CBSE Class 12th Biology Chapter 5 - Principles of Inheritance and Variation Important Questions with Answers

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Name the pattern of inheritance where F₁phenotype
(i) resembles only one of the two parents.
(ii) does not resemble either of the two parents and is in between the two. (All India 2019)
Or
Name the respective pattern of inheritance, where F₁ phenotype
(i) does not resemble either of the two parents and is in between the two.
(ii) resembles only one of the two parents. (All India 2012)

Question 2.

British geneticist RC Punnett developed a graphical representation of a genetic cross called ‘Punnett Square’. Mention the possible result this representation predicts of the genetic cross carried. (Delhi 2019)

Question 3.

Explain polygenic inheritance with the help of an example. (All India 2019)

Question 4.

Explain the phenomena of dominance, multiple allelism and codominance taking human ABO blood group as an example. (All India 2019)

Question 5.

Compare in any three ways the chromosomal theory of inheritance as proposed by Sutton and Bovery with that of experimental results on pea plant presented by Mendel. (Delhi 2019)

Question 6.

(i) Explain linkage and recombination as put forth by TH Morgan based on his observations with Drosophila melanogaster crossing experiment.
(ii) Write the basis on which Alfred Sturtevant explained gene mapping. (Delhi 2019)

Question 7.

(i) Work out the crosses so as to obtain the phenotypic ratios given below:
(a) 1 : 2 : 1 (in F₂-generation)
(b) 3 : 1 (in F₂-generation)
(c) 1 : 1 (in F₁-generation)
(ii) Differentiate between pleiotropy and polygenic inheritance patterns. (All India 2019)

Question 8.

Differentiate between incomplete dominance and codominance. Substantiate your answer with one example of each. (Delhi 2019)

Question 9.

Write the genotypes of the parents of a child suffering from thalassemia. State the cause of this disease. (All India 2019)

Question 10.

Name a disorder a human suffers from as a result of monosomy of the sex chromosome. Give the karyotype and write the symptoms. (All India 2019)

Question 1.

Name the kind of diseases/disorders and any two symptoms that are likely to occur in humans if
(i) Mutation in the gene that codes for an enzyme phenylalanine hydroxylase occurs.
(ii) the karyotype is XXY. (All India 2019)
Or
(i) Name the kind of diseases/disorders that are likely to occur in humans if
(a) mutation in the gene that codes for an enzyme phenylalanine hydrolase occurs,
(b) there is an extra copy of chromosome 21,
(c) the karyotype is XXY.
(ii) Mention any one symptom of the diseases/disorders named above. (Foreign 2015)

Question 2.

(i) Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with for their experiments.
Explain the correlation between linkage and recombination with respect to genes as studied by them.
(ii) How did Sturtevant explain gene mapping while working with Morgan? (2018)

Question 3.

Write the sex of a human having XXY chromosome With 22 pairs of autosomes. Name the disorder this human suffers from. (2018C)

Question 4.

Name the type of cross that would help to find the genotype of a pea plant bearing violet flowers. (All India 2017)

Question 5.

State the fate of a pair of autosome during gamete formation. (Delhi 2017)

Question 6.

During a medical investigation, an infant was found to possess an extra chromosome 21. Describe the symptoms the child is likely to develop later in the life. (Delhi 2017)
Or
Explain how trisomy of 21st chromosome occurs in humans. List any four characteristic features in an individual suffering from it. (Foreign 2012)
Or
Name the genetic disorder caused by trisomy of 21st chromosome in a human. Write the diagnostic features of the disorder. (Delhi 2011C)

Question 7.

Both haemophilia and thalassemia are blood related disorders in humans. Write their causes and the difference between the two. Name the category of genetic disorder they both come under. (All India 2017)

Question 8.

State a difference between a gene and an allele. (All India 2016)

Question 9.

Give an example of polygenic trait in humans. (Delhi 2016C)
Or
On what basis is the skin colour in humans considered polygenic? (Delhi 2016)

Question 10.

Although Mendel published his work on inheritance of characters in 1865 but for several reasons, it remained unrecognised till 1900. Explain giving three reasons, why did it take so long. (Delhi 2016C)
Or
Mendel published his work on inheritance of characters in 1865, but it remained unrecognised till 1900. Give three reasons for the delay in accepting his work. (Delhi 2014)