Mother and father of a person with '$O$' blood group have '$A$' and '$B$' blood group respectively. What would be the genotype of both mother and father ?
- Mother is homozygous for '$A$' blood group and father is heterozygous for '$B$'
- Mother is heterozygous for '$A$' blood group and father is homozygous for '$B$'
- Both mother and father are heterozygous for '$A$' and '$B$' blood group, respectively
- Both mother and father are homozygous for '$A$' and '$B$' blood group, respectively
The Correct Option is C
Solution and Explanation
Top Questions on Principles of Inheritance and Variation
- Assertion (A): A male individual always inherits haemophilia from his mother.
Reason (R): The gene for haemophilia lies on X-chromosome.- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
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:- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
- Which of the following conditions correctly describes the manner of determining the sex in the given options?
- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
- 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.
- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
Answer the following questions:
(a)
- What is a test cross? How can we find out the zygosity of a plant by the use of test cross?
- 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.
- Mention where in the cell these events take place.
- Explain the changes taking place during event ‘b’ and mention why these are needed.
- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
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.