PCAT Biological Processes – Dihybrid Cross
- Jan 03, 2018
- PCAT Question of the Day
For a particular plant, straight leaves result from a dominant gene (L) and wrinkled leaves result from a recessive gene (l), and tall height results from a dominant gene (T) while short height results from a recessive gene (t). A dihybrid cross is performed with plants heterozygous for both traits. What is the expected ratio of short, straight-leaved plants to tall, straight-leaved plants?
Click for Explanation
In a dihybrid cross, the genes for two traits are crossed in a Punnett square. For two heterozygotes crossed in a Punnett square, the expected ratio of recessive/recessive, dominant/recessive, recessive/dominant, to dominant is 1:3:3:9. In this particular question, the ratio of both recessive/dominant to dominant/dominant is 1:3.
A) 1:1, incorrect.
B) 1:2, incorrect.
C) 1:3, correct, This ratio is shown above by the ratio of blue genotypes to orange genotypes.
D) 3:1, incorrect.
Search the Blog
Free ConsultationSchedule Now
MCAT Blog How to Review MCAT Full-Lengths
Free MCAT Practice AccountNeed great MCAT practice?
Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.Learn More