Test: Class 12 Biology: CBSE Sample Question Paper- Term I (2021-22)


60 Questions MCQ Test Sample Papers for Class 12 Medical and Non-Medical | Test: Class 12 Biology: CBSE Sample Question Paper- Term I (2021-22)


Description
Attempt Test: Class 12 Biology: CBSE Sample Question Paper- Term I (2021-22) | 60 questions in 90 minutes | Mock test for Class 12 preparation | Free important questions MCQ to study Sample Papers for Class 12 Medical and Non-Medical for Class 12 Exam | Download free PDF with solutions
QUESTION: 1

In the figure of anatropous ovule given below, choose the correct option for the characteristic distribution of cells within the typical embryo sac 

Solution:

At the micropylar end out of the four nuclei, only three differentiate into two synergids and one egg cell. Together they are known as egg apparatus.  The egg apparatus consists of 2 synergids and one egg cell. The synergids have special cellular thickenings at the micropylar tip. These are together called the filiform apparatus. It helps to guide the pollen tubes into the synergid. Similarly, at the chalazal end, three out of the four nuclei differentiate as antipodal cells.  The remaining two cells (of the micropylar end and the chalazal end) move towards the center and are known as polar nuclei, which are situated in a large central cell.  Hence, at maturity, a typical mature angiosperm embryo sac (the female gametophyte) appears as a 7-celled structure, though it has 8-nucleate.

QUESTION: 2

The coconut water from tender coconut is

Solution:

The tender coconut water is a free-nuclear endosperm (made up of thousands of nuclei) and the surrounding white kernel is the cellular endosperm.

QUESTION: 3

Pollen grains are well preserved as fossils because of presence of

Solution:

Pollen grains are well preserved as fossils due to the presence of sporopollenin. Sporopollenin is a highly resistant organic material, which can withstand high temperature and strong acids and alkali. Enzymes cannot degrade sporopollenin.

QUESTION: 4

Which of the following statements are true related to Seed X and Y ?

(i) Seed X is dicot and endospermic or albuminous.
(ii) Seed X is dicot and non-endospermic or non-albuminous.
(iii) Seed Y is monocot and endospermic or albuminous.
(iv) Seed Y is monocot and non-endospermic or non-albuminous.
Choose the correct option with the respect to the nature of the seed:

Solution:

The seed X is dicot and is non-endospermic whereas seed Y is monocot and is endospermic.

QUESTION: 5

Which of the following statements are correct with respect to hormones secreted by placenta?
(i) Placenta secretes relaxin during later stage of pregnancy
(ii) Placenta secretes high amount of FSH during pregnancy
(iii) Placenta secretes relaxin during initial stage of pregnancy
(iv) Placenta secretes hCG and hPL during pregnancy

Solution:

Placenta acts as an endocrine gland by secreting Human chorionic gonadotropin (hCG), human placental lactogen (hPL), oestrogens, progesterone and relaxin.

QUESTION: 6

Figure A shows the front view of the human female reproductive system and Figure B shows the development of a fertilized human egg cell:
Figure A 

Figure B

Identify the correct stage of development of human embryo (Figure B) that takes place at the site X, Y and Z respectively in the human female reproductive system (Figure A).
Choose the correct option from the table below:

Solution:

The label X represent uterus. Blastocyst gets attached at this site. The label Y is the fallopian tube where the process of fertilisation takes place. The label Z represents ovaries where egg is produced by the process of oogenesis. 

QUESTION: 7

Penetration of the sperm in the ovum is followed by:

Solution:

Penetration of the sperm in the ovum is followed by completion of meiosis II.

QUESTION: 8

The correct sequence of hormone secretion from beginning of menstruation is:

Solution:

The correct sequence of hormone secretion from beginning of menstruation is  FSH, estrogen, and progesterone. 

QUESTION: 9

In the dioecious aquatic plant shown, identify the characteristics of the male flowers that reach the female flowers for pollination:

Solution:

In the dioecious aquatic plant shown, the flowers are small and white in colour. The pollen grains have a mucilaginous covering to protect from wetting.

QUESTION: 10

The thalamus contributes to the fruit formation in:

Solution:

Such fruits are called false fruits.

QUESTION: 11

How many types of gametes would be produced if the genotype of a parent is AaBB ?

Solution:

Two type of gametes will be produced: AB and aB.

QUESTION: 12

Which of the following statements indicates parallelism in genes and chromosomes ?
(i) They occur in pairs
(ii) They segregate during gamete formation
(iii) They show linkage
(iv) Independent pairs segregate independently

Solution:

Walter Sutton and Theodor  Boveri in  1902. They discovered that behaviour of chromosomes was parallel to behaviour of genes. Chromosome and genes both occur in pair. The two alleles of a gene pair are located on homologous sites of homologous chromosomes.

QUESTION: 13

Which of the following amino acid substitution is responsible for causing sickle cell  anemia ?

Solution:

Sickle cell anaemia involves mutation in a single base pair in the beta globin chain of haemoglobin pigment in the blood. Glutamic acid in short arm of chromosome II gets replaced with valine at the sixth position.

QUESTION: 14

In human beings, where genotype AABBCC represents dark skin colour, aabbcc represents light skin colour and AaBbCc represents intermediate skin colour; the pattern of genetic inheritance can be termed as :

Solution:

In human beings, where genotype AABBCC represents dark skin colour, aabbcc represents light skin colour and AaBbCc represents intermediate skin colour; the pattern of genetic inheritance can be termed as polygenic and quantitative inheritance.

QUESTION: 15

Which of the following combination of chromosome numbers represents the correct sex determination pattern in honey bees ?

Solution:

The female are diploid having 32 chromosomes and males are haploid i.e. having 16 numbers of chromosomes.

QUESTION: 16

Rajesh and Mahesh have defective haemoglobin due to genetic disorders. Rajesh has too few globin molecules while Mahesh has incorrectly functioning globin molecules. Identify the disorder they are suffering from:

Solution:

Rajesh is suffering from thalassemia. Thalassemia is an autosomal recessive disorder of the red blood cells.  In Thalassemia one of the components of the haemoglobin molecule is inadequately produced or not produced at all. Mahesh, on the other hand is suffering from sickle cell anemia, which is an autosome linked recessive disorder. It is caused by point mutation in the beta-globin chain of haemoglobin pigment of the blood.

QUESTION: 17

Which of the following criteria must a molecule fulfil to act as a genetic material ?
(i) It should not be able to generate its replica.
(ii) It should chemically and structurally be stable.
(iii) It should not allow slow mutation.
(iv) It should be able to express itself in the form of Mendelian Characters.

Solution:

A genetic material should

  • Be able to generate its replica (Replication).
  • Be chemically and structurally stable.
  • Provide the scope for slow changes (mutations) that are required for evolution.
  • Be able to express itself as ‘Mendelian Characters’.
QUESTION: 18

The promoter site and the terminator site for transcription are located at :

Solution:

The promoter site and the terminator site for transcription are located at 5′ (upstream) end and 3′ (downstream) end, respectively of the transcription unit 

QUESTION: 19

Which of the following is correct about mature RNA in eukaryotes ?

Solution:

The primary transcript (hn RNA) contain both exons and introns and required to be processed before they become translationally active (mRNA). The introns are removed by a process called RNA processing or RNA splicing.

QUESTION: 20

In E.coli, the lac operon gets switched on when :

Solution:

In presence of lactose (inducer), it binds with repressor protein and inactivates it. So repressor protein cannot bind to operator gene. The operator gene becomes free and induces the RNA polymerase to bind with promoter gene. Hence, three structural genes express their product and respective enzymes are produced. These enzymes act on lactose so that lactose is metabolized into glucose and Galactose.

QUESTION: 21

Oswald Avery, Colin MacLeod and Maclyn McCarty used enzymes to purify biochemicals such as proteins, DNA and RNA from the heat-killed S cells to see which ones could transform live R cells into S cells in Griffith's experiment. They observed that

Solution:

Oswald Avery, Colin MacLeod and Maclyn McCarty. They worked to determine the biochemical nature of ‘transforming principle’ in Griffith’s experiment. They discovered that

  • DNA alone is transformed.
  • Proteases and RNases did not affect transformation.
  • Digestion with DNase inhibited transformation, suggesting that the DNA caused the transformation.
QUESTION: 22


AUG on the mRNA will result in the activation of which of the following RNA having correct combination of amino acids:

Solution:

AUG is the initiation codon for methionine. So methionyl tRNA complex would have UAC at the Anticodon site.

QUESTION: 23

Short stretches of DNA used to identify complementary sequence in a sample are called

Solution:

Short stretches of DNA used to identify complementary sequence in a sample are called probes.

QUESTION: 24

The structure of bilobed anther consists of

Solution:

Anther is a sac-like structure that produces pollen grains. It is bilobed and each lobe has two theca i.e. dithecous.

QUESTION: 25

Direction: Consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:

Assertion (A) : Chargaff rule is applicable to RNA.
Reason (R) : RNA contains deoxyribose sugar in them.

Solution:

Lactational amenorrhea is a natural method of contraception and  involves the prevention of conception by breast feeding the child.

QUESTION: 26

Direction: Consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:

Assertion (A) :  The mammary glands secrete milk for the nourishment of the young.
Reason (R) : These are modified sweat glands.

Solution:

Saheli is a non-steroidal preparation used as oral contraceptive pills. It is a ‘once a week’ pill with very few side effects and high contraceptive value.

QUESTION: 27

Direction: Consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:

Assertion (A) :  The primary sex organs are the structures that produce gametes.
Reason (R) : The primary sex organs located within the pelvic cavity and the secondary sex organs are the external genitalia.

Solution:

Parturition is a neuroendocrine mechanism and is started by the signals from the developed foetus and the placenta. The signals originating from the foetus and placenta induce mild uterine contractions (fetal ejection reflex). This causes the release of oxytocin from maternal pituitary. Oxytocin causes stronger uterine muscle contractions which in turn stimulate further secretion of oxytocin. This process is continued leading to expulsion of the baby out of the uterus through the birth canal.

QUESTION: 28

Direction: Consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:

Assertion (A) : Aminoacylation is an essential step for the synthesis of protein.
Reason  (R) : It is the process of adding an activated amino acid to the acceptor arm of a transfer RNA.

Solution:

When two genes are located on the same chromosome, the proportion of parental gene combinations was much higher than the non-parental type. Morgan attributed this due to the physical association or linkage of the two genes and coined the term linkage.

QUESTION: 29

If the haploid number of chromosomes in a plant species is 20, how many chromosomes will be present in the cells of the shoot tip?

Solution:

Placenta is connected to the embryo by an umbilical cord. It transports substances to and from the embryo.

QUESTION: 30

A criminal blew himself up in a local market when he was chased by cops. His face was beyond recognition. Suggest a modern technique that can help establish his identity.

Solution:

In a fertilized ovule, antipodal cells are haploid (n), zygote is diploid  (2n)  while endosperm is triploid (3n).

QUESTION: 31

 If a genetic disease is transferred from a phenotypically normal but carrier female to only some of the male progeny, the disease is

Solution:

The flower type which survived is Cleistogamous and it always exhibits autogamy. Cleistogamous flowers do not open at all. They have closed anthers and stigma, that lies close to each other. 

QUESTION: 32

A mother is advised to breastfeed her baby in the first hour after birth. This provides a baby protection against infection and disease.The first breastmilk  is called?

Solution:

During parturition, a pregnant woman is having prolonged labour pains and child birth has to be fastened. It is advisable to administer a hormone that can activate smooth muscles of myometrium of the uterus, which directs the full term foetus towards the birth canal.

QUESTION: 33

Conditions of a karyotype 2n ± 1 and 2n ± 2 are called  

Solution:

IVF treatment technique is done to give birth test tube baby. The in vitro fertilisation of male and female gamete occurs outside the body and then it is cultured upto 8 blastomeres. After that it is transferred in the female body for further development.

QUESTION: 34

Pollen grain has two male gametes. How many pollen grains will be required to fertilize 10 ovules present in a particular carpel?

Solution:

IUDs increase phagocytosis of sperms. The Cu ions suppress motility and fertilising capacity of sperms.

QUESTION: 35

Carefully examine structures A and B of pentose sugar given below. Which one of the two is more reactive?

Solution:

The meiotic division is involved in the formation male and the female gamete. The formation of the male gamete requires only one meiotic division which results in four male gametes. The formation of four female gametes, on the other hand requires four meiotic divisions. So, the five meiotic divisions result in four seeds. Thus 500 meiotic divisions result in 400 seeds.

QUESTION: 36

A geneticist interested in studying variations and patterns of inheritance in living beings.He should prefer to choose organisms for experiments with

Solution:

Out of 9:3:3:1 = 16
9+3 will be tall.
Therefore, 12/16 x 80 = 60. 

QUESTION: 37

In a woman's life when menopause occurs, she is unable to conceive a child. The reason could be:

Solution:

The phenotypic ratio in F1 generation when a cross is performed between RR X Rr will be 2 red (RR) and 2 Pink (Rr).

QUESTION: 38

During replication, the two strands unwind and separate by breaking _(i)____ bonds in the presence of an enzyme,__(ii)_____ The separated strands act as_____(iii)____for the synthesis of new strands. DNA replicates in the ____(iv)___direction.

Solution:

In the monohybrid cross, a test cross of a heterozygous individual resulted in a 1:1 ratio.

QUESTION: 39

A colour blind boy is born to a couple with a normal colour vision.The genotype of the parents will be

Solution:

 The pattern of inheritance in the above pedigree chart is autosomal recessive.

QUESTION: 40

Select the correct statement:
(1) Method of sterilization in males is Vasectomy.
(2) Fallopian tubes of both sides are cut and tied in tubectomy.
(3) Sterilization is very effective method as it blocks gamete transport.
(4) Test tube babies are same as normal babies.

Solution:

The probability that the third child will also be a female will be 50 %.

QUESTION: 41

About 300 million spermatozoa may be present in a human male ejaculation at one time.How many spermatocytes will be involved to produce 300 spermatozoa.

Solution:

A cross of two F1 hybrids, that are heterozygous for a single trait and that displays incomplete dominance is predicted to give a 1:2:1 ratio among both the genotypes and phenotypes of the offspring.

QUESTION: 42

In human female, what happens to corpus luteum in human female if the ovum is not fertilized?

Solution:

It can be concluded that is a single stranded DNA.

QUESTION: 43

After a brief medical examination a healthy couple came to know that both of them are unable to produce functional gametes and should look for an ‘ART’ (Assisted Reproductive Technique). Name the ‘ART’ that you can suggest to them to help them bear a child.

Solution:

A typical nucleosome contains about 200 base pairs (bp) of the DNA helix.
So if a stretch of an euchromatin has 200 nucleosomes, there will be 200 × 200 = 40,000 base pairs in the stretch. Also, the length of the typical euchromatin will be 13,600 x10-9 m

QUESTION: 44

In Snapdragon, a cross between true breeding red flower (RR) plants and true breeding white flower (rr) plants showed a progeny of plants with all pink flowers. The appearance of pink flowers is not known as blending because

Solution:

Presence of 2’-OH, which is a highly reactive group, makes RNA labile and easily degradable than DNA.

QUESTION: 45

A DNA segment has a total of 1000 nucleotides, out of which 240 of them are adenine containing nucleotides. How many pyrimidine bases this DNA segment possesses?

Solution:

As per Meselson and Stahl's experiment, parent DNA was first isolated from E. coli grown in heavy 15N medium. It was then put in light 14N medium. Since, DNA shows semi conservative nature, hence, in sixth generation, the ratio of 15N/15N:15N/14N:14N/14N will be 0:1:31

QUESTION: 46

The figure below shows a stage of embryo development in a dicot plan. ‘A’ store food for growth of embryo of the seed. Identify ‘A’

Solution:

Two important RNA processing events lead to specialized end sequences in most human mRNAs: Capping at the 5’ end, and polyadenylation at the 3’ end. At the 5’ end the most distinctive specialized end nucleotide, mGppp is added and a sequence of about 200 poly A is added to the 3’ end.

QUESTION: 47

Which human chromosome has the maximum number of genes?

Solution:

Minisatellites are short non-coding repetitive sequence forming large portion of eukaryotic genome.

QUESTION: 48

A small stretch of DNA strand that codes for a polypeptide is shown below :
3' ..........CAT CAT AGA TGA AAC ........... 5'
Which type of mutation could have occurred in each type resulting in the following mistakes during replication of the above original sequence?
3`… … … …CAT CAT AGA TGA ATC… … …5`
(i) Point mutation
(ii) Single base substitution
(iii) Single base deletion

Solution:

Children from lane 1 and 3 belonged to the parents.

QUESTION: 49

Case-I

To answer the questions, study the paragraph given below:
The lac operon consists of a regulation gene and three structural gene. The lactose acts as inducer. In the presence of an Inducer such as lactose, the repressor is in inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds.  The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

Q.When the process of Lac operon is blocked by a repressor it represents:

Solution:

The lac operon regulation can be in both negative and positive ways. It is a negative control system because expression is typically blocked by an active repressor (the lac repressor) that turns off transcription and when CAP (catabolite gene activating protein) binds upstream of this operator region near the promoter and transcription increases, this is an example of a positive system.

QUESTION: 50

Case-I

To answer the questions, study the paragraph given below:
The lac operon consists of a regulation gene and three structural gene. The lactose acts as inducer. In the presence of an Inducer such as lactose, the repressor is in inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds.  The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

Q. Identify the correct sequence of the structural genes in the lac operon.

Solution:

The lac operon consists of 3 structural genes, and a promoter, a terminator, regulator, and an operator. The three structural genes are: lacZ, lacY, and lacA.

QUESTION: 51

Case-I

To answer the questions, study the paragraph given below:
The lac operon consists of a regulation gene and three structural gene. The lactose acts as inducer. In the presence of an Inducer such as lactose, the repressor is in inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds.  The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

Q. Which of the following statement is true in reference to the lac operon process in E.coli?
(i) Galactosidase is the only enzyme produced in large quantities when lac operon is turned on
(ii) The messenger RNA in lac operon is a polycistronic mRNA

Solution:

The messenger RNA produced by transcription carries information for the synthesis of all three proteins found in all three structural genes. Hence, it is a polycistronic messenger RNA.

QUESTION: 52

Case-I

To answer the questions, study the paragraph given below:
The lac operon consists of a regulation gene and three structural gene. The lactose acts as inducer. In the presence of an Inducer such as lactose, the repressor is in inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds.  The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

Q. What provides binding site to RNA polymerase?

Solution:

Promoter helps in starting the process of transcription and provides a binding site to RNA polymerase.

QUESTION: 53

Case-I

To answer the questions, study the paragraph given below:
The lac operon consists of a regulation gene and three structural gene. The lactose acts as inducer. In the presence of an Inducer such as lactose, the repressor is in inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds.  The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

Q. The lac operon of E. coli contains genes involved in lactose metabolism. It's expressed only when lactose is____________(1) and glucose is _________(2).

Solution:

The lac operon of E. coli contains genes involved in lactose metabolism. It's expressed only when lactose is present and glucose is absent.

QUESTION: 54

Case-I

To answer the questions, study the paragraph given below:
The lac operon consists of a regulation gene and three structural gene. The lactose acts as inducer. In the presence of an Inducer such as lactose, the repressor is in inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds.  The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.

Q. Which of the following conditions are crucial to maintain high activation of the lac operon?

Solution:

Large concentrations of cAMP and large concentrations of lactose maintain high activation of the lac operon.

QUESTION: 55

What is the pattern of inheritance in the given below pedigree chart?

Solution:

The pattern of inheritance in the pedigree chart is autosomal linked recessive trait as it is transmitted from parents to offspring when both partners are carrier for the gene or heterozygous.

QUESTION: 56

The following is the illustration of the sequence of ovarian events “a” to “i” in a human female.
Identify the figure that illustrates corpus luteum.

Solution:

‘g’  illustrates corpus luteum. It produces the hormone progesterone causes proliferation of the endometrium which gets highly vascularised. It is essential for the implantation of the fertilized ovum and to maintain the same during pregnancy.

QUESTION: 57

In a given figure sterilisation procedure has been shown. Identify the procedure and ‘X’ .​

Solution:

Sterilisation procedure in the male is called ‘vasectomy while that in the female is called tubectomy”.
In vasectomy, a small part of the vas deferens is removed or tied up through a small incision on the scrotum where as in tubectomy, a small part of the fallopian tube is removed or tied up through a small incision in the abdomen or through vagina.

QUESTION: 58

Identify the labelled structure shown in the diagram that receives pollen during pollination

Solution:

Stigma – The head of the pistil. The stigma receives pollen, which will begin the process of fertilization.

QUESTION: 59

The below diagram shows a part of the human female reproductive system. 

Name the gamete cells that would be present in ‘X’ if taken from a newborn baby.

Solution:

The gamete present in 'X', i.e., ovary if taken from a new born baby is primary oocytes.

QUESTION: 60

Study the Punnet Square graph given below. In a cross between two tall  pea plants, some of the offsprings produced were dwarf.​
W
Which one of the following conclusions it indicates?

Solution:

In a cross between two tall pea plants, some of the offspring produced were dwarf. It indicates that parent pea plants were heterozygous for tallness (Tt) i.e., they contain a recessive gene (t) for dwarfness from each of the parent plant.

Use Code STAYHOME200 and get INR 200 additional OFF
Use Coupon Code