Mendelism, Linkage and Crossing Over (Multiple Choice Questions and Answers))

Mendelism, Linkage and Crossing Over

Multiple Choice Questions and Answers

1. Mendelian combinations are due to

(a) independent assortment of genes

(b) linkage of genes

(c) mutation

(d) dominance

Answer: (a) independent assortment of genes

2. Blue colour in human is recessive to brown eye colour. The expected children of a marriage between a blue eyed woman and a brown eyed man who had blue eyed mother, would be

(a) all blue eyed

(b) all brown eyed

(c) one blue eyed and one brown eyed

(d) all black eyes

Answer: (c) one blue eyed and one brown eyed

3. Sexually reproducing organisms contribute to their offsprings

(a) half of their genes

(b) all the genes

(c) one fourth of their genes

(d) double the number of genes

Answer: (a) half of their genes

4. An individual with two identical members of a pair of genetic factors is called

(a) heteromorphic

(b) heterozygote

(c) homomorphic

(d) homozygote

Answer: (d) homozygote

5. A plant is heterozygous and is designated Bb, it produces two kinds of the gametes B and b. The probability of b gamete fertilizing B or b is

(a) 1/2

(b) 1/1

(c) 0/1

(d) 1/4

Answer: (b) 1/1

6. The plants are considered to be true breeding when

(a) all the plants of the parental generation resemble each other

(b) the progeny occupies less space

(c) the progeny may show genetic variability which may finally be utilised for evolving a better type

(d) the progeny is free of disease

Answer: (a) all the plants of the parental generation resemble each other

 7. Using two pairs-tall and dwarf and smooth and wrinkled seeds the principle of independent assortment of characters is proved by the

(a) observation that F1 progeny is tall

(b) appearance of tall and dwarf in 3:1 ratio and also the appearance of smooth and wrinkled seeded plants in 3:1 ratio in F2 population

(c) appearance of tall and dwarf plants in F2 population

(d) appearance of smooth and wrinkled seeded plants, F2 population

Answer: (b) appearance of tall and dwarf in 3:1 ratio and also the appearance of smooth and wrinkled seeded plants in 3:1 ratio in F2 population

 8. The percentage of ab gametes produced by AaBb parent will be

(a) 12.5

(b) 25

(c) 50

(d) 75

Answer: (b) 25

 9. Dominant gene for tallness is T and for yellow colour is Y. If a plant heterozygous for both the traits is selfed, then the ratio of pure homozygous dwarf and green offsprings would be

(a) 1/4

(b) 4/16

(c) 3/16

(d) 1/16

Answer: (d) 1/16

 10. How many pairs of contrasting characters in pea pod were chosen by Mendel?

(a) 2

(b) 3

(c) 4

(d) 7

Answer: (a) 2

 11.  A cross between F1 hybrid and a recessive parent gives the ratio of

(a) 3:1

(b) 1:1

(c) 2:1

(d) 4:1

Answer: (b) 1:1

 12. If a homozygous tall male plant (dominant) is crossed with a homozygous dwarf male plant (recessive), genotype of endosperm would be

(a) ttt

(b) ttT

(c) TTt

(d) TTT

Answer: (c) TTt

 13. How many types of genetically different gametes would be produced by a heterozygous plant having the genotype AABbCc

(a) 2

(b) 4

(c) 6

(d) 9

Answer: (b) 4

 14. The genes controlling 7 traits in pea studied by Mendel were later found to be located on how many chromosomes?

(a) 7

(b) 4

(c) 5

(d) 6

Answer: (b) 4

 15. In a monohybrid cross red colour of flower (RR) is dominant over white colour of flower (rr). What will be the phenotypic ratio of the offsprings from a cross between Rr x rr parents?

(a) 50% red and 50% white

(b) 75% red and 25% white

(c) 100% red

(d) 100% white

Answer: (a) 50% red and 50% white

 16. If a dwarf plant was treated with gibberellic acid, it grew as tall as the pure tall plant. If this treated plant is crossed with pure tall plant, then the phenotypic ratio of F1 generation is likely to be

(a) 50% dwarf and 50% tall

(b) 75% tall and dwarf 25%

(c) all dwarf

(d) all tall

Answer: (d) all tall

17. The universally applicable law of Mendel is

(a) law of dominance

(b) law of unit characters

(c) law of segregation

(d) law of independent assortment

Answer: (c) law of segregation

18. Genotypic and phenotypic ratios are same in

(a) a cross involving sex linked traits

(b) a test cross

(c) monohybrid cross in which homozygous dominant alleles become lethal

(d) none of these

Answer: (b) a test cross

19. In pea plants, yellow pea is dominant over green pea. Give the genotype of all plants that could possibly produce green peas when crossed with a heterozygote.

(a) YY and yy

(b) yy and YY

(c) Yy and Yy

(d) Yy

Answer: (c) Yy and Yy

 20. In a dihybrid cross what percentage of F1 progeny are obtained for both the traits?

(a) 8%

(b) 12.5%

(c) 25%

(d) 50%

Answer: (b) 12.5%

 21. When a heterozygous dominant is crossed with homozygous recessive, then the ratio in the next filial generation will be

(a) 1:2

(b) 2:1

(c) 3:1

(d) 1:1

Answer: (d) 1:1

 22. Probability of four sons to a couple is

(a) 1/4

(b) 1/8

(c) 1/16

(d) 1/32

Answer: (c) 1/16

 23. A gamete normally contains

(a) two alleles of a gene

(b) one allele of a gene

(c) many alleles of a gene

(d) all alleles of a gene

Answer: (b) one allele of a gene

 24. Two crosses between the same pair of genotypes or phenotypes in which the sources of the gametes are reversed in one cross, is known as

(a) test cross

(b) reciprocal cross

(c) dihybrid cross

(d) reverse cross

Answer: (b) reciprocal cross

 25. In codominance F1 hybrids show

(a) both dominant and recessive characters

(b) only dominant character

(c) only recessive character

(d) intermediate character between dominant and recessive

Answer: (a) both dominant and recessive characters

 26. In case of incomplete dominance in F2 generation

(a) genotypic ratio 3:1

(b) phenotypic ratio is 3:1

(c) genotype ratio is equal to phenotypic ratio

(d) nothing can be concluded

Answer: (b) phenotypic ratio is 3:1

 27. Which of the following statements about crossing-over is most correct?

(a) There are as many crossings over possibilities as there are genes on the chromosome.

(b) The farther apart are the two genes on chromosome, greater are the chances of their crossing over.

(c) Genes placed linearly adjacent on a chromosome have the greatest chances of crossing over

(d) crossing over does not occur at a distance of more than 5 map units

Answer: (b) The farther apart are the two genes on chromosome, greater are the chances of their crossing over.

 28. Linkage was discovered by

(a) Blakeslee

(b) Sutton

(c) Muller

(d) Bateson

Answer: (d) Bateson

 29. Often two genes do not assort independently as predicted by Mendel’s principle of independent assortment. However, even in such linked genes, linked it is never complete because of

(a) crossing over

(b) the phenomenon of dominance

(c) inversions

(d) certain enzymes which cleave DNA between two genes

Answer: (a) crossing over

30. Crossing over in diploid organism is responsible for

(a) Recombination of linked genes

(b) Segregation of alleles

(c) Dominance of genes

(d) Linkage between genes

Answer: (b) Segregation of alleles

 31. A pair of genes may be called linked only if their recombination frequency in a test cross is

(a) higher than the expected value of 50%

(b) lower than the expected value of 50%

(c) equal to the expected value

(d) none of the above

Answer: (a) higher than the expected value of 50%

 32. What will be the number of linkage groups in maize if it has 10 pairs of chromosomes?

(a) 5

(b) 10

(c) 20

(d) 30

Answer: (b) 10

33. A and B genes are linked. What shall be the genotype of progeny in a cross between ABab and aabb?

(a) AAbb and aabb

(b) AaBb and aabb

(c) AABB and aabb

(d) None

Answer: (c) AABB and aabb

34. When a cluster of genes show linkage behaviour they

(a) do not show a chromosome map

(b) show recombination during meiosis

(c) do not show independent assortment

(d) induce cell division

Answer: (c) do not show independent assortment

 35. Crossing over that result in genetic recombination in higher organisms occurs between

(a) two different bivalents

(b) sister chromatids of a bivalent

(c) non sister chromatids of a bivalent

(d) two daughter nuclei

Answer: (c) non sister chromatids of a bivalent

 36. Lack of independent assortment of two genes A and B in fruit fly Drosophila is due to

(a) crossing over

(b) repulsion

(c) recombination

(d) linkage

Answer: (d) linkage

 37. Substitution of a purine nucleotide by pyrimidine nucleotide is known as

(a) transition

(b) transversion

(c) inversion

(d) transduction

Answer: (b) transversion

 38. Trisomy has a chromosome complement of

(a) 2n-1

(b) 2n+3

(c) 2n+2

(d) 2n+1

Answer: (d) 2n+1

39. Which of the following is a base analogue?

(a) 5-bromouracil

(b) caffeine

(c) colchicine

(d) nitrous acid

Answer: (a) 5-bromouracil

 40. A complete set of chromosomes inherited as a unit from one parent is called

(a) Genome

(b) Genotype

(c) Nucleoid

(d) Euploid

Answer: (a) Genome

 41. The plant which made Hugo De vries famous is

(a) Antirrhinum majus

(b) Lathyrus odoratus

(c) Oenothera lamarckiana

(d) Pisum sativum

Answer: (c) Oenothera lamarckiana

 42. Raphanobrassica is an example of

(a) trisomic

(b) allopolyploid

(c) autopolyploid

(d) amphidiploids

Answer: (b) allopolyploid

 43. Datura is a classic example of

(a) euploidy

(b) monosomy

(c) trisomy

(d) inversion

Answer: (c) trisomy

 44. Insertion or deletion of a single base causes

(a) inversion mutation

(b) transition mutation

(c) frame-shift mutation

(d) transversion mutation

Answer: (c) frame-shift mutation

 45. The number of phenotypes in ABO blood group is

(a) 1

(b) 4

(c) 6

(d) 8

Answer: (b) 4

 46. Mutations can be induced with

(a) ethylene

(b) gamma radiations

(c) infrared radiations

(d) IAA

Answer: (b) gamma radiations

 47. Base substitution caused by base analogues is

(a) transition

(b) transversion

(c) complementation

(d) translocation

Answer: (a) transition

 48. Cancer cells are most easily damaged by radiations than normal cells because they are

(a) non dividing

(b) starved of mutation

(c) undergoing rapid division

(d) different in structure

Answer: (c) undergoing rapid division

 49. A nutritionally wild type of organism, which does not require any additional growth supplement is known as

(a) prototroph

(b) phenotroph

(c) holotype

(d) auxotroph

Answer: (d) auxotroph

 50. What base is responsible for hot spots for spontaneous point mutations?

(a) 5-bromouracil

(b) 5-methyl cytosine

(c) adenine

(d) guanine

Answer: (d) guanine