ABO blood group system is due to
- multifactor inheritance
- incomplete dominance
- multiple allelism
epistasis
The Correct Option is C
Solution and Explanation
Some genes can have more than two alleles. When a trait is controlled by more than two alleles, it is called multiple allelism. In humans, the blood group is determined by three alleles (IA, IB and IO) of a gene I. A person can only have two of the three alleles, determining his blood group. Person with both IA alleles belongs to A blood group, IAIB to AB blood group and B group for both IB alleles. Similarly, persons with O blood group have both alleles Io.
The other three options are incorrect as they do not account for the blood group in humans.
- Multifactor Inheritance - It refers to the trait or disease caused by more than one factor like birth defect, chronic illness etc.
- Incomplete Dominance - The condition in which the two alleles of a gene are partially expressed resulting in a different phenotype not seen in parents, is called incomplete dominance.
- Epistasis - It is a condition in which the expression of a gene is inhibited due to the presence of another gene.
Top Questions on Principles of Inheritance and Variation
Assertion (A): In dihybrid crosses involving sex-linked genes in \(\textit{Drosophila}\), generation of non-parental gene combinations are observed
Reason (R): Two genes present on different chromosomes show linkage and recombination in \(\textit{Drosophila.}\)- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
Explain how the addition of lactose in the medium regulates the switching on of the \(\textit{lac}\) operon in bacteria.
- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
Assertion (A) : In dihybrid crosses involving sex-linked genes in \(\textit{Drosophila}\), \(F_2\) generation of non-parental gene combinations are observed.
Reason (R) : Two genes present on different chromosomes show linkage and recombination in \(\textit{Drosophila.}\)- CBSE CLASS XII - 2025
- Biology
- 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.
- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
- In a pedigree chart, if two unaffected individuals have a child with the trait, what is the most likely mode of inheritance for this trait ?
- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
Questions Asked in NEET exam
- A microscope has an objective of focal length \(f_o = 2\) cm and an eyepiece of focal length \(f_e = 4\) cm. The tube length of the microscope is \(L = 40\) cm. If the distance of distinct vision of eye is \(D = 25\) cm, the magnification in the microscope is:
- NEET (UG) - 2025
- Optical Instruments
- Read the following statements on plant growth and development:
A. Parthenocarpy can be induced by auxins. B. Plant growth regulators can be involved in promotion as well as inhibition of growth. C. Dedifferentiation is a pre-requisite for re-differentiation. D. Abscisic acid is a plant growth promoter. E. Apical dominance promotes the growth of lateral buds.- NEET (UG) - 2025
- Plant Physiology
- Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus.
Reason (R): Presence of more than one nucleus in the tapetum increases the efficiency of nourishing the developing microspore mother cells.- NEET (UG) - 2025
- Reproduction in Plants
- With the help of the given pedigree, find out the probability for the birth of a child having no disease and being a carrier (has the disease mutation in one allele of the gene) in the F3 generation.
- NEET (UG) - 2025
- Genetics
Consider a water tank shown in the figure. It has one wall at \(x = L\) and can be taken to be very wide in the z direction. When filled with a liquid of surface tension \(S\) and density \( \rho \), the liquid surface makes angle \( \theta_0 \) (\( \theta_0 < < 1 \)) with the x-axis at \(x = L\). If \(y(x)\) is the height of the surface then the equation for \(y(x)\) is: (take \(g\) as the acceleration due to gravity)
- NEET (UG) - 2025
- Surface Tension
NEET Notification
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.