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(i) A blood test… (Class 12 Biology SQP 2024-25, Q17A)

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BiologyCBSE Class 12 · Sample paper, session 2024-25 · 2 marks · Very short answer

CBSE Class 12 Biology sample paper 2024-25: question 17(A)

From the official CBSE sample question paper for 2024-25, section B, question 17(A), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q17(A) · 2 marks · Very short answerCompetency-basedHuman Reproduction

(i) A blood test reported negative for hCG. What does negative hCG imply? Name the tissue which produces hCG?
(ii) If a blood test reported positive for hCG in a person, then which other hormones would also be secreted by the tissue secreting hCG?

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

hCG is a hormone that appears in blood only after implantation.

Hint 2

Which temporary endocrine tissue forms between the embryo and the uterine wall?

Hint 3

That tissue also makes lactogen, relaxin and steroid hormones.

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) hCG is secreted only once an embryo has implanted, so a negative hCG test means the person is not pregnant.

    ½ mark

  2. (i) hCG (human chorionic gonadotropin) is produced by the placenta.

    ½ mark

  3. (ii) A positive hCG test means a placenta is present. Besides hCG, the placenta also secretes human placental lactogen (hPL), estrogens, progestogens and relaxin. Any two of these are enough.

    1 mark

Answer: (i) Negative hCG means no pregnancy; hCG is produced by the placenta. (ii) hPL, estrogens, progestogens, relaxin (any two).

Where the marks are

  • States that negative hCG means no pregnancy (0.5 mark)
  • Names placenta as the tissue producing hCG (0.5 mark)
  • Names any two other placental hormones: hPL, estrogens, progestogens, relaxin (0.5 × 2 = 1 mark)

Revise the chapter

  • Chapter: Human Reproduction (notes, formulas, where marks are lost and every past question)
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.