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61, 3

Detailed answer:

There are on the whole 64 codons which are of triplet nature. Out of which 61 codons code for amino acids and 3 codons (UAA, UGA & UAG ) do not code for any amino acid. They act as stop codons or terminating codons.

The features of genetic code are : 

(a) Stop codon : does not code for any amino acid / terminates the synthesis of polypeptide chain. 

(b) Unambiguous codon : one codon codes for one amino acid only. 

(c) Degenerate codon : some amino acid are coded by more than one codon. 

(d) Universal codon : genetic code is same for all organisms (bacteria to humans).

Detailed Answer:

The features of genetic codes are:

(a) Stop codon : Termination codons or stop codons are UAA, UAG and UGA. They do not code for any amino acids They represent termination of translation. 

(b) Unambiguous codon : The genetic code is specific and non-ambiguous i.e. one codon specifies only one amino acid. 

(c) Degenerate codon : This indicates that a single amino acid is represented by many codons. 

(d) Universal codon : This indicates that one codon codes for the same amino acid in all species. From bacteria to human, UUU codes for phenyl alanine.

The organisms which are restricted to a narrow range of temperature are called stenothermals.

Eurythermals are organisms that can tolerate and thrive in a wide range of temperature, whereas stenohalines can tolerate a narrow range of salinities.

Eurythermals show a wide range of distribution on earth, as they show tolerance for wide range of temperatures.

1. 2968 instead of 1968 

2. No change

1. act as cap. In capping an unusual nucleotide (methyl guanosine triphosphate) is added to the 5′- end of hnRNA. 

2. Joints DNA fragments during replication

physical mutation and chemical mutation

(i) isolation of DNA 

(ii) digestion of DNA by restriction endonucleases 

(iii) separation of DNA fragments by electrophoresis 

(iv) transferring (blotting) of separated DNA fragments to synthetic membranes, such as nitrocellulose or nylon 

(v) hybridisation using labelled VNTR probe 

(vi) detection of hybridised DNA fragments by autoradiography

Chasmogamous  flowers have exposed anthers and stigma. Cross pollination cannot occur in cleistogamous flowers, as such flowers do not open at all.

Watson and Crick had proposed the semi-conservative scheme for replication of DNA. 

Experimental proof for semi-conservative mode of DNA replication 

• Matthew Meselson and Franklin Stahl in 1958 performed experiments on E. coli to prove that DNA replication is semi-conservative. 

• They grew E. coli in a medium containing ¹⁵NH₄Cl (in which ¹⁵N is the heavy isotope of nitrogen) for many generations. 

• As a result, ¹⁵N got incorporated into newly synthesised DNA. 

• This heavy DNA can be differentiated from normal DNA by centrifugation in caesium chloride (CsCl) density gradient. 

• Then they transferred the cells into a medium with normal ¹⁴NH₄Cl and took the samples at various definite time intervals as the cells multiplied. 

• The extracted DNAs were centrifuged and measured to get their densities. 

• The DNA extracted from the culture after one generation of transfer from the ¹⁵N medium to ¹⁴N medium (i.e., after 20 minutes; E. coli divides every 20 minutes) showed an intermediate hybrid density. 

• The DNA extracted from culture after two generations (i.e., after 40 minutes) showed equal amounts of light DNA and hybrid DNA. 

• Similar experiment was performed by Taylor and colleagues in 1958, on Vicia faba to prove that the DNA in chromosome also replicate semi-conservatively.

Watson and Crick in 1953 proposed a scheme that DNA replication was semiconservative. According to the scheme, the two parental strands separate and each strand acts as a template for synthesising a complementary strand over it. After completion of replication, each DNA had one parental strand and one newly synthesised strand. 

Experimental Proof for semi-conservative mode of DNA replication: 

• Matthew Meselson and Franklin Stahl in 1958 performed experiments on E. coli to prove that DNA replication is semi-conservative. 

• They grew E. coli in a medium containing ₁₅NH₄Cl (in which ₁₅N is the heavy isotope of nitrogen) for many generations. 

• As a result, ₁₅N got incorporated into newly synthesised DNA. 

• This heavy DNA can be differentiated from normal DNA by centrifugation in caesium chloride (CsCl) density gradient. 

• Then they transferred the cells into a medium with normal ¹⁴NH₄Cl and took the samples at various definite time intervals as the cells multiplied. 

• The extracted DNAs were centrifuged and measured to get their densities. 

• The DNA extracted from the culture after one generation of transfer from the ¹⁵N medium to ¹⁴N medium (i.e., after 20 minutes; E. coli divides every 20 minutes) showed an intermediate hybrid density. 

• The DNA extracted from culture after two generations (i.e., after 40 minutes) showed equal amounts of light DNA and hybrid DNA. 

• Similar experiment was performed by Taylor and colleagues in 1958, on Vicia faba to prove that the DNA in chromosome also replicate semi-conservatively.

Name of the test is DNA finger printing. The procedure is 

1. Isolation of DNA.

2. DNA is cut using restriction endonuclease.

3. Separation of DNA fragments by electrophoresis.

4. Blotting of separated DNA fragments on nitrocellulose.

5. hybridization using VNTR probe

6. Detection of hybridised DNA fragments by autoradiography.

DNA finger printing is used to solve the paternity dispute. DNA fingerprinting involves identifying differences in some specific regions in DNA sequence called as repetitive DNA, because in these sequences, a small stretch of DNA is repeated many times. These repetitive DNA are separated from bulk genomic DNA as different peaks during density gradient centrifugation.

• The bulk DNA forms a major peak and the other small peaks are referred to as satellite DNA. Depending on base composition (A : T rich or G : C rich), length of segment, and number of repetitive units, the satellite DNA

• DNA is classified into many categories, such as micro-satellites, mini-satellites etc. These sequences normally do not code for any proteins, but they form a large portion of human genome.

• These sequence show high degree of polymorphism and form the basis of DNA fingerprinting. Since DNA from every tissue (such as blood, hair- follicle, skin, bone, saliva, sperm etc.), from an individual show the same degree of polymorphism, they become very useful identification tool in forensic applications. Further, as the polymorphisms are inheritable from parents to children, DNA fingerprinting is the basis of paternity testing, in case of disputes. 

• The technique of DNA fingerprinting was initially developed by Alec Jeffreys. Lalji Singh is called father of Indian DNA fingerprinting or DNA profiling or DNA typing. He used a satellite DNA as probe that shows very high degree of polymorphism. It was called as Variable Number of Tandem Repeats (VNTR).

• The technique, as used earlier, involved Southern blot hybridisation using radiolabelled VNTR as a probe. It included 

(i)  Isolation of DNA,

(ii)  Digestion of DNA by restriction endonucleases,

(iii)  Separation of DNA fragments by electrophoresis,

(iv)  Transferring (blotting) of separated DNA fragments to synthetic membranes, such as nitrocellulose or nylon,

(v)  Hybridisation using labelled VNTR probe, and

(vi)  Detectionof hybridised DNA fragments by autoradiography.

• Variable number of tandem repeats belong to the class of satellite DNA referred to as mini satellite. 
• The number of repeats shows very high degree of polymorphism as a result the size of VNTR varies. 
• After hybridisation of DNA sample with VNTR probe, an autoradiogram developed which gives many bands give the characteristic pattern of an individual DNA.

DNA fingerprinting. DNA fingerprinting involves identifying differences in some specific regions in DNA sequence

1. Genetic code is unambiguous and specific: A codon always species the same amino acid, it cannot code for more than one amino acid.

2. Genetic code is degenerate: Some amino acids are coded by more than one codon.

3. Genetic code is universal: Each codon of it species or codes for the same kind of amino acid in all organisms. (Eg. UUU-phenyl alanine).

4. Genetic code is polarised: In specifying a particular polypeptide, the genetic code has a definite initiation codon and a terminal codon.

1. A small stretch of DNA repeated many times is called repetitive DNA.

2. Variable Number of Tandem Repeats

3. Polymerase chain reaction – Synthesis of multiple copies of DNA of interest.

1. C may be the true father.

2. As the bands presented is the finger print match between child and person C. It denotes that hereditary materials are more or less common in these two bands. Usually a child comes 50% of hereditary materials from his father. So ‘C’ may be the father of the child.

3. Principle behind it is VNTRs. Southern blotting using variable number of Tandem Repeats (VNTR) as a probe.

(a) Paternity is confirmed

VNTR bands / finger print bands / bands are similar.

(b) Steps of DNA finger printing techniques are 

(i) Isolation of DNA 

(ii) Digestion of DNA by restriction endo nuclease 

(iii) Seperation of DNA fragment by Electrophoresis, 

(iv) Plotting of DNA fragment into Nitro cellulose 

(v) Ditection of hybridised DNA by Auto radiography

A. Digestion of DNA by restriction endonuclease

B. Blotting of separated DNA fragments to synthetic membranes (nitrocellulose)

C. Hybridisation using VNTR probe.

(i) Artificial hybridization is done for obtaining the improved quality of fruits and crops. 

(ii) The baggrng of the flowers is done to avoid the pollination by unwanted pollen grains present in air and also that only the pollen with desired traits may be used to pollinate the covered flowers manually. 

(iii) The caretaker has exhibited the scientific aptitude, awareness and knowledge. Mohan and his friend have shown a high value and ability of keen observation  and inquisitiveness.

The transfer of pollen grains from the anther to the stigma of another flower of the same plant is called geitonogamy. 

Although geitonogamy is functionally cross pollination involving a pollinating agent, genetically it is similar to autogamy since the pollen grains come from the same Plant.

 (1)  Pollens release and stigma receptivity is not synchronised. 

(2) Anther and stigma are placed at different positions so that the pollen cannot come in contact with the stigma on the same flower. 

(3) Self-incompatibility. 

(4) Production of unisexual flower.

ZZ type is seen in birds. The males are homogametic (ZZ) and females are heterogametic (ZY). Sex is determined by the type of egg getting fertilised. 

XY type is seen in human beings The males are heterogametic (XY) and females homogametic (XX). Sex is determined by the type of sperm fertilising the ovum.

XX-XY type (Lygaeus Type) sex determination is seen in Drosophila. The females are homogametic with XX chromosome, while the males are heterogametic with X and Y chromosome. Homogametic females produce only one kind of egg, each with one X chromosome, while the heterogametic males produce two kinds of sperms some with X chromosome and some with Y chromosome.

The sex of the embryo depends on the fertilizing sperm. An egg fertilized by an ‘X’ bearing sperm produces a female, if fertilized by a ‘Y’ bearing sperm, a male is produced.

In grasshopper, the mechanism of sex determination is of the XO type. In females, the eggs bear a pair of X chromosomes along with the autosomes. On the other hand, there are two types of sperms formed in males–one having a X chromosome and other without X chromosome. Hence, grasshopper shows male heterogamety.

1. If there is a blockage in the fallopian tubes due to which fertilization is prevented, then ZIFT treatment is used. 

2. The oocyte is removed form woman’s ovary. This oocyte is fertilized outside the body under sterile conditions with the known sperms. This forms zygote. This is In Vitro Fertilization (IVF). 

3. Later the zygote is transferred in fallopian tube to achieve pregnancy.

Coronary arteries.

1. Transport of respiratory gases (Oxygen and CO ). 

2. Transport of digested food materials to the different body cells. 

3. Transport of hormones. 

4. Transport of nitrogenous excretory products like ammonia, urea and uric acid. 

5. It is involved in protection of the body and defense against diseases. 

6. It acts as buffer and also helps in regulation of pH and body temperature. 

7. It maintains proper water balance in the body.

• All arteries carry oxygenated blood, except pulmonary arteries, which carry deoxygenated blood from the right ventricle to the lungs.
• All veins carry deoxygenated blood, except pulmonary veins, which carry oxygenated blood from the lungs and to the left atrium of the Heart.

Aortic valve present at the base of aorta.

1. (a) If both A and R are true and R is correct explanation of A.

2. (a) If both A and R are true and R is correct explanation of A.

The process is imbibition’. The type of diffusion in which a solid absorbs water and gets swelled up is Imbibition.

No. Arun is not correct. It is called as Analogous organ. They look similar and perform similar functions, but they have different origin and developmental pattern.

A stethoscope is an instrument used to detect the sound produced by the internal organs of human body. It is an useful diagnostic tool to identify and localize health problems and diagnose disease.

The walls of the left ventricle are about three times thicker than the right ventricle. The left ventricle gives rise to the aorta, which carries oxygenated blood, to various organs of the body. The ventricle walls are thick because they have to pump out blood with force away from the heart.

The age of fossils is determined by radioactive elements present in it. The elements may be carbon, uranium, lead or potassium. Carbon consumption of animals and plants stops after death, and the decaying process of C14 occurs continuously. The time passed since the death of a plant or animal can be calculated by measuring the amount of C14 present in their body.

1. True 

2. False – Right half of heart receives and pumps off deoxygenated blood. 

3. False – Between right auricle and right ventricle seen tricuspid valve. 

4. True 

5. False – By active transport sucrose moves into the cells where it is utilised or stored.

A. (iv) 

B. (iii)

C. (i) 

D. (ii)

1. systole 

2. pulmonary vein 

3. blood pressure 

4. myogenic 

5. sino atrial node 

6. 120 

7. deoxygenated 

8. William Harvey 

9. Pulmonary artery

10. 72 

11. Haemoglobin 

12. upward 

13. xylem 

14. active absorption 

15. phloem

No, we cannot group these animals together because development of eye is not a point utilised in classification as well as in evolution.

The process of formation of fossil in the rocks is called Fossilization. The common methods of fossilization include:

1. Petrifaction: Minerals like silica slowly penetrate in and replace the original organic tissue and forms a rock-like fossil. This method of fossilization can preserve hard and soft parts mostly bones and wood fossils are petrified.

2. Mould and cast: A replica of a plant or animal is preserved in sedimentary rocks. When the organism gets buried in sediment it is dissolved by underground water leaving a hollow depression called a mould. It shows the original shape but does not reveal the internal structure. Minerals or sediment fill the hollow depression and form a cast.

3. Preservation: Original remains can be preserved in ice or amber (tree sap). They protect the organisms from decay. The entire plant or animal is preserved.

4. Compression: When an organism dies, the hard parts of their bodies settle at the bottom of the sea bed and are covered by sediment. The process of sedimentation goes on continuously and fossils are formed.

5. Infiltration or Replacement: The precipitation of minerals takes place which later on infiltrates the cell wall. The process is brought about by several mineral elements such as silica, calcium carbonate and magnesium carbonate. Hard parts are dissolved and replaced by these minerals.

Survival of the fittest or Natural selection : During the struggle for existence, the organisms which can overcome the challenging situation, survive and adapt to the surrounding environment. Organisms which are unable to face the challenges, are unfit to survive and disappear. The process of selection of organisms with favourable variation is called as natural selection.

Light reaction use light to synthesize ATP and NADPH₂ . The calvin cycle uses these reactants to produce sugar from CO₂ molecule.

This cycle then produce NAP + ADP + Pi which is used in light reaction with H₂O molecules to produce ATP and NADPH₂ again.

Fossils provide solid evidence that organisms from the past are not the same as those found today. Fossils show a progression of evolution by comparing the anatomical record of fossils with modem and extinct species. Palaeontologist can infer the linkages of their species. For this the body parts such as shell bones or teeth are used. The resulting fossil record tells the story of the part and show the evolution of form over millions of years.

Sachs classified tissue system in plants into three types.

• Photosynthesis
• Storage of starch
• Synthesis of fatty acids
• Storage of lipids
• Formation of chloroplasts

1. False – Phloem tissue is involved in the transport of food in plants. 

2. True 

3. False – In monocot stem cambium is absent. 

4. True 

5. True 

6. False – Aerobic respiration produces more ATP than anaerobic respiration.

The air space that is found next to the stomata is called respiratory cavity or sub stomatal cavity.