Class 12 PT I Question Paper 2025-26 Biology

PERIODIC TEST
QUESTION
PAPER
PT1 - PT2

BASED P
T A
ER

P
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NC

S

Directions: In the following questions, a statement of assertion is

followed by a statement of reason.
Mark the correct choice as:
(a) If both Assertion and Reason are true and Reason is the correct
explanation of Assertion.
(b) If both Assertion and Reason are true but Reason is not the correct
explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.

(ii). Asertion: Barrier methods prevent physical meeting of sperms and
ova.
Reason: This prevents conception.
Assertion: After bleeding phase of menstrual cycle proliferative stage starts.
Reason:After bleeding phase repauir and proliferation of endometrial lining
occurs.

How does Cu-T act as an effective contraceptive for human

females?
A woman has certain queries as listed below, before starting with

contraceptive pills. Answer them.
(i)What do contraceptive pills contain and how do they act as
contraceptives?
(ii)What schedule should be followed for taking these pills?

Answer the following questions: (3)
(i) At which stage of menstrual cycle progesterone level remains highest?
(ii)On 15 – 17 day level of LH remains very high. Which term is used for this
condition? What is the importance of this condition?
(iii) What happens with the empty graafian follicle? What is the importance of
it?

1 1

2 What can be the blood group of offspring when both parents have AB blood group ? 1
(a) AB only(b) A, B and AB(c) A, B, AB and O(d) A and B only

3 The correct sequence of hormone secretion from beginning of menstruation is 1
A. FSH, progesterone, estrogen.
B. estrogen, FSH, progesterone.
C. FSH, estrogen, progesterone.
D. estrogen, progesterone, FSH.

4 ZZ / ZW type of sex determination is seen in 1
(a) Platypus
(b) Snails
(c) Cockroach
(d) Peacock

5 Colour blindness is 1
(a) Z chromosome linked trait

1 1

(b) X-linked trait
(c) Y-linked trait
(d) Both X and Y linked

6 1
Diaphragms are contraceptive devices used by females. Read the statements given below with
respect to diaphragms and choose the correct statements.

I. They act as physical barriers to sperm entry.
II. They even prevent the spread of STIs.
III. They are placed to cover the cervical region.
IV. They act as spermicidal agents.
V. Their use is associated with an increased urinary tract infection.

a. I, II, III and IV b. II, III, IV and V c. II, IV and V D. I, III and V

Directions: In the following questions, a statement of assertion is

1 1

followed by a statement of reason.
Mark the correct choice as:
(a) If both Assertion and Reason are true and Reason is the correct
explanation of Assertion.
(b) If both Assertion and Reason are true but Reason is not the correct
explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false

7 Assertion: When white eyed, yellow bodied Drosophila females were hybridized with red eyed, 1
brown-
bodied males; and F1 progeny was intercrossed, F2 ratio deviated from 9 : 3 : 3 : 1.

Reason: When two genes in a dihybrid are on the same chromosome, the proportion of parental
gene

combinations is much higher than the non-parental

8 Assertion: Barrier methods prevent physical meeting of sperms and ova. 1

1 1

Reason: This prevents conception.

9 Assertion: After bleeding phase of menstrual cycle proliferative stage starts. 1
Reason:After bleeding phase repair and proliferation of endometrial lining occurs.

10 Assertion: In birds, sex is determined by the male bird. 1
Reason: Female bird produces two types of genetically different egg containing either Z or W sex
chromosome.

SECTION B

11 Thalassemia is an autosomal recessive disorder that causes anaemic conditions in an 2
individual. A blood smear from a heterozygous individual shows blood cells that are small, pale and
irregularly

shaped along with normal RBCs.
(a) State the genotypic and phenotypic ratios of offspring born to a carrier mother and a thalassemic
father.
(b) Does the allele for thalassemia exhibit codominance? Justify

1 1

12 A woman has certain queries as listed below, before starting with 2

contraceptive pills. Answer them.
(i)What do contraceptive pills contain and how do they act as
contraceptives?
(ii)What schedule should be followed for taking these pills?

13 The pedigree chart given below shows a particular trait which is absent in parents but present in the 2
next generatoin irrespective of sexes. Draw your conclusion on the basis of the pedigree

1 1

14 List the three different allelic forms of gene ‘I’ in humans. Explain the different phenotypic 2
expressions, controlled by these three forms.
SECTION C

15 (i) At which stage of menstrual cycle progesterone level remains highest? 3
(ii)On 15 – 17 day level of LH remains very high. Which term is used for this
condition? What is the importance of this condition?
(iii) What happens with the empty graafian follicle? What is the importance of
it?

16 Explain Tubectomy and Vasectomy with Diagram? 3

17 a) Identify the disorder. 3

b) Write the symptoms of the disorder.
c) Give the reason for the disorder.

1 1

18 With the help of an example differentiate between incomplete dominance and co-dominance. 3

SECTION D

19 The graph given below shows the variation in the levels of ovarian hormones during various phases 5
of menstrual cycle:

1 1

(i) Identify A and B
(ii) Specify the source of the hormone marked in the diagram.
(iii) Reason out: why A peaks before B ?
(iv) Compare the role of A and B.
(v) Under which condition will the level of B continue to remain high on the 28th day?

20 The F2 progeny of a monohybrid cross showed phenotypic and genotypic ratio as 1 : 2 : 1, 5
unlike that of Mendel’s monohybrid F2 ratio. With the help of a suitable example, work out a
cross and explain how it is possible.

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