Ask a Doubt
Request a call back

Join NOW to get access to exclusive study material for best results

CBSE Class 10 Answered

When is a recessive trait capable of expressing itself? Write the expression using contasting trait of height in plants.(5 marks)
Asked by sajal2402 | 02 Feb, 2019, 04:27: PM
answered-by-expert Expert Answer
  • A recessive trait is capable of expressing itself when it is present in the homozygous condition.
  • Consider pea plants having a pair of contrasting characters namely, tallness and dwarfness with respect to the height of the stem.
  • The parental generation P1 has the genotype TT for a pure tall parent plant and tt for a pure dwarf plant.
  • The two parents are homozygous, having one type of gamete each, i.e. T from tall parent and t from the dwarf parent. These two plants are crossed with one another.
  • All plants in first filial or F1 generation were tall. The F1 generation has genetic constitution Tt.
  • It is genotypically a hybrid and a heterozygous plant having two different alleles. Phenotypically, the plant is tall because the allele or the gene T for tallness masks the effect of its corresponding recessive gene t.
  • F1 plants are self-pollinated to obtain F2 generation. Now, each of these parents is heterozygous tall with genotype Tt. So, we have Tt × Tt. The gametes produced from each of the parents are of two types, T and t.
  • The second filial generation F2, has a genotypic ratio of 1 TT : 2 Tt : 1 tt. As in this case, allele T for tallness is dominant, the pea plants with genotype Tt will be tall.
  • The phenotypic ratio is 3 tall : 1 dwarf. Genotypically, it shows 3 types of plants: 1 TT, which is homozygous tall, 2 Tt which are heterozygous tall and 1 tt which is homozygous dwarf. Thus, the genotypic ratio is 1 TT : 2 Tt : 1 tt.
  • In this way, we could see that in F1 generation since the recessive allele t for dwarfness was in heterozygous condition, it was not able to express itself and the plants obtained were not dwarf. However, in F2 generation, since the recessive allele was in homozygous conditions (tt) it could express itself and the plant obtained was dwarf. 
Answered by Sheetal Kolte | 04 Feb, 2019, 11:01: AM

Application Videos

Concept Videos

Multiple Choice Questions Practice Test
Answered Unanswered My Questions My Answers
CBSE 10 - Biology
1+1
question image
Asked by sathishkumar.sk6680 | 26 Jan, 2024, 09:35: AM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Biology
mono hybridisation
Asked by vramesh.kumar1804 | 09 Jan, 2024, 10:34: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Biology
what is hereditary
Asked by navinkumar785790 | 17 Jun, 2023, 10:33: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Biology
Two human beings who can both roll their tongues produced 11 children. 3 of these children could not roll their tongues and 8 children could roll their tongues. (a) Which trait (rolling or not rolling) is controlled by the recessive allele? (b) State all possible genotypes of the F1 generation of the cross. Show the inheritance of the tongue rolling in humans in the given example using a suitable cross. What percentage of offspring will show the same genotype as the parents? OR (c) If one of the parents could not roll their tongue, with the help of a cross, calculate the ratio of tongue- rollers to non-tongue-rollers in the off springs.​
Asked by Venkata Raman | 06 Feb, 2023, 06:59: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Biology
In human, the allele for brown eyes (B) is dominant over that for blue eyes (b). A brown eyed woman marries a blue eyed man, and they have six children. Four of the children are brown eyed and two of them are blue eyed. a) What is the genotype of blue eyes offspring? b) What is the woman's genotype? c) Mention the above process of inheritance in a flow chart.
Asked by swetalinasamantaray022 | 29 Dec, 2022, 01:27: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Biology
explain law of inheritance
Asked by nitusinghparihar309 | 26 Dec, 2022, 09:32: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Biology
importance of variation?
Asked by blessybhatia09 | 17 Apr, 2022, 10:47: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Biology
a man with blood group A ,black color hair is crossed with woman with blood group O , brown colour hair show the monohybrid cross
Asked by srestasingh7 | 26 Dec, 2021, 10:36: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Biology
why is DNA copying an essential part of the process of reproduction
Asked by bhadouriarakesh9917 | 02 Mar, 2021, 08:44: AM
ANSWERED BY EXPERT ANSWERED BY EXPERT
CBSE 10 - Biology
which of the process sexual reproduction or Asexual Reproduction bring about maximum variation in the offspring
Asked by abhay2006ji | 22 Dec, 2020, 03:46: PM
ANSWERED BY EXPERT ANSWERED BY EXPERT
My Class Videos Tests ₹ Plans Ask a Doubt
Get Latest Study Material for Academic year 24-25 Click here
×