When two heterozygous tall plants TT is crossed the F1 generation will have both tall and dwarf plants give the genotypic ratio of this cross?

Free

10 Questions 10 Marks 10 Mins

The correct answer is 1: 1.

• '​Pure' plants refer to the homozygous condition in plants and 'hybrid' refers to the heterozygous plants.
• Homozygous - It is the condition in which the pair of alleles determining a phenotype is identical, either both dominant (TT) or both recessive (tt).
• Heterozygous - It is the condition where 2 different types of alleles are present, one dominant and one recessive (Tt).
• When a pure tall plant (TT) is crossed with a pure short plant (tt), the F1 generation produces heterozygous tall (Tt) plants.
• Upon selfing the F1 generation, that is, crossing two heterozygous tall plants, the following numbers of the F2 generation are obtained phenotypically:
  • Three tall plants and one short plant
• Whereas, genotypically, the following ratio is obtained:
  • One pure tall plant, two heterozygous tall plants, and one pure short plant.
• Therefore, considering the genotype, the ratio of pure tall plants to pure short plants in the F2 generation is 1:1. Hence, Option 1 is correct.

• Please note here that the question asks about the ratio of "pure" tall plants to short plants in F2 generation.
• The usual ratio of 3:1 is for "all" tall plants to short plants.
• Pure Tall plants : Hybrid Tall plants : Short/Dwarf plants = TT : Tt : tt = 1:2:1
• Therefore, Pure tall : Pure short = 1:1

Ace your General Science and Biology preparations for Genetics and Evolution with us and master Mendelian Genetics for your exams. Learn today!

India’s #1 Learning Platform

Start Complete Exam Preparation

Daily Live MasterClasses

Practice Question Bank

Mock Tests & Quizzes

Get Started for Free Download App

Trusted by 3.3 Crore+ Students

Text Solution

`375,125``250,250``475,25``350,150`

Answer : A

Solution : The crossing between two heterozygous plants is as follows <br> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/NCERT_FING_BIO_OBJ_XII_PIV_C05_E01_012_S01.png" width="80%"> <br> So, if plants obtained were 500, then the respective number of tall and dwarf plants will be 375 tall and 125 dwarf.