. b) The increase in homozygosity. c) Hybrid vigor, leading to increased size and fertility in hybrids. d) A type of non-random mating. **Answer: c) Hybrid vigor, leading to increased size and fertility in hybrids.** 39. Which of the following is **NOT** an evolutionary force that can disturb Hardy-Weinberg equilibrium? a) Mutation b) Gene flow c) Random mating d) Natural selection **Answer: c) Random mating** 40. According to Ford (1940), genetic polymorphism occurs when distinct forms exist in such proportions that the rarest form is not maintained merely by: a) Genetic drift b) Natural selection c) Recurrent mutation d) Gene flow **Answer: c) Recurrent mutation** 41. The "**genetic load**" of a species is a measure of: a) The average fitness of the population. b) The reduction in average fitness due to deleterious alleles. c) The rate of mutation. d) The extent of gene flow. **Answer: b) The reduction in average fitness due to deleterious alleles.** 42. What is the effect of genetic damage from radiation on future generations? a) It improves their fitness. b) It can inflict harm for many generations. c) It only affects the exposed persons. d) It has no genetic consequences. **Answer: b) It can inflict harm for many generations.** 43. If the frequency of the homozygous dominant genotype (AA) is $p^2$, and the homozygous recessive genotype (aa) is $q^2$, what is the fundamental relationship between p and q? a) $p = q$ b) $p + q = 1$ c) $p - q = 1$ d) $p = 2q$ **Answer: b) $p + q = 1$** 44. What is the term for a gradual change in allele frequencies across geographical areas? a) Genetic drift b) Founder effect c) Cline d) Bottleneck effect **Answer: c) Cline** 45. Which type of mating involves individuals choosing partners regardless of their genotype? a) Assortative mating b) Consanguineous mating c) Random mating d) Inbreeding **Answer: c) Random mating** 46. What did the development of modern biochemical techniques reveal about human populations? a) Uniformity in all genetic systems. b) Wide individual and population differences in enzyme and protein systems. c) That all populations are in Hardy-Weinberg equilibrium. d) That mutation rates are constant across all genes. **Answer: b) Wide individual and population differences in enzyme and protein systems.** 47. What specific type of consanguineous marriage is often found in some Middle Eastern societies? a) First cousin marriage (FaFaSiDa) b) Parallel cousins (father's brother's daughter) c) Uncle-niece unions d) Cross cousins (mother's brother's daughter) **Answer: b) Parallel cousins (father's brother's daughter)** 48. The "**ideal**" population assumed under Hardy-Weinberg Law is essentially: a) A real population undergoing evolution. b) A mathematical abstraction or null model. c) A small, isolated community. d) A population with high mutation rates. **Answer: b) A mathematical abstraction or null model.** 49. The process of alleles spreading slowly across a racial or geographical boundary due to migration and intermarriage is known as: a) Genetic drift b) Mutation c) Gene flow d) Selection **Answer: c) Gene flow** 50. In a **balanced polymorphism**, a disease-causing allele persists because: a) It is always dominant. b) Heterozygotes resist a certain infectious illness or environmental condition. c) It has no effect on fitness. d) It is constantly introduced by mutation. **Answer: b) Heterozygotes resist a certain infectious illness or environmental condition.** 51. What is the primary role of the Hardy-Weinberg formula in population analysis? a) To directly measure evolution. b) To provide a standard against which genetic change can be measured. c) To predict individual genotypes. d) To identify new mutations. **Answer: b) To provide a standard against which genetic change can be measured.** 52. Which of these is a delayed effect of radiation damage on an individual? a) Radiation burns b) Radiation sickness c) Malignant growths (cancers) d) Immediate death **Answer: c) Malignant growths (cancers)** 53. What is the main characteristic of a **population isolate**? a) Individuals randomly mate with any external population. b) Marriage alliance is restricted within that endogamous group. c) High rates of gene flow. d) A population with no genetic variation. **Answer: b) Marriage alliance is restricted within that endogamous group.** 54. The study of human genetics is often subdivided into areas such as medical genetics, biochemical genetics, and: a) Astrophysics b) Paleontology c) Population genetics d) Oceanography **Answer: c) Population genetics** 55. What are considered the "**cornerstone**" of the modern science of genetics? a) Genetic drift b) Mendelian laws of inheritance c) Gene flow d) Hardy-Weinberg law **Answer: b) Mendelian laws of inheritance** 56. If a population is said to be in equilibrium according to the Mendelian population concept, what condition must be met regarding mating? a) Strong assortative mating b) Random choice of partners (panmixis) c) Consanguineous mating d) Negative assortative mating **Answer: b) Random choice of partners (panmixis)** 57. What is the meaning of "**genetic load**" in terms of population fitness? a) The increase in fitness due to beneficial mutations. b) The fraction by which average population fitness is decreased compared to the highest fitness genotype. c) The total number of genes in a population. d) The resistance of a population to disease. **Answer: b) The fraction by which average population fitness is decreased compared to the highest fitness genotype.** 58. Which type of marriage is defined as between individuals of opposite sex who do not have a known common ancestor? a) Consanguineous marriage b) Assortative marriage c) Inbred marriage d) Non-consanguineous marriage **Answer: d) Non-consanguineous marriage** 59. The term for the tendency of human beings to choose partners who share characteristics is: a) Random mating b) Consanguinity c) Assortative mating d) Outbreeding **Answer: c) Assortative mating** 60. What is the effect of widespread consanguinity in a community on the frequency of affected homozygotes for recessive disorders? a) Relative decrease b) No change c) Relative increase d) It eliminates them **Answer: c) Relative increase** 61. Which of the following is considered an **incest taboo** in most human societies? a) First cousin marriage b) Parent-offspring marriage c) Uncle-niece marriage d) Second cousin marriage **Answer: b) Parent-offspring marriage** 62. What did Allison (1954) discover about the **sickle-cell trait** in heterozygotes? a) It causes severe anemia in heterozygotes. b) It confers marked immunity against malaria. c) It is a rare recessive condition. d) It is an example of continuous variation. **Answer: b) It confers marked immunity against malaria.** 63. What is the typical effect of inbreeding on overall general size and fertility in animal stocks? a) Increase b) No change c) Decrease d) It varies unpredictably **Answer: c) Decrease** 64. The genetic effects of inbreeding are most similar to: a) Negative assortative mating. b) Gene flow. c) Positive assortative mating. d) Genetic drift. **Answer: c) Positive assortative mating.** 65. Which of the following genetic disorders are encountered with greater frequency in consanguineous marriages? a) Common colds b) Albinism and alkaptonuria (recessive disorders) c) Malaria (infectious disease) d) Height variations (polygenic) **Answer: b) Albinism and alkaptonuria (recessive disorders)** 66. Why is polymorphism generally **not** maintained environmentally? a) Environmental factors are too stable. b) Genetic factors are always dominant. c) Polymorphism is fundamentally a genetic condition, not environmental. d) Environmental changes are too rapid. **Answer: c) Polymorphism is fundamentally a genetic condition, not environmental.** 67. What is the role of **mutation** in altering genotype frequencies? a) It only decreases frequencies. b) It only increases frequencies. c) It introduces new alleles into the population. d) It stabilizes frequencies. **Answer: c) It introduces new alleles into the population.** 68. The concept that allele frequencies stay constant over generations is central to: a) Microevolution b) Macroevolution c) Hardy-Weinberg equilibrium d) Genetic mutation **Answer: c) Hardy-Weinberg equilibrium** 69. If the frequency of the 'AA' genotype is $p^2$, and the frequency of the 'aa' genotype is $q^2$, what is the frequency of the 'Aa' genotype? a) $p^2 + q^2$ b) $p+q$ c) $2pq$ d) $(p+q)^2$ **Answer: c) $2pq$** 70. What defines a "**breeding population**"? a) All individuals in a geographical area. b) The actual progenitors (parents) in a population that produce offspring. c) A population free from evolutionary forces. d) A group of organisms from different species. **Answer: b) The actual progenitors (parents) in a population that produce offspring.** 71. What is the primary cause of **genetic drift**? a) Large population size b) Random statistical fluctuation in small populations c) Directed migration d) Strong natural selection **Answer: b) Random statistical fluctuation in small populations** 72. Which of the following is a condition for a Mendelian population to be in **Hardy-Weinberg equilibrium**? a) Strong natural selection b) Assortative mating c) Large population size d) High mutation rate **Answer: c) Large population size** 73. The "**genetic load**" can be broadly understood as: a) Increased average fitness. b) Decreased average fitness due to harmful genes. c) The number of successful offspring. d) The rate of gene flow. **Answer: b) Decreased average fitness due to harmful genes.** 74. What is the effect of **gene flow** on genetic differences **between** populations? a) It increases genetic differences. b) It reduces genetic differences. c) It has no effect. d) It only affects phenotypic differences. **Answer: b) It reduces genetic differences.** 75. The rediscovery of Mendelian Principles in 1900 was primarily attributed to: a) Charles Darwin b) G.H. Hardy and W. Weinberg c) de Vries, Correns, and Von Tschermak d) Sewall Wright and R.A. Fisher **Answer: c) de Vries, Correns, and Von Tschermak** 76. Why is direct analysis of a population's gene pool often difficult or impossible? a) Genes are too small to see. b) Conclusions must be inferential, based on phenotypes of reproducing individuals. c) Gene pools are constantly changing too rapidly. d) Only mathematical models can describe them accurately. **Answer: b) Conclusions must be inferential, based on phenotypes of reproducing individuals.** 77. What is the primary difference between **inbreeding** and **outbreeding**? a) Inbreeding increases variation, outbreeding decreases it. b) Inbreeding is mating between relatives, outbreeding is mating between unrelated individuals. c) Inbreeding leads to heterosis, outbreeding leads to depression. d) Inbreeding is always beneficial, outbreeding is always harmful. **Answer: b) Inbreeding is mating between relatives, outbreeding is mating between unrelated individuals.** 78. The Hardy-Weinberg Law deals with the simplest genetic case of a single locus carrying how many alleles? a) One b) Two c) Three d) Many **Answer: b) Two** 79. What is the meaning of "**genetic equilibrium**" in the context of the Hardy-Weinberg Law? a) Allele frequencies are constantly changing. b) Allele and genotype frequencies remain constant. c) Only genotype frequencies change. d) Only allele frequencies change. **Answer: b) Allele and genotype frequencies remain constant.** 80. Which of the following statements about **polymorphism** is true? a) It is always maintained environmentally. b) It excludes continuous variation. c) It refers to rare recessive conditions. d) It cannot be maintained by selection. **Answer: b) It excludes continuous variation.** 81. What is the consequence of non-random mating like assortative mating or consanguinity on the frequency of affected homozygotes? a) It decreases their frequency. b) It increases their frequency. c) It has no effect. d) It only affects heterozygotes. **Answer: b) It increases their frequency.** 82. Which force of evolution is described as the movement of alleles between populations? a) Mutation b) Selection c) Genetic drift d) Gene flow **Answer: d) Gene flow** 83. What is the characteristic description of a population considered under the **Hardy-Weinberg law**? a) It changes genetically and evolves. b) It is an ideal population that does not change genetically. c) It is a small population with high mutation rates. d) It is a population experiencing strong selection pressure. **Answer: b) It is an ideal population that does not change genetically.** 84. According to the text, what are the more important mechanisms maintaining genetic isolation of populations in modern times? a) Geographical barriers b) Cultural rather than geographical barriers c) Natural selection d) High mutation rates **Answer: b) Cultural rather than geographical barriers** 85. What is the effect of **mutation** on allele frequencies? a) It stabilizes allele frequencies. b) It continually introduces new alleles into populations. c) It always decreases allele frequencies. d) It only affects genotype frequencies. **Answer: b) It continually introduces new alleles into populations.** 86. The concept of "**effective population**" is differentiated from "**breeding population**" in that the latter refers to: a) The theoretical ideal population. b) The actual progenitors in a population. c) A population with equal sexes and fertility. d) A population free from evolutionary forces. **Answer: b) The actual progenitors in a population.** 87. Which of the following correctly describes the relationship between '**consanguinity**' and '**inbreeding**'? a) They are interchangeable terms. b) Consanguinity refers to marriage type, inbreeding refers to the mating pattern within a population. c) Inbreeding refers to marriage type, consanguinity refers to mating pattern. d) Consanguinity is a cause of heterosis, inbreeding is a cause of depression. **Answer: b) Consanguinity refers to marriage type, inbreeding refers to the mating pattern within a population.** 88. The Hardy-Weinberg formula is considered a cornerstone of population genetics because: a) It describes how populations evolve rapidly. b) It mathematically describes the behavior of genetic traits through time within a specific unit. c) It predicts the exact number of mutations in a population. d) It explains how migration always leads to equilibrium. **Answer: b) It mathematically describes the behavior of genetic traits through time within a specific unit.** 89. What is the definition of a "**population isolate**"? a) Any population living on an island. b) A group of persons within which individuals choose their partners, often due to geographical or cultural barriers. c) A population that has no genetic variation. d) A population that experiences high rates of gene flow. **Answer: b) A group of persons within which individuals choose their partners, often due to geographical or cultural barriers.** 90. What is the primary effect of **genetic drift** on allele frequencies in **small** populations? a) It stabilizes them. b) It causes random, marked changes. c) It always leads to the loss of all alleles. d) It only affects dominant alleles. **Answer: b) It causes random, marked changes.** 91. If an allele is lost altogether from a population due to genetic drift, it is said to be: a) Fixed b) Mutated c) Extinguished d) Selected **Answer: c) Extinguished** 92. What is the effect of selection against heterozygotes, as seen in cases like maternal-foetal incompatibility (e.g., Rh disease)? a) It increases heterozygote frequency. b) It disturbs Hardy-Weinberg equilibrium. c) It promotes balanced polymorphism. d) It leads to random mating. **Answer: b) It disturbs Hardy-Weinberg equilibrium.** 93. The burden of genetic ill-health and abnormality in human populations can be significantly influenced by: a) Cultural practices alone b) Geographical location alone c) Genetic hazards of radiation d) Dietary habits alone **Answer: c) Genetic hazards of radiation** 94. Which of the following is a characteristic of "**continuous variation**" that differentiates it from polymorphism? a) It is controlled by a single gene. b) It is brought about by the cumulative effect of segregation at many loci and environmental factors (multifactorial). c) It is maintained by balancing selection. d) It applies only to rare conditions. **Answer: b) It is brought about by the cumulative effect of segregation at many loci and environmental factors (multifactorial).** 95. In the context of population genetics, what does "**fitness**" primarily refer to? a) Physical strength of an individual. b) The ability of an individual to survive and reproduce, contributing genes to the next generation. c) The genetic load of a population. d) The rate of mutation. **Answer: b) The ability of an individual to survive and reproduce, contributing genes to the next generation.** 96. If the allele frequency of 'p' is 0.8, what is the frequency of heterozygotes ($2pq$)? a) 0.16 b) 0.32 c) 0.64 d) 0.04 **Answer: b) 0.32 (If $p=0.8$, then $q=0.2$. So $2pq = 2 \times 0.8 \times 0.2 = 0.32$)** 97. Which type of selection leads to the maintenance of multiple alleles in a population? a) Directional selection b) Stabilizing selection c) Disruptive selection d) Balancing selection (e.g., heterozygote advantage) **Answer: d) Balancing selection (e.g., heterozygote advantage)** 98. The term "**breeding isolate**" is synonymous with: a) A large, randomly mating population. b) A population that is geographically separated but exchanges genes. c) A Mendelian population where individuals choose partners within the group. d) A population undergoing rapid gene flow. **Answer: c) A Mendelian population where individuals choose partners within the group.** 99. What is the expected effect of **outbreeding** on a population? a) Increase in homozygosity. b) Decrease in genetic diversity. c) Increase in heterozygosity and potentially reduced expression of recessive disorders. d) Always leads to inbreeding depression. **Answer: c) Increase in heterozygosity and potentially reduced expression of recessive disorders.** 100. If a population is NOT in Hardy-Weinberg equilibrium, it implies that: a) The population is ideal. b) Evolution is occurring. c) There is no genetic variation. d) All individuals have equal fitness. **Answer: b) Evolution is occurring.**