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Some amino acids are coded by more than one codon (known as degeneracy of codon), hence on deducing a nucleotide sequence from an amino acid sequence, multiple nucleotide sequences will be obtained. 

For example, isoleucine has three codons AUU, AUC and AUA. Hence a dipeptide Met– Ile can have any of the following nucleotide sequences: 

i. AUG–AUU

ii. AUG–AUC

iii. AUG–AUA

If we deduce amino acid sequences of the above nucleotide sequences, all the three will code for Met–Ile.

The lac operon consists of structural genes, promoter, operator, repressor, and inducer. 

When Lactose is Absent 

i. When lactose is absent, i gene regulates and produces repressor mRNA which translate repression. 

ii. The repressor protein binds to the operator region of the operon and as a result prevents RNA polymerase to bind to the operon. 

iii. The operon is switched off. 

When Lactose is Present 

i. Lactose acts as an inducer which binds to the repressor and forms an inactive repressor. 

ii. The repressor fails to bind to the operator region. 

iii. The RNA polymerase binds to the operator and transcribes lac mRNA. 

iv. lac mRNA is polycistronic, i.e., produces all three enzymes, β-galactosidase, permease and transacetylase. 

v. The lac operon is switched on.

Albuminous seeds retain a part of endosperm as it is not completely used up during embryo development. e.g., wheat, maize, barley, castor, sunflower. 

When remnants of nucellus are persistent it is said to have a perisperm. Example; biack pepper, beat.

Development of endosperm (preceding the embryo) takes place in both, developing embryo derives nutrition from endosperm Endosperm is retained/persists /not fully consumed in castor, endosperm is consumed in groundnut.

Detailed Answer: 

Endosperm development precedes embryo development. The triploid primary endosperm nucleus (PEN) undergoes repeated mitotic divisions, without cytokinesis, at this stage of development, the endosperm is called free-nuclear endosperm wall formation takes place later on, as a result, the endosperm becomes partly or fully cellular. The cells of the endosperm store food materials, which are later used by the developing embryo.

The endosperm may be completely utilized by the developing embryo before the maturation of seeds as in pea, bean, groundnut etc. in non-albuminous or non-endospermic seeds. In albuminous or endospermic seeds, a portion of endosperm persists in the mature seeds. e.g., castor.

Example : 

Non-albuminous seed  : Pea, bean, mustard. 

Albuminous seed  :  Castor, maize, coconut.

Albuminous - (with residual) endosperm is not completely used up during embryonic development. e.g, wheat / maize / castor / sunflower. 

Non albuminous - (with out residual) endosperm is completely consumed during embryonic development. e.g., pea / groundnut.

Use of ¹⁵N will be inappropriate because method of detection of ³⁵P and ¹⁵N is different (³²P being a radioactive isotope while ¹⁵N is not radioactive but is the heavier isotope of nitrogen). Even if ¹⁵N was radioactive then its presence would have been detected both inside the cell (¹⁵N incorporated as nitrogenous base in DNA) as well as in the supernatant because ¹⁵N would also get incorporated in amino group of amino acids in proteins). Hence, the use of ¹⁵N would not give any conclusive results.

As it provides nutrition for the developing embryo. It is an adaptation to provide assured nutrition to the developing embryo. Provides nutrition during and after germination.

Viruses grown in the medium containing ³²P contained radioactive DNA but not radioactive protein because DNA contains phosphorus but proteins do not contain phosphorus. Similarly, viruses grown on radioactive sulphur contained radioactive protein but not radioactive DNA because DNA does not contain sulphur.

Blood group matching, and tissue matching should be done prior to the organ transplant, the body is able to identify the'non-self' triggers the cell-mediated immune response, this rejects the graft.

Views:

The cornea can be transplanted to anyone and a  blind can see the world. HeartflungA(deny cal be transplanted and a Person is gifted -with life the mindset to volunteer to register for organ donation - (particularly eye donation). Even the live donors can donate some of their body parts e.g. kidney, liver, bone or its parts. Members of youth club should be motivated to propagate awareness in the society with regard to organ donation so that precious life in emergency may be saved.

Many states of India have banned the sale, manufacture, distribution and storage of gutka and all its variants. Gutka is banned under the provision to ban any food product containing harmful adulterants in the centrally enacted Food Safety and Regulation Act. This ban is enforced by the state Public Health Ministry, the State Food and Drug Administration and the local police. Gutka should be banned because cheating of gutka may cause a number of diseases. It may cause throat and lung cancer, discolours teeth and damages the digestive and nervous system.

(i) 

= Endothecium, 

= Middle layers, 

= Tapetum 

(ii) Tapetum provides nourishment to the developing pollen grains. The tapetal cells also secrete Ubisch granules that provide sporopollenin and other materials for exine formation.

The tumour cells are dangerous because- 

-They invade and damage the surrounding normal cells because of their rapid growth. 

- The normal surrounding cells are starved because of their competing for vital nutrients. 

- Some of the tumour cells are sloughed off and migrate to different sites of the body where they develop into new and secondary tumour by metastasis.

Cellular oncogenes or proto-oncogenes.

All humans have cellular oncogenes or proto-oncogenes, but only a few suffer from cancer because cancer only occurs on activation of oncogenes. This activation is induced by carcinogens which can be physical, chemical or biological. The chemical carcinogens present in tobacco smoke have been identified as a major cause of lung cancer.

Correct answer is

(D) both (A) and (B)

(i) Benign tumours are the masses of cells which remain confined to their original location and do not spread to other parts of the body and cause little damage.

(ii) Malignant tumours are the masses of proliferating cells called neoplastic or tumour cells. These grow very rapidly, invading and damaging the surrounding normal tissues.

(iii) Transformation of normal cells into cancerous, neoplastic cells may be induced by physical, chemical or biological agents. These agents are called carcinogens. For example X-rays, gamma rays, UV radiations and some chemicals like EtBr.

(iv) The genes which may lead to oncogenic transformations of the cells are called oncogenes.

(v) Contact inhibition—Whenever normal cells come in contact with each other, after a definite time they inhibit each other’s excess growth and multiplication. This property of normal cells is called contact inhibition which maintains the normal shape and size of the body. But cancer cells appear to have lost this property which results in their uncontrolled growth and multiplication.

Reasons for alcohol abuse in adolescents: 

i. Social pressure. 

ii. Curiosity and need for adventure, excitement and experiment. 

iii. To escape from stress, depression and frustration. 

iv. To overcome hardships of daily life. 

v. Unstable or unsupportive family structure. 

For measures to avoid taking drug are as follows: 

i. Avoid undue peer pressure. 

ii. Educating and counselling the problems and stresses to avoid disappointments and failures in life. 

iii. Seeking help from parents and peers. 

iv. Looking for danger signs to take appropriate measures on time. 

v. Seeking professional and medical help whenever required.

Correct answer is

(D) Law of purity of gametes

(A) gamete formation

The law of segregation states that when a pair of allelomorphs are brought together in the F₁ hybrid they co-exist or remain together in the hybrid without blending or in any way contaminating each other and they separate completely and remain pure during the formation of gametes.

(A) law of dominance

The character which is expressed in F₁ generation is dominant and the recessive character is suppressed in F₁ generation.

Correct answer is

(C) monohybrid cross

Correct option is (B) alleles

Correct answer is C.

In some cases, there is incomplete dominance or no dominance. Law of dominance could not support such cases. Hence, it is not universally acceptable.

(C) Four

The six genotypes are - I^AI^A or I^Ai, I^BI^B or I^Bi, I^AI^B, ii.

The four phenotypes are – A, B, AB, O.

 Correct Option is (B) multiple alleles

Innermost wall layer of microsporangium which nourishes the developing pollen grain is called Tapetum 

Correct answer is C.

Mendel’s first law is the law of dominance. Law of independent assortment is the third law. Epistasis is a drawback in Mendel’s studies, where intergenic suppression of characters is observed.

Law of segregation states that “when the two alleles for a contrasting character are brought together in a hybrid, they do not mix or contaminate but segregate or separate out from each other during gamete formation”. Law of segregation is also known as law of purity of gametes, as gametes have only one allele.

Correct Option is (B) 3 alleles in which AB is co-dominant.

 Correct Option is (B) segregation

 Correct Option is (B) Polygenic inheritance

 Correct Option is (C) independent assortment

Correct answer is

(D) independent assortment

(B) 3 : 1

Yellow round = 9

Yellow wrinkled = 3

Green round = 3

Green wrinkled = 1

From above,

i. Yellow coloured seeds = 9 + 3 = 12

Green coloured seeds = 3 + 1 = 4

∴ Yellow : Green = 12:4 = 3:1

ii. Similarly,

Round seeds = 9 + 3 = 12

Wrinkled seeds = 3 + 1 = 4

∴ Round wrinkled = 12:4 = 3:1

The triploid tissue in the ovule is the endosperm. Its triploid condition is achieved by the fusion of two polar nuclei and one nucleus of male gamete, referred to as triple fusion.

 Correct Option is (A) stresses upon slow and small variations

1. Eichornia - Lantana Camera 

2. African cat fish (clarius gariepinus) 

3. When a species becomes extinct, the species associated with it in an obligatory way also become extinct. This is called co-extinction.