List of top Biology Questions on Principles of Inheritance and Variation

A normal couple produces half the sons as haemophilic and half the daughters as carriers. Choose the option that correctly indicates the chromosome on which the gene for this trait is located.

Answer the following questions with respect to the sex determining mechanism observed in honey bee.

  • [(a)] Name the type of sex determination system observed in honey bee.
  • [(b)] Fill in the blanks (i), (ii) and (iii) in the given question.

  • [(c)] What will be the sex and chromosome number of the progeny formed from the unfertilised eggs of honey bee?
What are chromosomal disorders? Describe Turner's syndrome and Klinefelter's syndrome.
What are the reasons for the success of Mendel?
What is the genotype of Drosophila showing normal wings?
If a colour-blind woman marries a person whose mother is colour-blind, then what is the probability of colour blindness in their offspring?

The sequence of nitrogenous bases in a segment of a coding strand of DNA is 
5' – AATGCTAGGCAC – 3'. Choose the option that shows the correct sequence of nitrogenous bases in the mRNA transcribed by the DNA.

A man with blood group AB marries a woman with blood group O. What is the probability that their child will have blood group A?

1. Perform a cross between two sickle cell carriers. What ratio is obtained between carrier, disease free and diseased individuals in F1 progeny? Name the nitrogenous base substituted, in the haemoglobin molecule in this disease.
2. Explain the difference in inheritance pattern of flower colour in garden pea plant and snap-dragon plant with the help of monohybrid crosses.
OR,
Explain with the help of well-labelled diagrams how lac operon operates in E. coli :
1. In presence of an inducer.
2. In absence of an inducer.

Study the pedigree chart given below, showing the inheritance pattern of blood group in a family:

Answer the following questions:
(a) Give the possible genotypes of individual 1 and 2.
(b) Which antigen or antigens will be present on the plasma membranes of the R.B.Cs of individuals ‘5’ and ‘8’?

A man whose father was colour-blind marries a woman who had a colour-blind mother and normal father. What percentage of male children of this couple will be colour-blind?
Genes which control $\alpha$-Thalassemia and $\beta$-Thalassemia are present on which number of chromosomes?
In humans, non-disjunction of the 21st pair of chromosomes leads to:

In a certain population, the frequency of three genotypes is as follows:
Genotypes: PP Pp  pp 
Frequency: 22%  62%  16% 
Choose the option that shows the frequency of P and p alleles correctly:

Assertion (A): A male individual always inherits haemophilia from his mother.
Reason (R): The gene for haemophilia lies on X-chromosome.
Which of the following conditions correctly describes the manner of determining the sex in the given options?
Assertion (A): Human male is referred to as heterogametic.
Reason (R): The male produces millions of sperms of the same kind.

Answer the following questions:

(a)

  1. What is a test cross? How can we find out the zygosity of a plant by the use of test cross? 
  2. Why are human females rarely haemophilic? Explain with the help of a cross. Under what conditions can a haemophilic female be born? How do haemophilic patients suffer? 

OR 
(b) Name the two events ‘a’ and ‘c’ shown in the diagram below. 

 

  1. Mention where in the cell these events take place. 
  2. Explain the changes taking place during event ‘b’ and mention why these are needed.
Answer the following questions:
  • Write the scientific name of the fruit fly.
  • Why did Morgan prefer to work with fruit flies for his experiments? State two reasons.
A dwarf pea plant was treated with gibberellic acid and it becomes as tall as a tall pea plant. If these treated pea plants are crossed with pure tall pea plants, the phenotypic ratio in $F_1$ generation will be:

A karyotype of a human suffering from a certain disorder is given below:

Answer the following:

  • [(a)] Identify the disorder.
  • [(b)] Write the symptoms of the disorder.
  • [(c)] Give reason for such a disorder.
Assertion (A): A male individual always inherits haemophilia from his mother.
Reason (R): The gene for haemophilia lies on X-chromosome.
Which of the following conditions correctly describes the manner of determining the sex in the given options?
Name one commonly occurring genetic disorder in humans which is caused due to monosomy (one chromosome less than the normal number of chromosomes) of sex chromosome. Give its two symptoms.
In a pea plant (Pisum sativum), green pod colour is dominant over yellow pod colour. The expected ratio of the phenotypes of the offsprings (F$_1$) in a cross between parents with heterozygous green pod colour and homozygous yellow pod will be: