Bridges' Experiment on Nondisjunction in Drosophila

Q. When Morgan chose body colour and eye colour to be the characters for dihybrid crosses in Drosophila, he obtained a greater percentage of parental traits in the progeny. Which of the following inferences can be drawn from the above observation?

1. The progeny were a result of asexual reproduction, hence were identical to the parents.
2. The genes for these characters were inherited as a single unit.
3. The genes for these characters were located far apart on the same chromosome.
4. The genes were located on autosomes.

Q. A scientist conducted a crossing experiment with Drosophila. From the experimental results he concluded that crossing over occurs in females but not in males. From this information, choose the correct statement regarding the types of gametes produced by the female and the male flies. The male and female both have the same genotype (AB/ab).

1. 4 types of gametes in females and 2 types in males
2. 2 types of gametes in both females and males
3. 2 types of gametes in females and 4 types in males
4. 4 types of gametes in both females and males

Q. When red eyed males are crossed with white eyed females, one expects white eyed males and red eyed females in F₁ generation. However, Bridges found that sometimes, in such a cross, red eyed males and white eyed females could be observed. What was the reason for this observation?

1. Epistasis
2. Non-disjunction of X chromosomes
3. Codominance
4. Homologous recombination

Q.

Mr. Joseph crosses a heterozygous red eyed female Drosophila with a white eyed male. What will be the characters of males and females after $F_1$ generation respectively?

1. white eyed females and red eyed males
2. 50% red and 50% white eyed female as well as males
3. 50% red and 50% white eyed females and 100% white eyed males
4. red eyed females and white eyed males

Q. When red eyed males are crossed with white eyed females, one expects white eyed males and red eyed females in F₁ generation. However, Bridges found that sometimes, in such a cross, red eyed males and white eyed females could be observed. What was the reason for this observation?

1. Non-disjunction of X chromosomes
2. Epistasis
3. Codominance
4. Homologous recombination

Q. In fruit fly genes for red, eosin and white eye colour are allelic and sex linked. Gene for yellow body is linked with white eye with a cross over value of 1.5%. The probable crossover value between eosin and yellow body allele would be then

1. 1.5%
2. 3%
3. data insufficient
4. 0.75%

Q.

Mr. Joseph crosses a heterozygous red eyed female Drosophila with a white eyed male. What will be the characters of males and females after $F_1$ generation respectively?

1. red eyed females and white eyed males
2. 50% red and 50% white eyed female as well as males
3. white eyed females and red eyed males
4. 50% red and 50% white eyed females and 100% white eyed males

Q. In which type of inheritance the results are affected by reciprocal cross?

1. All of the above
2. Blending
3. Cytoplasmic
4. Nuclear

Q. Write short note on
(a)Sex linkage (b) Crossing over (c)Sex chromosomes (d) Karyotype

Q. When red eyed males are crossed with white eyed females, one expects white eyed males and red eyed females in F₁ generation. However, Bridges found that sometimes, in such a cross, red eyed males and white eyed females could be observed. What was the reason for this observation?

1. Non-disjunction of X chromosomes
2. Epistasis
3. Codominance
4. Homologous recombination

Q. Linkage and crossing-over of genes are alternative of each other. Justify with the help of an example.

Q. A cross of a wild type red-eyed female Drosophila with a violet-eyed male produces all red-eyed offspring. If the gene is sex linked, what should the reciprocal cross(violet-eyed female x red-eyed male) produce? (Assume that the red allele is dominant to the violet allele).

1. All violet-eyed flies
2. $3$ red-eyed flies to $1$ violet-eyed
3. A $1:1$ ratio of red and violet eyes in both males and females
4. Red-eyed females and violet-eyed males

Q. Assertion :Sex-influenced genes are autosomal genes in both males and females. Reason: The phenotypic expression of sex-influenced genes is different in different sexes, dominant in one sex and recessive in the other.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
3. Assertion is correct but Reason is incorrect.
4. Both Assertion and Reason are incorrect.

Q. Criss cross inheritance discovered by Morgan, means

1. X chromosome from female will pass to female of next generation
2. X chromosome from male will pass to a male of next generation
3. Y chromosome from male will pass to a male of next generation
4. X chromosome from a male will pass to a female of next generation