CBSE 12 Biology Question Paper-2025 Set-6

The 'beads' in the extended 'beads-on-string' form of chromatin are composed of:

The 'string' in the 'beads-on-string' form of chromatin represents:

In its extended 'beads-on-string' form of chromatin, the 'beads' in the string represent:

The statements below are related to the accessory ducts of the human male reproductive system:
(i) Seminiferous tubules of the testis open into vasa efferentia through rete testis which lead to vas deferens.
(ii) Vasa efferentia leave the testis and open into epididymis.
(iii) The epididymis leads to vas deferens which ascends to the abdomen.
(iv) Vas deferens receives a duct from the seminal vesicle and opens into the urethra as the ejaculatory duct.
(v) The urethra extends through the penis and its external opening is called urethral meatus.
Choose the correct statement from the given options:

Some statements regarding oogenesis in human females are given below:
(i) Unequal division of primary oocyte results in the formation of a large secondary oocyte and a tiny first polar body.
(ii) Oogonia are formed during embryonic development of a female fetus.
(iii) Oogonia divide by mitosis and enter prophase-I of meiotic division.
(iv) A large number of primary oocytes degenerate during the period from birth to puberty.
(v) A primary oocyte completes meiosis II on fertilization.
Choose the option with the correct statements:

Some statements regarding the process of oogenesis in human females are given below:
(i) Oogonia are formed and added after birth.
(ii) Oogonia start division and enter the prophase-I stage of meiotic division.
(iii) At puberty, only 60,000-80,000 primary follicles are left in each ovary.
(iv) The first meiotic division is completed after fertilization.
(v) The second meiotic division is completed only on fertilization.
Choose the option with the correct statements:

Meiosis II occurs during the division of:

Some statements regarding spermatogenesis are given below:
(i) It starts at puberty due to the significant increase in the secretion of GnRH.
(ii) It occurs in the seminiferous tubules of the testis.
(iii) The spermatogonia divide mitotically and meiotically to form the haploid spermatids.
(iv) Spermatids are transformed into spermatozoa by the process of spermiogenesis.
(v) Luteinizing Hormone (LH) acts on Sertoli cells and stimulates the secretion of androgens.
Choose the correct statements from the given options:

A man with blood group A marries a woman with blood group B. They have a son with blood group O. What will be the genotype of the parents?

Study the given pedigree chart of a family and identify the nature of the trait:

Choose the correct option:

What is the genotype of the parents of the affected male in the I generation?

Choose the correct option:

The ratio of phenotypes of a monohybrid cross, if the trait shows incomplete dominance, is:

In a pedigree analysis chart ☐ ☐ represents:

The name of the scientist who proposed the principle that the flow of genetic information in molecular biology is unidirectional is:

Which of the following characteristics correctly expresses the mechanism of sex determination in honeybees? (i) Zygote is formed by the fusion of a sperm and an ovum (male). (ii) The number of chromosomes in a male (drone) is half the number of chromosomes in a female honeybee. (iii) Female honeybees are diploid with 32 chromosomes. (iv) Male honeybees have fathers and can produce male progeny. Choose the correct option:

The male accessory glands of humans include:

Which of the following is a symptom of Gonorrhoea?

Which of the following sexually transmitted diseases is caused by a protozoan?

In a pedigree chart, if a trait appears in every generation, it is:

The flow of genetic information from DNA to RNA and protein is known as the:

In a human male, the meiotic division to form sperm cells takes place in the:

Which of the following is an example of an inducible operon?

Which of the following organisms is not a host for a retrovirus?

What is the function of the enzyme reverse transcriptase?

Which of the following is not a characteristic of a retrovirus?

Which of the following is an example of a sexually transmitted disease caused by a virus?

Which of the following is a symptom of Gonorrhoea?

Which of the following is a sexually transmitted disease caused by a protozoan?

The male accessory glands of humans include:

In a pedigree chart, if a trait appears in every generation, it is:

The flow of genetic information from DNA to RNA and protein is known as the:

In a human male, the meiotic division to form sperm cells takes place in the:

The male accessory glands of humans include:

Which of the following is a symptom of Gonorrhoea?

Which of the following sexually transmitted diseases is caused by a protozoan?

In a pedigree chart, if a trait appears in every generation, it is:

The flow of genetic information from DNA to RNA and protein is known as the:

In a human male, the meiotic division to form sperm cells takes place in the: