XO type of sex determination can be found in
- Drosophila
- Birds
- Grasshoppers
- Monkeys
The Correct Option is C
Solution and Explanation
Grasshoppers serve as a classic example of organisms exhibiting the XO sex determination system. In this system, males possess only one X chromosome (XO), while females have two X chromosomes (XX). Thus, the absence of the Y chromosome in males differentiates this system from the XY system commonly found in humans and other mammals.
By analyzing the options provided:
- Drosophila: Employs the XY system for sex determination, where males have both an X and a Y chromosome.
- Birds: Utilize the ZW system, where males are ZZ and females are ZW.
- Grasshoppers: Exhibit the XO system, with males characterized by an XO configuration and females by an XX configuration.
- Monkeys: Similar to humans, exemplify the XY system, where males are XY and females are XX.
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
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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
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Answer the following questions:
(a)
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OR
(b) Name the two events ‘a’ and ‘c’ shown in the diagram below.
- Mention where in the cell these events take place.
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Predict the major product $ P $ in the following sequence of reactions:
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(iii) Na(Hg), $C_{2}H_{5}OH$- NEET (UG) - 2025
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AB is a part of an electrical circuit (see figure). The potential difference \(V_A - V_B\), at the instant when current \(i = 2\) A and is increasing at a rate of 1 amp/second is:
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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.