Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that
1. new mutations were frequently generated in the F2 progeny, "reinventing" traits that had been lost in the F1.
2. the mechanism controlling the appearance of traits was different between the F1 and the F2 plants.
3. traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.
4. the traits were lost in the F1 due to dominance of the parental traits.

Subtopic:  Monohybrid Cross: 1 | Monohybrid Cross: Further Understanding |
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In the following questions a statement of assertion (A) is followed by a statement of reason (R).
Assertion (A): Organisms lacking one complete chromosome are called monosomics.
Reason (R): Down’s syndrome is an example of monosomy.
  
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. Both (A) and (R) are false.
  1. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
  2. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
  3. If the assertion is true but the reason is false
  4. If both the assertion and reason are false
Subtopic:  Non - Disjunction & Aneuploidy | Sex Aneuploidy - Turner & Klinefelter Syndrome |
 70%
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Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?
1. incomplete dominance
2. multiple alleles

3.  pleiotropy
4. epistasis

 
Subtopic:  Polygenic Inheritance & Pleiotropy | Mendelian Disorders |
 75%
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How would one explain a test cross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced?
1. The two genes are closely linked on the same chromosome
2. The two genes are linked but on different chromosomes
3. Recombination did not occur in the cell during meiosis
4. The test cross was improperly performed
Subtopic:  Understanding Linkage | Linkage Types | Recombination & Gene Mapping |
 84%
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In a linear chromosome map distances between four loci are -a and b = 20 mu; a and d = 6mu; b and c=8 mu; a and c= 12 mu. What will be the crossover frequency between c and d ? 
1. 12% 
2. 20% 
3. 3% 
4. 6%
Subtopic:  Chromosomal Basis of Inheritance: Introduction | Linkage Types | Recombination & Gene Mapping |
 58%
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Which of the following display female heterogametry? 
1. Drosophila melanogaster 
2. Apis mellifera 
3. Gallus gallus domesticus 
4. Periplaneta Americana 
Subtopic:  Sex Determination | Sex Determination: Further Considerations |
 56%
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In a particular chromosome, the recombination frequency between genes a &c is 5%; b & c is 15%; b &d is 9%; a &b is 20%; c &d is 24% and a & d is 29%. The sequence of genes in a chromosome is 
1. a, d, b, c 
2. d, b, a, c 
3. a, b, c, d 
4. a, c, b, d 
Subtopic:  Chromosomal Basis of Inheritance: Introduction | Recombination & Gene Mapping |
 69%
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Which one of the following anticodons are used for the translation of t-RNA during the biosynthesis of hemoglobin in sickel cell anemic patients? 
1. CAC 
2. CUC 
3. GUG 
4. GAG 
Subtopic:  Mendelian Disorders: Sickle Cell Anemia |
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Match List I with List II
                       
List I     List II
A. Mendelian Disorder  I. Chromosomal Theory of inheritance
B. Alfred Sturtevant II. Klinefelter's syndrome
C. Chromosomal Disorder III. Cystic fibrosis
D. Sutton and Boveri IV. Used the frequency of recombination between the gene pair in the same chromosome

Choose the correct answer from the options given below:
1. A-III   B-I      C-II     D-IV
2. A-III   B- IV   C-II     D-I
3. A-IV   B-III    C-II     D-I
4. A-II     B-III   C-I      D-IV
 
Subtopic:  Chromosomal Basis of Inheritance: Introduction | Chromosomal Basis of Inheritance: Further Considerations | Recombination & Gene Mapping | Mendelian Disorders |
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If two plants having heterozygous genotype for a trait are crossed, what percentage of the progeny will have heterozygous genotype?
1.  25%
2.  50%
3.  75%
4.  100%
Subtopic:  Monohybrid Cross: 1 | Monohybrid Cross: Further Understanding |
 86%
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