Which one of the following conditions though harmful in itself, is also a potential saviour from a mosquito borne infectious disease:
- Thalassaemia
- Sickle cell anaemia
- Pernicious anaemia
- Leukemia
The Correct Option is B
Solution and Explanation
Sickle cell anemia is a genetic disorder caused by a mutation in the hemoglobin gene. While it is a harmful condition in itself and can cause various health problems, individuals with sickle cell trait (heterozygous for the gene) are less susceptible to contracting malaria, a mosquito-borne infectious disease. This is because the sickled red blood cells are less favorable for the malaria parasite's growth and survival. Therefore, in regions where malaria is prevalent, having the sickle cell trait can provide some level of resistance to the disease, which is why it's considered a potential savior from malaria. However, it's essential to note that sickle cell anemia itself is a severe health condition with its own set of complications.
So, the correct option is (B): Sickle cell anaemia
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 NEET exam
A bob of heavy mass \(m\) is suspended by a light string of length \(l\). The bob is given a horizontal velocity \(v_0\) as shown in figure. If the string gets slack at some point P making an angle \( \theta \) from the horizontal, the ratio of the speed \(v\) of the bob at point P to its initial speed \(v_0\) is :
- NEET (UG) - 2025
- Pendulums
A full wave rectifier circuit with diodes (\(D_1\)) and (\(D_2\)) is shown in the figure. If input supply voltage \(V_{in} = 220 \sin(100 \pi t)\) volt, then at \(t = 15\) msec:
- NEET (UG) - 2025
- Semiconductor Diode
- The correct order of the wavelength of light absorbed by the following complexes is:
A. $[ \text{Co(NH}_3\text{)}_6]^{3+}$
B. $[ \text{Co(CN)}_6]^{3-}$
C. $[ \text{Cu(H}_2\text{O)}_4]^{2+}$
D. $[ \text{Ti(H}_2\text{O)}_6]^{3+}$
Choose the correct answer from the options given below:- NEET (UG) - 2025
- Coordination chemistry
- A uniform rod of mass 20 kg and length 5 m leans against a smooth vertical wall making an angle of \(60^\circ\) with it. The other end rests on a rough horizontal floor. The friction force that the floor exerts on the rod is (take \(g = 10\) m/s\(^2\)):
- NEET (UG) - 2025
- Common forces in mechanics
A constant voltage of 50 V is maintained between the points A and B of the circuit shown in the figure. The current through the branch CD of the circuit is :
- NEET (UG) - 2025
- Current electricity
Concepts Used:
Principles of Inheritance and Variation - Mutation
A Mutation is a change in the sequence of our DNA base pairs caused by numerous environmental stimuli such as UV light or mistakes during DNA replication. Germline mutations take place in the eggs and sperm and can be passed onto offspring, whereas somatic mutations take place in body cells and are not passed on.
Types of Mutations
There are three types of mutations, which are as follows:
Silent mutation
It refers to any change in DNA sequence that has no effect on the amino acid sequence in a protein or the functions that a protein performs. There is no phenotypic indication that a mutation has occurred.
Nonsense mutation
When there is a change in the sequence of base pairs due to a point mutation, that results in a stop codon. This leads to a protein that is either shortened or non-functional.
Missense mutation
A missense mutation occurs when a point mutation causes a change in the codon, which then codes for another amino acid.
The mutation is caused by the following factors:
Internal Causes
When DNA copies incorrectly, the majority of mutations occur. Evolution occurs as a result of all of these mutations. DNA makes a copy of itself during cell division. When a copy of DNA isn't flawless, it's called a mutation since it differs somewhat from the original DNA.
External Causes
When certain chemicals or radiations are used to break down DNA, it causes the DNA to break down. The thymine dimers are broken by UV radiation, resulting in altered DNA.