Class 12 Sample Paper Biology (Half Yearly)

SAMPLE
PAPER
Half Yearly Examination

Prepared For
NCERT BASED SYLLABUS
Applicable For
CBSE BOARD AND STATE BOARD USING NCERT

WWW.

HALF YEARLY EXAMINATION
SAMPLE QUESTION PAPER

Class - XII Subject – Biology
Time – 3 Hours Maximum Marks- 70

General Instructions:-
(i) All questions are compulsory.
(ii) The question paper has four sections: Section A, Section B, Section C and Section D.
There are 33 questions in the question paper.
(iii) Section–A has 14 questions of 1 mark each and 02 case-based questions. Section–B
has 9 questions of 2 marks each. Section–C has 5 questions of 3 marks each and
Section–D has 3 questions of 5 marks each.
(iv) There is no overall choice. However, internal choices have been provided in
some questions. A student has to attempt only one of the alternatives in such questions.
(v) Wherever necessary, neat and properly labelled diagrams should be drawn.

SECTION-A
1. How many meiotic divisions are required to produce 44 seeds in a Mango fruit?
2. State the two factors responsible for conferring stability to double helix structure of DNA.
3. List two characteristics of mutation that help in explaining evolution as proposed by Hugo de
Vries.
4. A couple has two daughters. What is the probability that the third child will also be a daughter?
Give reason.
5. Write the physiological reason, why a woman generally cannot conceive a child after 50 years of
age?
6. Differentiate between the Homo habilis and Homo sapiens.
7. Mention any two applications of DNA fingerprinting.
8. State the two major tasks of RCH programmes.
9. What is the role of CaCl2 in preparation of competent cells?
10. Name the pattern of inheritance where F1 phenotype
(a) does not resemble either of the two parents and is in between the two.
(b) resembles only one of the two parents
11. Assertion: One of the two strands of DNA is called sense strand and other is called antisense
strand.
Reason: Sense strand of DNA forms complementary RNA.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

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12. Assertion: Very often persons suffering from sexually transmitted diseases (STDs) do not go
for timely detection and proper treatment.
Reason: Absence or less significant symptoms in the early stages of STDs and the social stigma
attached to the disease.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
OR
Assertion: Artificial insemination is method of introduction of semen inside the female.
Reason: This technique is used in those cases where males have low sperm count.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
13. Assertion: Darwin's finches of Galapagos Islands have different types of modified beaks
according to their food habits.
Reason: Adaptive radiation leads to development of different functional structure from a
common ancestral form.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
14. Assertion: In a monohybrid cross, F1 generation indicate dominant characters.
Reason: Dominance occurs only in heterozygous state.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
15. Read the following and answer any four questions from 15(i) to 15(v) given below:
Genes are segments of Deoxyribonucleic Acid (DNA) that contains the code for a specific
protein that functions in one or more types of cells in the body. Chromosomes are structures
within cells that contain a person’s genes. Genes are passed down the generations in a
particular manner and we receive roughly half our genetic material from each parent.
Chromosomes describe and determine gender and any changes in them causes chromosomal
abnormalities.
(i) The concept of chromosome movement during meiosis to explain Mendel’s laws was used
by
(a) Sutton and Boveri
(b) Malthus
(c) Correns
(d) T.H.Morgan
(ii) Crossing over in diploid organism is responsible for
(a) segregation of alleles
(b) recombination of linked genes

(c) dominance of genes
(d) linkage between genes

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(iii) If the genes are located in a chromosome as A-B-C-D-E-O-T. Which of the gene pairs will
have least probability of being inherited together?
(a) C and D
(b) A and T
(c) A and B
(d) O and T
(iv) Both chromosome and gene (Mendelian factors) whether dominant or recessive are
transmitted from one generation to next generation in
(a) changed form
(b) unaltered form
(c) altered form
(d) disintegrated form
(v) Assertion: Behaviour of chromosomes is parallel to gene.
Reason: Genes are located on the chromosomes.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of
Assertion.
16. Read the following and answer any four questions from 16(i) to 16(v) given below:
Selectable marker is a gene, which helps in selecting transformed host cells and eliminating
non-transformants. The process of selection of recombinants from non-recombinants occurs as
the transformants containing tetracycline resistant gene are plated on an ampicillin containing
medium. The mixture is then transferred on a medium containing tetracycline. The
recombinants will form colonies in ampicillin medium, but will not form colonies in
tetracycline medium. The non-recombinants will grow on both the mediums thus separating
out recombinants from non-recombinants. An alternative method used for the selection of
transformed cell is known as insertional inactivation.
(i) When an alien DNA is ligated in tetracycline resistant gene, the recombinant
(a) become tetracycline resistant
(b) will lose tetracycline resistant
(c) will remain same
(d) None of the above
(ii) In insertional inactivation, the recombinant DNA is inserted within the coding sequence of
(a) Beta-galactosidase
(b) tetracycline resistant gene
(c) restriction enzyme
(d) ampicillin resistant gene
(iii) Recombinant colonies in insertional inactivation are differentiated on the basis of
(a) production of blue colour
(b) production of no colour
(c) production of red colour
(d) production of green colour
(iv) Which of the following is/are function(s) of a selectable marker?
(a) Provides resistance against substrate

(b) Inhibits the growth of normal cell in a culture
(c) Helps to create a chromosome map
(d) Both (a) and (b)

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(v) Assertion: Selection of recombinants due to inactivation of antibiotics is cumbersome
cum
procedure.
Reason: It requires simultaneous plating on two plates having different antibiotics.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of
Assertion.
(d) Both
oth Assertion and Reason are false.

SECTION-B

17.

(a) Name the molecule ‘X’ synthesised by ‘i’ gene. How does this molecule get inactivated?
(b) When will the transcription of the structural genes stop?
18. Geitonogamous flowering plants are genetically autogamous but functionally cross-pollinated.
cross
Justify.
19. Name and state the role of the inner and middle walls of human uterus.
OR
Mention the sites of action of the hormones GnRH and FSH during spermatogenesis in human
males. Give one function of each of the hormone.
20. Explain with the help of a suitable example the naming of a restriction endonuclease.
21. How do ‘implants act as an effective method of contrcontraception
aception in human females? Mention its
one advantage over contraceptive pills.
22. Give reason
(a) Micropyle remains as a small pore in the seed coat of a seed.
(b)Apple
Apple and cashew are not called true fruits.
23. List the criteria of a molecule that can act as a genetic material must fulfill.
OR
(a) Differentiate between unambiguous and degenerate codons.
(b) Write two functions of the codon AUG.
24. STDs can be prevented by self-consciousness.
consciousness. Comment with two reasons.
25. Describe the neuroendocrine mechanism of parturition.

SECTION-C
26. Explain the processing the hnRNA needs to undergo before becoming functional mRNA in
eukaryotes.

27. How does Hardy-Weinberg’s
Weinberg’s expression explain that genetic equilibrium is maintained in a
population? List any two factors that can disturb the genetic equilibrium.

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28. Give reasons for the following observations:
(a) Genes for body colour and eye colour in Drosophila show less recombination frequency.
(b) Number of chromosomes is higher in female cockroach than in male cockroach.
(c) Possibility of a female becoming haemophilic is extremely rare.
OR
Write the reasons for which Mendel’s work was not recognised till 1900s.
29. Draw a diagram of pBR322 and label ori, ampR and rop. Also mention their roles.
30.Differentiate
tiate between convergent and divergent evolution. Give one example of each.

SECTION-D

31. In dogs, barking trait is dominant over silent trait & erect ears are dominant over drooping
ears. What is the expected phenotypic and genotypic ratio of the F2 progeny when dogs
homozygous for both the traits are crossed? State the law deduced by Mendel from this cross.
OR
(a) How does a chromosomal disorder differ from a Mendelian disorder?
(b) Name any two chromosomal aberration associated disorders.
(c) List the characteristics of the two disorders mentioned above.
32. The zygote passes through several developmental
develop stages till implantation. Describe
each stage briefly with suitable diagrams.
OR
Given below is the diagram of a human ovum surrounded by a few sperms. Study the diagram
and answer the following questions :

(a) Compare the fate of sperms shown in the diagram.
(b) What is the role of ‘D’ in this
is process?
(c) Analyze the changes occurring in the ovum during the process.
(d) How is the entry of sperm into the ovum facilitated ?
(e) Specify the region of female reproductive system where the event represented in the
diagram takes place.
33. (a) Explain the mechanism of DNA replication, highlight the role of enzymes in the process.
(b) Why is DNA replication said to be semiconservative?
OR
(a) Describe the various steps of Griffith’s experiment that led to the conclusion of the
‘transforming principle’.
(b) How did the chemical nature of the ‘transforming principle’ get established?

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