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Science (English Medium) Class 12 - CBSE Important Questions

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A pregnant human female was advised to undergo MTP. It was diagnosed that the fetus she was carrying had developed from a zygote having 45 chromosomes with only one X chromosome.

  1. What is this condition called and how does it arise?
  2. Why was she advised to undergo MTP?
Appears in 1 question paper
Chapter: [3] Reproductive Health
Concept: Induced Abortion or Medical Termination of Pregnancy (MTP)

With the help of a flow chart, illustrate how an infected animal cell can survive while viruses are being replicated or released.

Appears in 1 question paper
Chapter: [3] Reproductive Health
Concept: Sexually Transmitted Diseases (STD) or Sexually Transmitted Infections (STI)

Placed below are case studies of some couples who were not able to have kids. These couples are not ready for adoption or taking gametes from donors. After thoroughly examining the cases, which Assisted Reproductive Technology will you suggest to these couples as a medical expert? Explain briefly with justification of each case.

Couple Test reports of
Female partner
Test reports of male partner
Couple 1 Normal reports Normal sperms in testes, Missing connection
in epididymis and Vas deferens.
Couple 2 Blockage in the fallopian tube Normal reports
Couple 3 Normal reports Poor semen parameters in terms of count,
motility and morphology.
Couple 4 low ovarian reserve Normal reports
Couple 5 Sterilization in male Morphologically abnormal sperms
Appears in 1 question paper
Chapter: [3] Reproductive Health
Concept: Infertility

Given below are certain situations. Analyse the situation and suggest the name of suitable contraceptive device along with mode of action.

Situation Requirement of contraceptive for - Name of contraceptive device Mode of action
1 blocking the entry of sperms through cervix ______ ______
2 spacing between children ______ ______
3 effective emergency contraceptive ______ ______
4 terminal method to prevent any more pregnancy in female ______ ______
5 sterilization in male ______ ______
Appears in 1 question paper
Chapter: [3] Reproductive Health
Concept: Birth Control

A male honeybee has 16 chromosomes whereas its female has 32 chromosomes. Give one reason.

Appears in 1 question paper
Chapter: [4] Principles of Inheritance and Variation
Concept: Chromosomal Theory of Inheritance

Explain the relationship between CFC’s and Ozone in the stratosphere.

Appears in 1 question paper
Chapter: [4] Environmental Issues
Concept: Ozone Layer Depletion >> Ozone Depletion in the Stratosphere

Name any two sources of e-Wastes and write two difference ways of their disposal.

Appears in 1 question paper
Chapter: [4] Environmental Issues
Concept: Radioactive Waste Management and E-waste

How have human activities caused desertification? Explain.

Appears in 1 question paper
Chapter: [4] Environmental Issues
Concept: Degradation by Improper Resource Utilisation and Maintenance

State the difference between meiocyte and gamete with respect to chromosome number.

Appears in 1 question paper
Chapter: [4] Principles of Inheritance and Variation
Concept: Chromosomal Theory of Inheritance

Differentiate between male and female heterogamety.

Appears in 1 question paper
Chapter: [4] Principles of Inheritance and Variation
Concept: Sex Determination

Differentiate between ‘ZZ’ and ‘XY’ type of sex-determination mechanisms.

Appears in 1 question paper
Chapter: [4] Principles of Inheritance and Variation
Concept: Sex Determination

Name the type of cell division involved in the production of sperms by honey bees.

Appears in 1 question paper
Chapter: [4] Principles of Inheritance and Variation
Concept: Chromosomal Theory of Inheritance

Why did T. H. Morgan select Drosophila melanogaster to study sex linked genes for his lab experiments ?

Appears in 1 question paper
Chapter: [4] Principles of Inheritance and Variation
Concept: Sex Determination

Name the pollutant attributed to be the cause of ‘ozone-hole’ over the Antarctica region.

Appears in 1 question paper
Chapter: [4] Environmental Issues
Concept: Ozone Layer Depletion >> Ozone Depletion in the Stratosphere

List the greenhouse gases other than carbon dioxide.

Appears in 1 question paper
Chapter: [4] Environmental Issues
Concept: Greenhouse Effect and Climate Change

What is heterogamety ? Explain the mechanism of sex determinatin in Drosophila.

Appears in 1 question paper
Chapter: [4] Principles of Inheritance and Variation
Concept: Sex Determination

How would you find out whether a given tall garden pea plant is homozygous or heterzygous? Substantiate your answer with the help fo Punnett squares.

Appears in 1 question paper
Chapter: [4] Principles of Inheritance and Variation
Concept: Monohybrid Cross

Given below are the F2 – phenotypic ratios of two independently carried monohybrid crosses :
(i) 1 : 2 : 1
(ii) 3 : 1
Mention what does each ratio suggest.

Appears in 1 question paper
Chapter: [4] Principles of Inheritance and Variation
Concept: Monohybrid Cross

Answer the following question.
Name the layer of the atmosphere that is associated with ‘good ozone’.

Appears in 1 question paper
Chapter: [4] Environmental Issues
Concept: Ozone Layer Depletion >> Ozone Depletion in the Stratosphere

Answer the following question.
Write the basis on which Alfred Sturtevant explained gene mapping.

Appears in 1 question paper
Chapter: [4] Principles of Inheritance and Variation
Concept: Monohybrid Cross
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