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CGBSE Class 12th Biology Important Questions 2024

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CG Board Biology Important Questions 2024 – CGBSE Class 12th Biology Important Questions 2024

We will know the exam of biology is on 21 March 2024, so we will share imp questions for your preparation purposes study hard and score good marks, and also we will tell you to put extra effort into ncert books and other study materials so that you can score full marks.

5 Marks Biology Questions

Q. 1 What do you understand by gene cloning? Write the reasons for the
success.
Ans. Gene cloning : Recombinant DNA technology. This technology is also
called gene cloning or gene splicing in recombinant DNA technology. Specific
gene segments drom ore organism are transferred into the
genome of another organism using specific types of restriction endonuclease
enzymes and vectors. This technology is called recombinant DNA technology or
gene cloning.
There were three reasons for the success of this technology.
(i) Ability to DNA to undergo denaturation and renature.
(ii) Discovery of restriction endonuclease enzyme.
(iii) Development of gene linkage.
Q. 2 What is eugenics ? Write the importance of eugenics.
Ans. Eugenics: The branch of biology which deals with the study of
improvements of human race is called eugenics.
Importance :
1. lar species. isms.
2. Transfer of genetic materials in various organ3. Development of GM food and GM crops.
4. Gene cloning
5. Gene therapy, etc.
Q. 3 Explain the process of oogenesis along with a diagram.
Ans. Process of oogenesis: The process of formation of ova from oogonia in
the ovaries is called oogenesis. It consists of three phases.
(i) Multiplication phase.
(ii) Growth phase.
(iii) Maturation phase.
1. Multiplication phase : The primordial germ cells are divided by mitosis to
produce oogonia. These oogonia are divided by repeated mitotic
division forming clusters of oogonia called ovigerous cords. These lie
close to germinal epithelium. When oogonia stop dividing, they are
called oocytes.
2. Growth phase : In this phase, the oocyte increases many folds. The size
increases due to the accumulation of reserve food like protein and fats
in the form of yolk.
3. Maturation phase : In this phase, the nucleus of oocyte undergoes two
maturation divisions. The first division is meiotic, as a result two haploid
(n) cells are produced. In this division, cytokinesis is unequal, the large
daughter cell with almost entire. Cytoplasm and yolk forms the
secondary oocyte: While the smaller one with haploid nucleus (n) and
almost without cytoplasm forms the first polar body which is given off.
The secondary oocyte is haploid number of chromosome undergoes
second maturation division or second meiotic division. This division is
also unequal, the large one containing yolk is called ovum and small cell
is the second polar body.
Fig : Different phase of Oogenesis.
Q. 4 What is Spermatogenesis? Briefly describe the process of
spermatogenesis?
Ans. The development of sperms in testis is called spermatogenesis sperms
develop from germ cell present in lining epithelium of semi-niferous
tubules. The process of spermatogenesis is distinguished into two parts :
1. Formation of spermatid into sperm.
2. Metamorphosis or spermaiogenesis of spermatid
3. Formation of spermatid : Formation of spermatid is called
spermatogenesis.
It includes following phases :
(a) Phase of Multiplication : The sperm mother cell or spermatogonia is divided
repeatedly by mitosis forming new sex cells.
(b) Phase of Growth : In this phase, spermatocytes and their nuclei enlarge in
size.
(c) Phase of Maturation : Each primary spermatocyte undergoes first
maturation division which is a reductional division and two daughter cells are
formed. These daughter cells are secondary spermatocyte undergoes second
maturation division which is simple mitotic and form spermatids.
2. Formation of Spermatozoa : The transformation of spermatids into
spermatozoa is called metamorphosis. In this process, four
sperm (Spermatozoa) are formed.
Fig : Spermatogenesis
Q. 5 Explain briefly :
(i) Watson : Crick model of DNA.
(ii) Characteristics of genetic code.
Ans. Watson-Crick model of DNA : Watson and Crick, based on �-ray
diffraction method, proposed a double helical model of DNA to explain
their molecular structure for which they got Nobel Prize in 1962. The main
features of the model are as following:
Watson and Crick (1953) proposed a double helical model of DNA to explain
molecular structure.
The Model proposes :
(i) Each molecule of DNA consists of two helical polynucleotide chains or
strands. These strands run antiparallel, i.e. their ‘ 3′−5′ phosphodiester bonds
are in opposite direction and 3′ end of one strand lies besides the 5 ‘ end of the
other.
(ii) In each polynucleotide chain, the phosphate molecules lie on the outer side
of deoxyribose and the nitrogenous base, inward perpendicular to the helical
axis.
(iii) The nitrogenous bases of two strands are linked together with the help of
hydrogen bonds between oxygen and nitrogen atoms of the adjacent bases.
Since there is fixed distance between the two strands ( Å11Å or Å10.8Å ), only
specific base pairs can fit into the space. So the base pairing is very specific:
(a) Purine (adenine and guanine), two ringed nitrogenous compounds pair with
pyrimidine (cytosine and thymine).
(b) Adenine pairs with thymine and guanine pairs with cytosine. There are two
hydrogen bonds between A=T and three between G≡C. Therefore, the two
strands of the DNA molecules are complementary to each other.
(iv) In the DNA molecule, the two complementary chains are twisted around
each other and form a double helix around a common central axis.
One turn of the helix measures about Å34Å and contains 10 nucleotides
is Å3.4Å or 0.34 nm. Diameter of the helix is about Å20Å.
Fig : Watson-Crick double helical model of DNA
Fig : A part of DNA molecule showing base pairing in the two polynucleotide
chain
Q.6 What is DNA Replication ? Explain its semi-conservative method.
Ans : The structure of DNA was proposed by Waston and Crick. It is twisted
ladder like structure. It has got two coiled polynucleotides which are joined
together by nitrogen bases with hydrogen bond in the center. The longitudinal
strands of DNA are made of sugars and phosphates of nucleotides. The
horizontally placed nitrogen bases are of two types purine and pyrimidine.
Purines are adenine and guanine whereas pyrimidines are cytosine and
thymine.
During the replication of DNA, the weak hydrogen bonds between the
nitrogenous bases get separated, so that the two chains of DNA also separate
and uncoil. Each nucleotide of separated chain attracts its complementary
nucleotide from the cytoplasm. This results in the formation of two double
helixes of DNA, where in each molecule has one old strand and one
synthesized new. This method of DNA replication is known
as “semiconservative method”.
Fig. Semiconservative method of DNA Replication.
DNA Replication : The process of DNA replication involves the participation of
over an enzyme and other protein factors like :
1. DNA helicase,
2. DNA gyrase,
3. Primase,
4. DNA polymerase,
5. RNA primer,
6. DNA ligase. The process of DNA replication is complex type. The
mechanism of semiconservative replication of DNA can be studied under
following heads :
(i) DNA segment separated by DNA enzyme gyrase.
(ii) RNA primer formation by RNA polymerase enzyme and making new DNA
segment. (iii) By the help of DNA polymerase enzyme separates DNA segment
into small segment by the reaction of RNA primer. This small segment
called “Okazaki fragments”
(iv) When DNA fragment is completed DNA polymerase dissolve RNA primer.
(v) In last step the DNA ligase enzyme join the DNA fragments into new.
Fragment by phosphodiester bonds and in old DNA forming new DNA
fragments 50 DNA fragments occurs one new and old DNA fragments.
Q.7 Do you think that friends can influence one to take alcohol / drugs ? If
yes, how may one protect himself / herself from such an influence?
Ans. Undue peer pressure from friends can influence one to take alcohol /
drugs is called alcohol / drug abuses.
Measures for prevention are following :
(i) Avoid the pressure.
(ii) Educate the people to face problem.
(iii) They should seek help from their parents and teachers.
(iv) In case of adverse effects they must take the help of professional.
Q.8 Why is that once a person starts taking alcohol or drugs, it is difficult to
get rid of this habit? Discuss it with your teacher.
Ans. When a person starts using alcohol / drugs, he begins to escape from
problem. He then become addict of them. Alcohol / drug addiction increases
the tolerance level of receptors. So, receptors respond to higher doses of
alcohol or drugs. This allows much intake of alcohol / drugs.
The addictive potential of drugs / alcohol pull the person into a viscous circle
leading to abuse.
Q. 9. What is DNA recombinant technology ? describe the three steps of this
technique.
Ans. DNA recombinant technology creating a new type of DNA by inserting
genes with desired characteristics in the genome of an organism is called DNA
recombinant technology and the DNA made in this way is called recombinant
DNA. recombinant DNA technology the technique of changing the organization
of a genetic gene using DNA technology is called gene technology.
Various stages of recombinant technology
1. Selection of foreign or target DNA which has to be cloned.
2. Connecting foreign DNA with vector DNA Mean’s creation of
recombinant DNA.
3. Selection of a plasmid or lambda phage or cosmid as a vector.
4. Transfer of recombinant DNA into the host cell.
5. Selection of transformed cells:
Q 10. Explain the usage of genetic engineering in production of human
insulin.
Ans. Insulin gene from rat DNA is transferred to E. Coil with the help of
plasmid. For this insulin gene of rat and plasmid of E. Coli are isolated and
sliced with the help of restriction endon- uclease enzyme to
produce complementary ends in DNA of both the organisms. The rat DNA
and plasmid DNA segments are then joined together. It result in formation
of DNA plasmid. The recombinant DNA is added to culture medium in which
E.Coli. are growing. Host bacterium divide to produce large number of
copies of recombinant DNA.
Q. 11. Draw a labelled diagram of female reproductive system and write
function of following.
(a) Oviduct
(b) Fimbriae
Q. 12 Draw a labelled diagram of male reproductive system.
Ans. Functions : (a) Sertoli cells : Supply nutrition to the developing sperms.
(b) Leydig cells : Help in production of testosterone hormone which help in
the development of secondary sexual characters in male.
© Vas deference : Its main function is to take sperms from seminal vesicle
and then these sperms reaches to testis.
(d) Prostate gland : The primary function of prostate gland is to produce the
fluid that nourishes and transport sperm.
(e) Epididymis : The main function of epididymis is to transport sperm from
the testes to the vas deferens.
Q. 13. What is DNA finger printing ? Mention its application.
Ans. DNA finger printing is a technology of identifying individuals using
properties of their DNA.
Every person have DNA as genetic material. Many segments are repeated in
DNA of our chromosome. In DNA finger printing, DNA is separated from the
given sample or the blood spot etc. It is cut into fragments by restriction
endonuclease. Fragments are separated by electrophoresis. Through southern
blotting DNA fragments are transfered to a nylon membrane. Radioactive DNA
probes are attached to the particular parts of DNA fragments. They are
exposed on the film with light and dark bands. It is a method of ascertaining
relationship and the identify of a person by mean of DNA finger print which is
unique to each individual. DNA finger print consists of pattem of DNA fragment
obtained in restriction analysis is of some highly variable repeated DNA
fragment within the genome.
Important application of finger printing :
(i) Forensic science : DNA fingure printing is used mostly in forensic science to
identify the biological father (in case of paternity disparity) and the criminal
such as murderers and rapists etc.
(ii) In Medical science and treatment : It is used science for the bone marrow
transplantation.
(iii) It is also used to identify the racial groups to account biological evolution.
(iv) In chemical field, this technique is used in the diagnosis of pathogens.
Q14. Write the short notes about sickle and transcription?
Ans. Sickle cell anemia : This is an autosomal recessive the trait which is passed
from parents to offspring only when both parents are carrier of the gene
(heterozygous) this disease is centarell by a single pair of alleles. and . The
disease phenotype seen only in homozygous individuals with among the three
possible genotypes heterotype individuals are free from the disease but are
carriers of the disease. The couses of this disorder is the replacement glutamic
acid by valine an amino acid in the sixth position of the beta globin chain of the
hemoglobin molecule globin protein. This replacement of amino acid is due to
the replacement of GAG by GUG in the sixth codon of the beta globin gene in
low oxygen tension the mutated hemoglobin becomes shaped like a sickle.
Transcription : The process of copying genetic information from a strand of
DNA into RNA is called transcription the total DNA of an organism gets
duplicated and during transcription one of it’s strande combines with RNA
takes the same-form the transcription unit in DNA has three main parts
promoter, structural gene and terminator. The structural genes of the
transcription unit are part of the double strand of DNA. Since the strand are of
opposite polarity.
DNA dependent RNA polymerase catalyzes polymerization only in one
direction from to strand in which polarity is from to they act as a template;
hence this template is called a strand. The second larger one has polarity and
sequence RNA, A occurs (in addition to Thymine there is urecil at this position)
is transferred during transcription. This string (Which doesn’t incryption
anything) is called incryption string) All the above mentioned points which the
part of the transcription unit the coding a strands composed promoter and
terminator and structural genes located at the end from the transcription unit
the promoter is stabilized at the and of the structural gene.
This is the DNA sequence to which RNA polymerase binds and determines the
promoter tamplates and codons beta strand located in the trancription unit
the terminators is located at the end of the coding strand and determines the
end of the transcription process. A part from this there are regulators
sequence an the upstream and downstream side of the promoter.
Q. 15. Write short notes on biofertilizers.
Ans. Biofertilizers : They are defined “as organisms which can bring about soil
enrichment”.
The main sources of biofertilizers are bacteria, cyanobacteria, and fungi.
Four sources are described.
(a) Legume : Rhizobium symbiosis – It is now well known that rhizobium
produces nodules in the roots of leguminous plants and fixes atmospheric
nitrogen. Rhizobium culture raised in the laboratory are now being used for
inoculating seeds of legumes to ensure better nitrogen fixation and yields.
(b) Azolla : Anabaena symbiosis – It is now well known that it fixes nitrogen
from air and excrete nitrogenous wastes into the cavity of fern leaves.
© Loose association of nitrogen fixing bacteria : Dobreiner observed a loose
association of azospirillum lipoferum, a nitrogen fixer with the roots of certain
brazallian grass and maize in 1975.
(d) Cyanobacteria : Cyanobacteria e.g, Anabaena, Nostoc and aulosira drive the
energy needed for nitrogen fixation through photosyn thesis.
16. Write seven useful activities of bacteria.
Ans. Useful activities of bacteria :
fixation : Some bacteria play an important role in nitrogen fixation e.g.,
Azotobacter, Clostridium, Rhizobium. These bacterias Increases the fertility of
soil by the fixation of atmospheric nitrogen.
Lactic acid synthesis : Lactobacillus lacti converts the milk sugar into lactic acid.
Acetic acid synthesis : Acetobacter aceti takes part in synthesis of acetic acid or
vinegar.
Rating of fibres: Isolation of wood fibres from the stem of plants is called
rating. Clostridium butyricum is used in rating of fibres.
Tobacco and tea industry : Some bacteria like micococcus candisens is used to
increase the flavour of the leaves of tobacco and tea. This process is called as
seasoning.
Medicine production : Bacteria are the chief source of antibiotics, hence, they
are used to extract antibiotics. e.g., streptomyces gresius (Streptomycine).
As symbionts : Bacteria presents in our body, helps in the various metabolic
reactions e.g., E.coli.
Q. 17. Write the short note on :
(i) Importance of reproductive bealth in our society
(ii) Amniocentests.
Ans. (i) Reproductive health means complete physical, emotional,
behavioural and social health. India is the first country which has made
many planning at national level on reproductive bealth. That planning is
known as family welfare. It has started in
1951. Now a days, this programme at large scale are known as
reproductive and child health care. Under this programme many health
awareness programme and facilities for reproductive health are
conducted.
(ii) Amniocentesis is the prenatal diagnostic technique by which foetal
cell can be made available to examine outside mother’s body. The
developing embryo is surrounded by amniotic fluid and that fluid is taken
out in a pipette. This fluid contains some cells of foetus. This cell is
nourished, than examine to detect the sex of the foetus
during 3nd month.
Chromosomal abnormalities and genital disorders can be detected by
analysis of foetal cells.
Q 18 Short notes on :
(i) Same methods to get child for infertile couple.
(ii) Control of population growth.
Ans. (i) Some specific reproductive health technique can cure the
problem which an infertile couple can have these techniques are known
as Assisted Reproductive Technologies. (ART)
Some ART are as follows :
1. Test tube babies: Some women are unable to have a normal
conception. The process involves the removal of unfertilized egg
and then, fertilized with sperm outside the body. The zygote is
allowed to develop 32 cells stage in invitro condition and
then injected for implantation into a female body.
The embryo development takes place in female body still birth.
2. Gamete Intrafallopian transfer (GIFT) : The technique is used in
woman who are unable to produce ova but can provide suitable
environment for fertiliza tion. The ovum is surgically removed from
donor mother and inserted into fallopion tube of needed woman
and then intercourse with her husband and onum fertilize.
3. Artificial insefination : It is a technique of insemination in which
woman whose husband has low sperm count can get semen of
donor male.
4. Intra cytoplasmic sperm injection : In this technique sperm is
directly injected into ovum placed in nutrient broth.
Two methods to check the growth of population :
(ii) Control of population by planning : The most important method
to check population is to decrease birth rate. The birth rate can be
controlled by following :
(a) Education : People should be educated so that they can
understand the importance of small family.
(b) Marital age : Marital age should be increased. Legal Marital
age for Boy is 21 years and for Girls is 18 years in India.
(ii) Family planning : Following method should be adopted for Birth
control :
(a) Intercourse before one week of menstruation and after one
week of menstruation, then probability of conceiving is less.
(b) Use of Nirodh to check child birth.
© Diaphragm and cervical cap are used to prevent the entry of
sperm into uterus.
(d) Permanent surgical method – Tubectomy in female and
yasectomy in male.
Q. 19 What is protein synthesis ? Briefly write the mechanism of
protein synthesis.
Ans. A structure consisting of peptide bonds amino acids is called a
protein. Protein are responsible for the biological functions of the
organism required for editing in protein sythesis. The genetic information
of nucleic acids flows in one direction.
The process of protein synthesis is completed in two steps:
1. Transcription : The access of genetic present in DNA to RNA or
the formation of RNA by DNA is called transcription, this process
is completed in the following steps. (C.G. Board Question Bank
2024)
(i) Activation of Ribonucleotides.
(ii) Formation of DNA template.
(iii) Formation of -RNA chain with the help -DNA polymerase.
(iv) Separation of RNA.
2. Translation: The production of Proteins from mRNA is called
translation. This action is completed in the following steps:
(i) Activation of amino acides.
(ii) Addition of active amino acides to the -RNA.
(iii) The release of the polypeptide.
(iv) Increase in the length of the polypeptide chain.
(v) Termination of the polypeptide chain.
(vi) Conversion of independent polypeptide chain. Or
What is dihybridization ? Explain the law of purity of gametes by
giving the example of dihybridization. (C.G. Board Question Bank
2024)
Ans. The cross between two pairs of contrasting characters is
called dihybrid hybridization. Passing in gametes and progeny
without affecting each other is the law of purity of gametes. To
study the inheritance of two pairs of characters. Mendal crossed
the round and yellow plant with a plant with wrinkled and green
seeds and according to rule of dominance, all dominant characters
appeared in the first generation. And all the plants were bom with
round and yellow seeds but in the second generation hybridization
was done between the plants produced from seeds and two types
of bud plants were obtained.
ф RY Ry Ry ry
RRYY
Round
Yellow
RrYY
Round
Yellow
RRYy
Round
Yellow
Round
Yellow
RrYY
Round
Yellow
Wrinkled
Yellow
RrYy
Round
Yellow
Wrinkled
Yellow
Ry
RRYy
Round
Yellow
RrYy
Round
Yellow
RRyy
Round
Green
Rryy
Round
Green
ry
RrYy
Round
Yellow
Wrinkled
Yellow
Rryy
Round
Yellow
myy
Wrinkled
Yellow
Round Yellow – 9
Wrinkled Yellow – 3
Round Green – 3
Wrinkled Green -1
Phenotype
Genotype .
Q. 20. In your view, what motivates youngsters to take to alcohol or
drugs and how can this be avoided?
Ans. Motivation : The youngster at the age of puberty are vulnerable to
mental and psycho -logical development. The curiosity, excitement,
experimentation and adventure are main cause for motivation of
youngsters to take alcohol / drugs.

Natural curiosity : It motivates them to take alcohol or drugs for
experimentation but they do not get rid of it. Stress of examination may
be one reason to escape. Internet, movies, expose them to drugs and
alcohol abuse.

Prevention and control : First identify the problem to saliva. The parents
and teachers may help the alcohol/drug addict. They may take the help
of good friends, professionals and doctor also. Education and
counselling are the way to face the problems and to guide the youths
properly about addiction. Tell them the harmful effects of use of alcohol
and drugs.
Q21. Where was AIDS first found ? Mention the methods of
transmission and prevention of this disease.
Ans. AIDS (Acquired Immune Deficiency Syndrome) is discovered for
the first time in America
Causes of disease : This disease is caused by the infection of a virus
known as HIV (Human Immune Deficiency Virus).
Transmission : It is transmitted through sexual contact homosexuality,
contaminated needles, blood transfusion, drugs, artificial insemination
and organ transplantation, etc.
Symptoms of disease : It is characterized by showing swollen lymph
nodes, fever, loss of weight. The person loses the immunity against the
infection. In this disease, the number of helper T-cells are reduced.
Treatment : No suitable drug is available so far against this disease.
Only antiviral cells may be increased in the number by immune
stimulation method.
Control : The following measures are advised to prevent the spreading of
disease :
(i) Providing health education and explain the hazardous effects of AIDS.
(ii) Do not utilize the used syringe. Throw it away or destroy.
(iii) The blood of donor person and organs of transplantation like :
kidney, liver, comea of eyes, growth hormones should be carefully
examined before use.
Q. 22 What will be the inheritance of children produced by the
marriage of a normal man and a haemophilic woman ? Explain with
diagram only. Write three characteristics of Gene mutation.
Ans.
Feature of Gene Mutation :
(i) There is no three excharge in the two half chromosome of a
chromosomes.
(ii) The number of chromosomes depends on the number of paired
chromosomes.
(iii) Only two of the four half chromosomes centain the zone excharge
takes place.
Q. 23. What is gene therapy? Illustrate using the example of
adenosine deaminase deficiency.
Ans. Gene Therapy : Techniques have developed for introduction and
expression of genes in humans. These genes are delivered into human
to correct diseases and this is called gene therapy. Its main goal is gene
replacement therapy. It may be invitro or invivo.
Adenosine Deaminases Deficiency : M. Blease and W. F. Audresco
(1990) explains in humans. Four year old girlchild suffered from SCID
caused, by a faulty gene that expresses ADA. Its deficiency results
information of a chemical that destroys T and B-cells of immune system
and patient dies. A healthy ADA gene was introduced into the body of girl
by scientist that protected by immune system from damage,
Genetic disorders for gene therapy :
Disease Therapeutic
Agent Vector Target
1.
Cystic
fibrosis
2.
SCID
CFTR Adenovirus
Retroview
Nosal
epithelium
T-cells
Gene replacement therapy is of four types :
(i) Somatic gene therapy : The genetic problem of cell are cured.
(i) Gene line therapy : Gene is introduced into reproductive cells.
(iii) Enhancement genetic engineering : To correct the trait, this is used
e.g. to correct height.
(iv) Eugenic genetic engineering : It is used for personality development.
Q24. What is Transgenic Bacteria ? Explain it with a diagram and
one example.

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In this article, we focus on the important questions of class 12th biology 5 marks questions, this is very useful for the student of class 12th biology also we try to add 4 marks and 3 marks questions on our website so stay with us and check regularly the site so you get information, thank you for reading the article.