Genetics Practice Questions and Answers

For any question, any combination of True or False is possible (i.e. all answers may be True, all answers may be False, or some may be True and some False).

 

1. A mouse, true-breeding for brown fur is crossed with a mouse, true-breeding for  white fur. All of the offspring are beige. The F2 generation segregate, 25% with brown fur, 50% with beige fur and 25% with white fur. 

A. Two genes regulating coat colour are segregating
B. Brown and white show intermediate dominance 
C. Brown is dominant to white
D. The brown and white mice differ in a single gene 
E. Complementation has occurred

2. In fruit flies, the enzyme Xanthine dehydrogenase synthesises the red eye pigment. Mutations in  the gene encoding  this enzyme inactivate it, causing white eye colour. The gene is carried on the X chromosome. 

When a male fly from a true-breeding white-eyed stock is crossed with a female from a true-breeding red-eyed stock......

A. The white-eyed phenotype will be dominant to red-eyed
B. The F1 generation will comprise red-eyed males and white-eyed females 
C. A test-cross of F1 males (to recessive females) will produce white-eyed male and red- eyed female progeny 
D. A test-cross of F1 females (to recessive males) will produce a 1:1 ratio of red: white eyes regardless of gender 
E. An F2 generation would comprise 50% red-eyed females, 25% red-eyed males and 25% white-eyed males

3. A true-breeding womble with brown eyes and blue fur is crossed with a true-breeding womble with black eyes and green fur. All the F1 progeny had black eyes and blue fur. These progeny were then crossed with wombles from a true-breeding, brown-eyed, green furred line. The following progeny were obtained:  60 brown eyes, blue fur; 71 black eyes green fur, 19 brown eyes, green fur; 25 black eyes blue fur. 

A. The true-breeding stocks differ genetically in two genes
B. The crosses between the F1 and the brown-eyed, green furred wombles are test-crosses
C. The brown-eye allele is in coupling with the green fur allele
D. The recombination frequency between the fur colour and eye colour genes is 25.1%
E. A recombination frequency of 25% or more means that the genes are on separate chromosomes

4. Which statements are True and which are False?

A. Strain 1 and Strain 6 are mutant in the same red pigment-formation gene
B. Strain 3 and Strain 8 are mutant in the same red pigment-formation gene
C. Strain 2 and Strain 9 are mutant in different red pigmentation genes
D. Red colour in the progeny of  the cross between Strain 5 and Strain 6 is the result of transformation
E. Red colour in the progeny of the cross between Strain 5 and Strain 6 is the result of complementation

5. Which statements are True and which are False?

A.  Mutations in Strains 3, 10 and 1 are allelic
B.  Mutations in strains 7, 9 and 1 are allelic
C.  If the red (F1) progeny of the cross between Strain 1 and Strain 2 are selfed to give an F2 generation, the predicted ratio of progeny would be 3 red: 1 white
D.  If the red (F1) progeny of the cross between Strain 1 and Strain 2 are selfed to give an F2 generation, the predicted ratio of progeny would be 1 red: 1 white
E.  If the red (F1) progeny of the cross between Strain 1 and Strain 2 are selfed to give an F2 generation, the predicted ratio of progeny would be 9 red: 7 white