Briefly mention the contribution of T.H. Morgan in genetics.
Solution and Explanation
Top Questions on Principles of Inheritance and Variation
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.- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
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.- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
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’?- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
- 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?
- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
- What is the genotype of Drosophila showing normal wings?
- MHT CET - 2025
- Biology
- Principles of Inheritance and Variation
Questions Asked in CBSE CLASS XII exam
Bittu and Chintu were partners in a firm sharing profit and losses in the ratio of 4 : 3. Their Balance Sheet as at 31st March, 2024 was as follows:
On 1st April, 2024, Diya was admitted in the firm for \( \frac{1}{7} \)th share in the profits on the following terms:- (i) New profit sharing ratio between Bittu, Chintu and Diya was 3 : 3 : 1 .
- (ii) Fixed Assets were found to be overvalued by ₹ 1,40,000.
- (iii) Creditors were paid ₹ 4,20,000 in full settlement.
- (iv) Diya brought proportionate capital and ₹ 5,60,000 as her share of goodwill premium by cheque.
Prepare Revaluation Account and Partners' Capital Accounts.
- CBSE CLASS XII - 2025
- Partnership Accounts
- Pass the necessary journal entries for the following transactions on the dissolution of a partnership firm of Vibha and Ajit after various assets (other than cash) and external liabilities have been transferred to Realisation Account:}
Creditors worth ₹ 46,000 accepted ₹ 9,000 cash and furniture of ₹ 32,000 in full settlement of their claim.
The firm had stock of ₹ 20,000. Ajit took over 40% of the stock at a discount of 10% while the remaining stock was sold for ₹ 18,000.
Vibha was appointed to look after dissolution work for which she was allowed a remuneration of ₹ 16,000. Vibha agreed to bear the dissolution expenses. Actual dissolution expenses ₹ 15,000 were paid by Vibha.
Ajit’s loan of ₹ 45,000 was settled at ₹ 42,000.
A machine which was not recorded in the books was taken over by Vibha at ₹ 23,000, whereas its expected value was ₹ 28,000.
The firm had a debit balance of ₹ 20,000 in the Profit and Loss Account on the date of dissolution.- CBSE CLASS XII - 2025
- Dissolution of Partnership Firms
- How does the process of Natural Selection affect Hardy-Weinberg equilibrium? Explain with the help of graphs.
- CBSE CLASS XII - 2025
- evolution
- A battery of emf \( E \) and internal resistance \( r \) is connected to a rheostat. When a current of 2A is drawn from the battery, the potential difference across the rheostat is 5V. The potential difference becomes 4V when a current of 4A is drawn from the battery. Calculate the value of \( E \) and \( r \).
- CBSE CLASS XII - 2025
- Current electricity
- An electric dipole of dipole moment \( 1.0 \times 10^{-12} \ \text{Cm} \) lies along the x-axis. An electric field of magnitude \( 2.0 \times 10^4 \ \text{NC}^{-1} \) is switched on at an instant in the region. The unit vector along the electric field is \( \frac{\sqrt{3}}{2} \hat{i} + \frac{1}{2} \hat{j} \). The magnitude of the torque acting on the dipole at that instant is:
Concepts Used:
Chromosomal Theory of Inheritance
Chromosomal theory: Linkage and Genetic Recombination
If two genes were present on the same chromosome, the chances of getting a parental combination were much higher in the next generation in comparison to the non-parental combination. This physical association of genes was termed ‘linkage’. The description of the non-parental gene combinations in a dihybrid cross is termed ‘genetic recombination'. After the discovery of linked genes, the frequency of linked genes also influenced the appearance of traits in the next generation.
Observations of Chromosomal Theory of Inheritance:
- During the cell division-meiosis process, the pairs of homologous chromosomes move as discrete structures, which are independent of other pairs of chromosomes.
- From each homologous pair, there is a random distribution of chromosomes into the pre-gametes.
- Each parent synthesizes gametes, which add up to only half of their chromosomal complement.
- Even though female (egg) and male (sperm) gametes differ in morphology and size, they have the same number of chromosomes, submitting equal genetic contributions from each parent.
- The gametic chromosomes fuse during the process of fertilization to produce offspring with the same number of a chromosome as their parents.
Read More: Chromosomal Theory of Inheritance