AI-generated explanation. Check against your textbook.
Explanation:
Pleiotropism means one gene affecting many phenotypic traits. So option 4 is correct. A single gene influences multiple features such as color, height, and metabolism in some organisms as described in NCERT discussions of gene action.
🧠 Did You Know?
In pleiotropy, a single mutant gene can cause multiple symptoms or disorders, illustrating how genes can have widespread effects beyond one trait.
💡 NCERT Memory Line:
A single gene may influence more than one character (pleiotropy).
Frequency of recombination between gene pairs on same chromosome as a measure of the distance between genes to map their position on chromosome, was used for the first time by:
Which of the following statements are correct about
Klinefelter's Syndrome?
A. This disorder was first described by Langdon Down (1866).
B. Such an individual has overall masculine development. However, the feminine development is also expressed.
C. The affected individual is short stature.
D. Physical, psychomotor and mental development is retarded.
E. Such individuals are sterile.
Choose the correct answer from the options given below:
Given below are two statements: Statement I: Mendel studied seven pairs of contrasting traits in pea plants and proposed the Laws of Inheritance. Statement II: Seven characters examined by Mendel in his experiment on pea plants were seed shape and colour, flower colour, pod shape and colour, flower position and stem height.
In the light of the above statements, choose the correct answer from the options given below:
AI-generated explanation. Check against your textbook.
Explanation:
Statement I is correct: Mendel studied seven pairs of contrasting traits in pea plants and proposed the Laws of Inheritance. Statement II is also correct: the seven characters examined were seed shape and seed colour, flower colour, pod shape and pod colour, flower position, and stem (plant) height. These together constitute seven distinct traits described by NCERT. Hence, option 1 is the right choice.
🧠 Did You Know?
NCERT mentions seven contrasting characteristics studied by Mendel, which laid the foundation for the Laws of Inheritance (dominant/recessive, segregation, and independent assortment).
💡 NCERT Memory Line:
Mendel studied seven pairs of contrasting characters in peas and formulated the basic laws of inheritance.
AI-generated explanation. Check against your textbook.
Explanation:
XO type sex determination means males have one X chromosome (X0) and no second sex chromosome, while females have two X chromosomes (XX). This system is seen in grasshoppers and some other insects, where the male is the heterogametic sex with a single X. Therefore, option 3 (Grasshoppers) is correct. In Drosophila, birds, and monkeys, different systems operate: Drosophila uses an XY system, birds use a ZW system for females, and monkeys (humans) use an XY system as well. The NCERT description of XO is specifically linked to grasshoppers.
🧠 Did You Know?
In XO species, the sex chromosomes are not a pair in males; the presence of only one X determines maleness, while females have two X chromosomes.
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Mendel’s law of Independent assortment does not hold good for the genes that are located closely on the same chromosome. Reason (R): Closely located genes assort independently.
In the light of the above statements, choose the correct answer from the options given below:
If a colour blind female marries a man whose
mother was also colour blind, what are the chances
of her progeny having colour blindness?
AI-generated explanation. Check against your textbook.
Explanation:
Color blindness is an X-linked recessive trait. A color-blind female has genotype XbXb. If she marries a color-blind man (mother color-blind makes him XbY), their children will inherit Xb from the father and Xb from the mother for daughters (XbXb) and Xb from the mother with Y from the father for sons (XbY). Thus all offspring will be color blind. Therefore the chances are 100% (option 3).
🧠 Did You Know?
NCERT states that color blindness is an X-linked recessive trait, so it is passed through X chromosomes and often affects males more commonly.
💡 NCERT Memory Line:
Color blindness is an X-linked recessive trait; a color-blind female (XbXb) crossed with a color-blind male (XbY) yields color-blind offspring of all sexes.
