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Cryptorchidism is a… (Class 12 Biology SQP 2024-25, Q31A)

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BiologyCBSE Class 12 · Sample paper, session 2024-25 · 5 marks · Long answer

CBSE Class 12 Biology sample paper 2024-25: question 31(A)

From the official CBSE sample question paper for 2024-25, section E, question 31(A), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q31(A) · 5 marks · Long answerCompetency-basedHuman Reproduction

Cryptorchidism is a condition in which the testes fail to descend into the scrotum. It can also lead to compromised Sertoli cell function and has an impact on Leydig cell function.
(i) Identify at least 3 parameters of male fertility which get affected due to cryptorchidism.
(ii) Which process will be affected if mature spermatids are not released from Sertoli cells?
(iii) Name and explain one assisted reproductive technology (ART process) in which the sperm/semen is used to assist fertilization.
(iv) Name and explain the assisted reproductive technology that should be used to complete the development of embryos I and II shown in the figure given below.

Figure in the paper: Two embryos: Embryo I with 8 blastomeres and Embryo II with 16 blastomeres, each a circle containing cells with nuclei; blastomeres labelled. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

Open one hint at a time and try again before the next.

Hint 1

Consider what Sertoli cells and Leydig cells each do in the testis.

Hint 2

Release of sperms from Sertoli cells has a specific name.

Hint 3

For (iv), the number of blastomeres decides whether the embryo goes to the fallopian tube or the uterus.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (i) Testes kept at body temperature (higher than scrotal temperature) cannot function normally, so:

    • Sperm count falls, because spermatogenesis is impaired.
    • Spermiogenesis is affected, because faulty Sertoli cells cannot nourish spermatids to become spermatozoa.
    • Androgen (testosterone) secretion falls, because the Leydig cells are affected.
    1½ marks

  2. (ii) If mature spermatids (sperms) are not released from the Sertoli cells, spermiation is affected.

    ½ mark

  3. (iii) Artificial insemination (AI): semen from the husband or a healthy donor is artificially introduced into the vagina or into the uterus (IUI – intra-uterine insemination) of the female. It is used when the male cannot inseminate or has a low sperm count.

    (Alternatively, ICSI – intra-cytoplasmic sperm injection: a sperm is injected directly into the ovum to form an embryo in the laboratory.)

    1 mark

  4. (iv) Embryo I (8 blastomeres): use ZIFT (zygote intra-fallopian transfer). The zygote or early embryo with up to 8 blastomeres is transferred into the fallopian tube to complete its development.

    1 mark

  5. (iv) Embryo II (16 blastomeres): use IUT (intra-uterine transfer). An embryo with more than 8 blastomeres is transferred into the uterus to complete its development.

    1 mark

Answer: (i) Reduced sperm count/spermatogenesis, impaired spermiogenesis, reduced androgen secretion; (ii) Spermiation; (iii) AI/IUI (or ICSI); (iv) Embryo I – ZIFT; Embryo II – IUT.

Where the marks are

  • Any three fertility parameters affected: sperm count/spermatogenesis, spermiogenesis, androgen secretion (0.5 × 3 = 1.5 marks)
  • Names spermiation (0.5 mark)
  • Names and explains AI/IUI or ICSI (1 mark)
  • ZIFT for the 8-blastomere embryo, with explanation (1 mark)
  • IUT for the 16-blastomere embryo, with explanation (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Human Reproduction, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2024-25: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.