Please refer to Principles of Inheritance and Variation Class 12 Biology Important Questions with answers below. These solved questions for Chapter 5 Principles of Inheritance and Variation in NCERT Book for Class 12 Biology have been prepared based on the latest syllabus and examination guidelines issued by CBSE, NCERT, and KVS. Students should learn these solved problems properly as these will help them to get better marks in your class tests and examinations. You will also be able to understand how to write answers properly. Revise these questions and answers regularly. We have provided Notes for Class 12 Biology for all chapters in your textbooks.

Important Questions Class 12 Biology Chapter 5 Principles of Inheritance and Variation

All Principles of Inheritance and Variation Class 12 Biology Important Questions provided below have been prepared by expert teachers of Standard 12 Biology. Please learn them and let us know if you have any questions.

Question. Explain the mechanism of sex determination in honeybees
Answer : Haplo-Diploid-unfertillised eggs become males, fertilized eggs become females.

Question. Write the scientific name of the organism which T.H. Morgan used in his genetic experiments.
Answer : Drosophila melanogaster

Question. Give the characteristic features of Turner’s Syndrome.
Answer : Female sterile with rudimentary overies, lack other sexual characters. XO

Question. Who had proposed the chromosomal theory of inheritance?
Answer : Sutton & Boveri

Question. What will be the genotype and phenotype of the offspring if a colour blind man marriesa carrier woman?
Answer : Manwith Xcfemalewithone Xcandexplanationthroughflowchart

Question. List the advantages of selecting pea plant for his experiments by Mendel
Answer : Bisexual, one season breeding, contrasingtraits

Question. What is pedigree analysis, how is it useful?
Answer : Method of analyzing inheritance of traits in humans. Study inheritance of diseases for genetic counselling

Question. Tabulate the different types of sex determination in organisms.
Answer : XX female, XY male, ZZ male, ZW female, XO male, XX female

Question. Themalefruitflyandfemalefowlareheterogametic,whilethefemalefruitflyandthe Male fowl are homogametic why are they termed so.
Answer : Produce dissimilar gametes-heterogametic, produce similar gametes-they are homogametic

Question. Define and explain testcross
Answer : Cross between dominant phenotype of unknown genotype with the recessive plant. Ratio 1:1 shows genotype of dominant plant as hetrozygous.

Question. With the help of an example differentiate between incomplete dominance and co-dominance.
Answer : Neither of the hetrozygous pair expressed completely Eg. Mirabilis sp. Both the alternative forms are expressed when found together Eg. blood groups.

Question. State the difference between a gene and an allele.
Answer : Alleles are different forms of a gene

Question. Write the possible genotypes Mendel got when he crossed F1 Tall pea plants with a dwarf pea plant.
Answer : Tall and dwarf

Question. How does the Mandelian disorder phenylketonuriaoccur?
Answer : Inborn error of metabolism-lacks enzyme for converting phenyl alanine to tyrosine. Phenyl pyruvic acid is excreted

Question. Briefly mention the contributions of T.H.Morgan in genetics
Answer : Experiments with Drosophila-linkage & recombination

Question. Explain law of dominance with an example.
Answer : When a pair of heterozygous alleles seen together, the allele which is expressed is the dominant one. Tt Tall plants produced

Question. What is a point mutation, give an example
Answer : Change of a single nitrogen base, Eg. Sickle cell amaemia

Question. Why did Mendel select garden pea plant for his experiments?
Answer : Short life span, only 4 pairs of chromosomes, distinct male & female traits, cultured in the lab

Question. Anita was happy when she gave birth to her first child. Her in- laws were dissatisfied at her not givingbirthtoamalechildandblamedAnita.Anitatriedtoconvinceherinlawsthatshehadno role in the child’s gender. They understood the biological reason but were yet to be satisfied. Anita’s husband took up the matter and convinced the parents.
a) What values did Anita’s husband show in the above situation?
b) What governs sex determination in humans? How is it different from birds?
c) Why can’t Anita be blamed for not giving birth to a male child?
Answer : (a) Strong and determined personality with responsibility towards the family and respect for elders.  
(b) Sex chromosomes. In human males it is XY and in female it is XX In birds, male is ZZ while female is ZW.
(c) Human femals are homogametic i.e. produces only one type of gametes containing 22+X choromosome only. Males are hetrogametic and produce two types of gametes 22+X and 22+Y. It is the type of the male gamete which determines the sex of the foetus. If X chromosome containing spaerm fuses with the egg, it produces a female child whereas if Y chromosome containing sperm fuses with the egg, it produces a male child.