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Friday, 1 April 2016

FSc Notes Biology Part 2 Chapter 22 Variation and Genetics Short Questions

FSc Notes Biology Part 2 Chapter 22 Variation and Genetics Short Questions


Q 1. What is the difference between phenotype and genotype?
Ans. Phenotype is the form of appearance of a trait. Genotype is the genetic complement i.e., the genes in an individual for a particular trait.

Q 2. Define population?
Ans. Any group of sexually interbreeding organisms of the same species that exist together in both time and space is called population.

Q 3. What is the product rule?
Ans. When two independent events are occurring simultaneously like in /dihybird cross, the ratio of each joint phenotype combination can be obtained by multiplying the probabilities of individual phenotypes. It is called product rule.

Q 4. Name difference types of dominance relations among alleles?
Ans. There are four types of dominance relations among alleles, each indicating a different style of their functional effects upon each other.
     1. Complete dominance.    2. Incomplete dominance.
     3. Condominance.             4. Over dominance.

Q 5. Who discovered ABO blood group?
Ans. Karl Landsteiner discovered ABO group system in 1901.

Q 6. What epistasis?
Ans. When an effect caused by a gene or gene pair at one locus interferes with or hides the effect caused by another gene or gene pair at another locus, such a phenomenon of gene interaction is called epistasis.

Q 7. What are polygenetic traits?
Ans. A continuously varying trait is encoded by alleles of two or more different gene pairs found at different loci, all influencing the same trait in an additive way. These quantitative traits are called polygenetic traits, and their genes or polygenes.

Q 8. What is Cross over or recombinant frequency?
Ans. It is the proportion of recombinant types between two genes pairs as compared to the sum of all combinations.

                      Recombinant Frequency = Recombinant types / Sum of all combinations * 100

Q 9. Name the organism that lack sex chromosomes?
Ans. Many species of eukaryotic microorganisms like yeast do not have sex chromosome.

Q 10. Which one is true colour blindess: monochromacy or dichromacy?
Ans. Monochromacy is true colour blindess.

Q 11. How and why did Mendelian factors behave like chromosomes?
Ans. Mendelian factors behave like chromosomes because these factors (now called genes) are located on the chromosomes or in other words they are the part of chromosomes.

Q 12. How sexual dimorphism is exhibited in Drosophila?
Ans. Male and female Drosophila shows sexual dimorphism i.e., these are morphologically distinct from each other. Male is smaller in size with black rounded abdomen. Female is larger with pointed abdomen. Male has sex combs on front legs.

Q 13. Differentiate between Gene and genome?
Ans. Gene is the basic unit of biological information. Hereditary characteristics pass from parents to offspring through genes in their gametes. The genetic materials of an organism is the genome.

Q 14. What are genes and alleles?
Ans. Gene is the basic unit of biological information. Genes are actually parts of DNA comprising its base sequences. An allele is a member of the gene pair.

Q 15. Differentiate between Monohybrid and dihybrid?
Ans. A hybrid for a single trait under consideration is said to be monohybrid while a hybrid for two traits under consideration is called dihybrid.

Q 16. Differentiate between Homozygous and heterozygous?
Ans. When both the alleles of a gene pair in an organism are some, the organism is homozygous for that gene pair e.g., 'RR' or 'rr' When the two alleles of a gene pair in an organism are different, the organism is heterozygous for that gene pair e.g., 'Rr'.

Q 17. Differentiate between Dominance and epistasis?
Ans. Dominance is a physiological effect of an allele over its partner allele on the same gene locus.
When an effect caused by a gene or gene pair at one locus interferes with or hides the effect caused by another gene or gene pair at another locus, such a phenomenon of gene interaction is called epistasis.

Q 18. Differentiate between Autosome and sex chromosome?
Ans. All chromosomes other than sex-chromosomes are called autosomes. X and Y chromosomes are called sex-chromosomes because these have genes for determination of sex.

Q 19. Differentiate between Allele and multiple allele?
Ans. Partners of a gene pair are called alleles. Each allele of a gene pair occupies the same gene locus on its respective homologous i.e., RR or Rr etc.

Q 20. Differentiate between Sex limited and sex influenced trait?
Ans. A sex-limited trait is limited to only one sex sue to anatomical differences e.g., beard growth in humans is limited to men. Sex influenced trait occurs in both males and females but it is more common in one sex. Pattern baldness is a sex influenced trait that is more common in men.

Q 21. Differentiate between Incomplete dominance and codominance?
Ans. "When the phenotype of the heterozygote is intermediate between phenotypes of the two homozygotes, it is called incomplete or partial dominance e.g., 4 O'clock pink flower.
Different alleles of a gene that are both expressed in a heterozygous condition are called codominant and the phenomenon is called codominance e.g., MN blood type.

Q 22. Differentiate between Dominant and recessive trait?
Ans. A trait that appears in a hybrid between two true breeding varieties is called dominant trait while a trait that is suppressed or masked in a hybrid between two true breeding varieties, it is said to be recessive.

Q 23. Differentiate between Continuous and discontinuous variations?
Ans. Some traits show more than two qualitatively different phenotypes, this is called continuous variations e.g., wheat grain colors, human height; skin colour and intelligence. There are many traits which have only two sharply defined phenotype, this is called discontinuous variation e.g., height, colour, shape in pea plant as studied by Mendel.

Q 24. Differentiate between Wild type and mutant?
Ans. An organism with normally existing traits (present in majority of the individuals of the population) is called wild type while an organism with a trait developed due to mutation is said to be mutant.

Q 25. What is a gene pool?
Ans. All the genes / alleles found in a breeding population at a given time are collectively called the gene pool. It is the total genetic information encoded in the total genes in a breeding population existing at given time.

Q 26. What  pea a lucky choice for Mendel? What would have happened if he had studied an eight character?
Ans. Yes, pea was a lucky choice for Mendel as he studied seven traits and pea plant has seven pairs of chromosomes. The genes of these traits were luckily located on separate chromosomes so he found independent assortment. If he had studied the eight character, he might encountered with deviation from independent assortment.

Q 27. What is a test cross? Why did Mednel devise this cross?
Ans. Test cross is a mating in which an individual showing a dominant phenotype is crossed with an individual showing its recessive phenotype. This cross finds out the homozygous or heterozygous nature of the genotype. Mendel devised a cross to test the genotype of an individual showing a dominant phenotype.

Q 28. What would happen if alleles of a pair do not segregate at meiosis? How would it affect the purity of gamete?
Ans. If alleles of a pair do not segregate at meiosis, some gametes have an extra chromosome while others would lack one chromosome. This process is called non-disjunction. This phenomenon disturbs the purity of gametes according to which each gamete should received only one of the two alleles.

Q 29. If the alleles do not assort independently, which type of combination is missing in the progency?
Ans. The recombination would be missing in the progency.

Q 30. Why each gamete had equal chance of getting one or the other allele of a pair?
Ans. It is because of meiosis and segregation.

Q 31. Does the dominant allele modify the determinative nature of its recessive partner? What sort of relationship do they have?
Ans. The dominant allele does not modify the determinative nature of its recessive partner. Dominance is a physiological effect of an allele over its partner allele on the same locus. When one allele is completely dominant over the other, presence of recessive allele is functionally hidden. So the heterozygote has the same phenotype as homozygote.

Q 32. Which type of traits can assort independently?
Ans. The traits located on different chromosomes can assort independently.

Q 33. Why does the blood group phenotype of a person remain constant through out life?
Ans. The blood group phenotype is controlled by genes which will never change or mutate during the life time of a person so blood group phenotype remains throughout the life.

Q 34. What is a universal blood donor?
Ans. O blood group individuals are called universal donors. Phenotype O can also be sued as donor for small transfusions to A, B and AB recipients because donor's antibodies are quickly absorbed by other tissues or greatly diluted in the recipient's blood stream.

Q 35. How can ABO - incompatibility protect the baby against Rh - incompatibility?
Ans. Sometimes a mild ABO incompatibility protects the baby against more severe Rh incompatibility. If O' mother conceives A' or B' baby, any foetal A or B type RBC entering the mother's blood are quickly destroyed by her anti - A or anti - B antibodies, before she can form anti - Rh antibodies.

Q 36. Which types of genes do not obey law of independent assortment?
Ans. The genes located on the same chromosome do not obey law of independent.

Q 37. How can linked genes be separated from each other?
Ans. The linked genes can be separated from each other by crossing over.

Q 38. What is multifactorial inheritance?
Ans. The inheritance of trait which is controlled by several genes and is affected by environmental factors as well as is called multifactorial (polygenic with environmental influence) inheritance.

Q 39. What is MODY?
Ans. About 2% - 5% of type II diabetes get the disease early in life, before 25 years of age. It is called maturity onset diabetes of the young (MODY). MODY can be inherited as an autosomal dominant trait. About 50% of cases of MODY are caused by mutations in glucokinase gene.

Q 40. Can a child have more intelligence (IQ score) than his parents?
Ans. Yes, a child may have more intelligence (IQ score) than his parents.

Q 41. What is Locus?
Ans. The position of a gene on the chromosome is called its locus.

Q 42. What are Alleles?
Ans. Partners of a gene pair are called alleles. Each allele of a gene pair occupies the same gene locus on its respective homolgue. Both alleles on one locus may be identical, or different from each other.

Q 43. Why Mendel is famous for?
Ans. Gregor Johann Mendel laid the foundation of classical genetics by formulating two laws of heredity; law of segregation and law of independent assortment.

Q 44. Define Mendel's law of segregation (law of purity of gamete)?
Ans. According to law of segregation, the two coexisting alleles for each trait in an individual segregate (separate) from each other, so that each gamete receives only one of the two alleles.

Q 45. What is Punnett square?
Ans. Punnett square is a checker box in which male gametes are put on one side and female gametes on the other side and their combined results are placed in corresponding boxes to get the genotypic and phenotypic ratios of the next generations.

Q 46. Define Mendel's Law of independent Assortment or simultaneous inheritance of two traits?
Ans. Mendel formulated Law of Independent Assortment: "When two contrasting pairs of traits are followed in the same cross, their alleles assort independently into gametes."

Q 47. What is Linkage group?
Ans. All the genes present on a homologous pair of chromosome are linked to each other in the form of linkage group. These cannot assort independently.

Q 48. What is Over dominance?
Ans. In this case the over dominant heterozygote exceeds in quantity the phenotypic expression of both the homozygotes.

Q 49. Who discovered ABO blood group?
Ans. ABO blood group system (the first multiple allelic system) was discovered by Karl Landsteiner in 1901.

Q 50. Why Berstein is famous for?
Ans. Berstein explained the genetic basis of ABO system in 1925.

Q 51. What is antigen is produced by allele IA, IB and i?
Ans. Allele IA specifies production of antigen A, and allele IB specifies production of antigen B, but allele i does not specify any antigen.

Q 52. What phenotypes would be produced by the following genotypes: IAIA, IAi, IBi and ii in ABO blood system?
Ans. IAIA or IAi genotypes will produced phenotype A. Similarly IBIB or IBi produces phenotype B. The homozygoous ii will produce phenotype O.

Q 53. Why blood group phenotype never changes?
Ans. The blood group alleles start their expression at early embryonic stage and keep on expressing themselves till death. Therefore the blood group phenotype of a persons never changes throughout life.

Q 54. Name the anti-bodies found in blood serum of phenotype A, B AB and O?
Ans. The blood serum of a phenotype contains anti-B antibodies. B phenotype contains anti-A antibodies. Phenotypes AB has neither anti-A nor anti-B antibodies in the serum. The serum of O blood type contains both anti-A and anti-B antibodies.

Q 55. What is antiserum?
Ans. The blood serum containing antibodies is called antiserum.

Q 56. Why phenotype O is called universal donor?
Ans. Phenotype O can be used as donor for small transfusions to A, B and AB recipients because donor's antibodies are quickly absorbed by other tissues or greatly diluted in the recipient's blood stream. So O blood group individuals are called universal donors.

Q 57. Why AB blood group individuals are called universal recipients?
Ans. AB blood group individuals are called universal recipients because they can received transfusions of blood from any of the four blood groups.

Q 58. What is Rh - Blood group system?
Ans. Rh- blood group system is defined on the basis of Rh-factor present on the surface of RBC. This system is named Rh after Rhesus monkey, because its antigen was first discovered in it by Landsteiner.

Q 59. What is Erythroblastosis foetalis (Meternal - foetal Rh incompatibility)?
Ans. When Rh mother's anti - Rh antibodies seep through placenta into blood circulation of Rh foetus, they start haemolysis (break down / bursting) of RBC of foetus. This condition is called Erythroblastosis foetails. As this destruction continuous, the foetus becomes anaemic.

Q 60. Why erythroblastosis foetalis is called so?
Ans. The anaemic foetus starts to release many immature erythroblasts into his blood stream. That is why this haemolytic disease of the new born is called erythroblastosis foetalis.

Q 61. What is Bombay phenotype?
Ans. They are phenotypically like O, but are not genotypically O. Their RBC lack A and B antigens although they do not lack IA and IB genes.

Q 62. Define pleiotropy?
Ans. When a single gene affects two or more traits, the phenomenon is called pleiotropy. Such a gene with multiple phenotypic effects is called pleiotropic.

Q 63. What does happen when a cat gets W allele?
Ans. Its melanocytes fails to develop properly. melanocyte failure causes both pheontypes, i.e., white fur and deafness.

Q 64. What are two aspects of phenotypic expression of traits?
Ans. Pheonotypic expression of traits has two aspects:
     i) Qualitative.   ii) Quantitative.

Q 65. What environmental factors affect the grain colour in wheat?
Ans. Environmental factors like light, water and nutrients also influence the amount of grain colour.

Q 66. What do you know about the tallness and shortness in humans?
Ans. Tallness in human is recessive to shortness. More the number of dominant alleles for shortness, the shorter the height will be. Similarly greater the number of recessive alleles for tallness, the taller the height will be.

Q 67. What is gene linkage?
Ans. The phenomenon of staying together of all the genes of a chromosome is called linkage.

Q 68. Define crossing over?
Ans. Crossing over is an exchange of segments between non-sister chromatids of homologous chromosomes during meiosis.

Q 69. How many pairs of sex and autosome chromosomes are present in humans?
Ans. 22 pairs of autosomes and one pair of sex-chromosomes are found in humans.

Q 70. What is SRY?
Ans. SRY is the male determining gene. It is located at the tip of short arm of Y-chromosome. Its name SRY stands for "Sex determining regions of Y".

Q 71. What do you know about chromosome number of Grasshopper?
Ans. The female has 24 chromosomes in the form of 11 pairs of autosomes and a pair of X-chromosomes. But the male grasshopper has 23 chromosomes having 11 pairs of autosomes and only one X chromosome. Thus male is XO and female is XX.

Q 72. Differentiate between homogametic and heterogametic individuals?
Ans. If an individual has two similar types of sex chromosomes it is said to be homogentic e.g., human females is XX. Similarly if an individual has two different types of sex chromosomes or only X is present, it is said to be geterogametic e.g., human male is XY or male grasshopper is XO.

Q 73. What is nullo gamete?
Ans. A gametes without any sex chromosome is called nullo gamete. For example in male grasshopper half of the gametes are nullo gametes.

Q 74. Which animals show XX - XY type or WZ - ZZ type of sex determination?
Ans. This type of sex - determination pattern is common in birds, butterflies and moths. It was discovered by J. Seiler in 1914 in moth.

Q 75. Compare XXY individuals in humans and Drosophila?
Ans. XXY individual produced through non disjunctional gametes in humans is a sterile male called Klinefelter's syndrome, but the same XXY set of chromosomes in Drosphila produces a fertile female.

Q 76. What is X:A ratio for females and males?
Ans. An X : A ratio of 1.00 or higher produces females whereas an X : A ratio of 0.5 or lower produces males.

Q 77. Differentiate between monoecious and dioecious plants?
Ans. Most plants have both male and female sex organs on the same plant and are said to be monoecious while some species like Ginkgo are dioecious having plants of separate sexes. Male plants produce flowers with only stamens and female plants produce flowers with only carpels.

Q 78. Why Correns is famous for?
Ans. Correns (1907) discovered the pollen of certain plants were sex-determining.

Q 79. Why T.H. Morgan is famous for?
Ans. Thomas Hunt Morgan (1910) provided experimental in support of chromosomal theory of heredity through discovery of sex linkage in fruit fly Drosophila.

Q 80. Why single recessive allele on X chromosome can express itself in males?
Ans. It is because Y chromosome is empty for that gene. Males are hemizygous as they carry just one allele on their X chromosome.

Q 81. What are Sex-linked and X-linked traits?
Ans. A trait whose gene is present on X chromosome is called X-linked trait. X-linked traits are commonly referred to as sex-linked traits.

Q 82. What is the Pattern of sex-linked inheritance?
Ans. An X - linked trait passes in a crisscross fashion from maternal grandfather (P1) through his daughter (F1) to the grandson (F2). It never passes direct from father to son because a son inherits only Y chromosome from father.

Q 83. What are Y-linked genes?
Ans. Y chromosome does carry a few genes which have no counterpart on X chromosome. Such genes are called Y-linked genes and their traits are called Y-linked traits e.g., SRY gene.

Q 84. What are X - and Y - genes?
Ans. Some genes like bobbed gene in Drosophila are present on X and Y both. These are called X - and Y - linked genes.

Q 85. Why X - and - Y linked genes are called pseudoautosomal?
Ans. It is because their pattern of inheritance is like autosomal genes.

Q 86. What are X - linked dominant and recessive traits?
Ans. Human have many X - linked traits of which some like haemophilia and colour blindness are X - linked recessive traits while others, like hypophosphatemic or vitamin D resistant rickets are X - linked dominant traits.

Q 87. What is haemophilia?
Ans. Haemophilia is a rare X - linked recessive trait. Hemophiliac's blood fails to clot after an injury, because it has either a reduction or malfunction or complete absence of blood clotting factors.

Q 88. What are different types of haemophilia?
Ans. Haemophilia is of three types: A, B and C Haemophilia A and B are non - allelic recessive sex - linked, but haemophilia C is an autosomal recessive trait.

Q 89. What is the percentage of different types of haemophilia?
Ans. 80% hemophiliacs, suffers from haemophilia A due to abnormality of factor VIII, about 20% suffer from haemophilia B due to disturbance in factor, IX, but less than 1% suffer from haemophilia C due to reduction in factor XI.

Q 90. Which type of haemophilia affect men more than women?
Ans. Being X - linked recessives, haemophilia A and B affect men more than women, but haemophilia C affects both the sexes equally because it is autosomal.

Q 91. When a woman can suffer from haemophilia A or B?
Ans. A woman can suffer from haemophilia A or B only when she is homozygous for the recessive allele.

Q 92. What is the pattern of inheritance of haemophilia?
Ans. Haemophilia A and B zigzag from maternal grandfather through a carrier daughter to a grandson. It never passes direct from father to son.

Q 93. What are opsins?
Ans. Each type of cone cell has specific light absorbing proteins called opsins. The genes for red and green opsins are on X chromosome, while the gene for blue opsins is present on autosome 7.

Q 94. What is dichromat? What are different types of dichromatic blindness?
Ans. A dichromat can perceive two primary colours but is unable to perceive the one whose opsins are missing due to mutation?
     i) Protanopia.   ii) Deuteranopia.   iii) Tritanopia.

Q 95. Differentiate between protanopia deuteranopia and tritanopia?
Ans. i) Protanopia is red colour blindness.
    ii) Deuteranopia is green colour blindness.
   iii) Tritanopia is blue colour blindness.

Q 96. What are protanomalous and deuteranomalous?
Ans. Some people can detect red and green but with altered perception of the relative shades of these colours (i.e., they can see red instead of green and vice versa). They have abnormal but still partially functional opsins. They are protanomalous and deuteranomalous respectively.

Q 97. What is Monochromacy?
Ans. A monochromat can perceive only one colour. Monochromacy is true colour blindness.

Q 98. What is Blue cone monochromacy?
Ans. Blue cone monochromacy is an X - linked recessive trait in which both red and green cone cells are absent. That is why it is also called red - green colours blindness.

Q 99. Why red-green colour blindness is more common in men than women?
Ans. It is because chances for a male to be affected by it are double than a female as Y chromosome has no alternate gene.

Q 100. What is the pattern of X - linked dominant inheritance?
Ans. It is more common in females than males. all daughters of an affected father are affected, but none of his sons are affected. Any heterozygous affected mother will pass the trait equally to half of her sons and half of her daughters. hypophosphatemic rickets is an X - linked dominant trait.

Q 101. What is the pattern of Y - Linked inheritance?
Ans. Y - linked trait passes through Y - chromosome from father to son only. Such traits cannot pass to daughters because they do not inherit Y - chromosome. All sons of an affected father are affected by a Y - linked traits. 'SRY' gene on Y chromosome determines maleness in man.

Q 102. What are sex limited traits?
Ans. A sex-limited trait is limited to only one sex due to anatomical difference. Such traits affects a structure or function of the body present in only males or only females. These traits may be controlled by sex-linked or autosomal genes.

Q 103. What are sex-influenced traits?
Ans. Sex influenced trait occurs in both males and females but it is more common in one sex. It is controlled by an allele that is expressed as dominant in one sex but recessive in the other. This difference in expression is due to hormonal difference e.g., Pattern baldness.

Q 104. A man is 45 years old and bald. His wife also has pattern baldness. What is the risk that their son will lose his hair?
Ans. The son has 100% chance to lose hair.

Q 105. what is Diabetes mellitus?
Ans. Diabetes mellitus is a hereditary disease, characterized by high blood sugar level. Diabetics pass glucose in their urine.

Q 106. What are effected of diabetes?
Ans. Diabetes is the leading cause of kidney failure, adult blindness, lower limb amputation and heart disease.

Q 107. What is Type I diabetes or IDDM or insulin dependent diabetes mellitus?
Ans. Type I diabetes is also called Juvenile diabetes because it usually occurs in early age before 40. It arises due to deficiency of pancreatic hormone insulin that normally routes blood glucose to cells for use. Diabetics of type I must receive oxygenous (from outside source) insulin to survive.

Q 108. What is Type II diabetes or NIDDM or non insulin dependent diabetes mellitus?
Ans. Diabetes mellitus type II accounts for 90% of all diabetic patients. These persons produced some endogenous insulin themselves, but their body cells gradually fail to respond to insulin and cannot take up glucose from blood. It occurs among people over age 40. and is more common among the obese (very fat).

Written by: Usman Rashid & Asad Hussain

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