Two essential roles played by ribosomes during translation are:
(i) One of the ribosomal RNA (rRNA, 23S in prokaryotes)acts as a transferase ribozyme for the formation of peptide bonds.
(ii) The mRNA and changed tRNAs are attached to ribosomal sites.Thus, these provide sites for the attachment during protein synthesis.

It is a sudden, stable, inheritable alteration in the sequence of a gene capable of changeing the phenotype of an organism. 

Morgan's Concept of Linkage
Morgan (1910) while working on Drosophila concluded from his experiments and defined linkage as:
The tendency of genes present on the same chromosome to remain in their original combination and enter together in the same gamete."
Salient features of the theory of Linkage
1. Genes are arranged in a linear fashion on the chromosome.
2. Genes that show linkage are present on the same chromosome.
3. Linked genes remain in their original combination during course of inheritance.
4. The genes which are closely located show strong linkage while those widely separated have more chances of separation during crossing over.

(i)Bacteria
(ii)Yeast
(iii)Caenorhabditis
(iv)Drosophila
(v)Rice
(vi)Arabidopsis

Both the strands of DNA are not copied during transcription for the following reasons:
(i) If both the strands of DNA are copied, two different RNAs (complementary to each other) and hence two different polypeptides would be formed; if a segment of DNA produces two polypeptides, the genetic information machinery becomes complicated.
(ii) The two complementary RNA molecules (produced simultaneously) would form a double-stranded RNA rather than getting translated into polypetides.
(iii) RNA polymerase carries out polymerisation in the 5' ~ 3' direction and hence the DNA strand with 3' ~ 5' polarity acts as the template strand.

It is a stop/termination codon

UAA or UAG

They terminate the translation process i.e they stop the elongation of the polypeptide chain during translation.

(b) Satellite DNA is separated from the genomic DNA by density gradient centrifugation; the satellite DNA forms smaller peaks, while the genomic DNA forms a major peak.
(c) (i) They form very useful tools in identification of criminals.
(ii) It is the basis of paternity testing, in case of disputes.

(i) Transcription unit in a bacterium consists of a promoter, structural genes, terminator and the enzyme DNA-dependent RNA-Polymerase.
(ii) In bacteria, there is a single RNA polymerase, which catalyses transcription of all the three types ofRNAs (mRNA, tRNA and rRNA)
(iii) It binds transiently with the initiation factor (sigma factor), binds to the promoter and initiates transcription.
(iv) It also facilitates opening of the double helical DNA and only the DNA strand with 3'⇢ 5' polarity is transcribed, as the enzyme can polymerise the nucleotides only in 5' ⇢ 3' direction; it catalyses elongation using the ribonucleotides. 
(v) Once the polymerase reaches the terminator sequence, it associates with the termination factor and the nascent RNA falls off and termination of transcription occurs.

(a) Francis Crick
b) Clover leaf / inverted L,
Anticodon loop (complementary to codon of mRNA), acceptor end (to bind amino acid).
It reads the codons on rnRNA with the help of anticodon loop, brings the corresponding amino acid for the formation of polypeptide chain.

(a)Father = l^Ai
Child=ii
Father = l^Ai                X             I^Bi        

Phenotypes of all off springs = AB, B, A and 0 blood group
(b) Genetic basis of blood group
Three alleles of one gene/multiple alleles/gene l^A, I^B,l
A and B are co-dominant /expressed together
 

1. Law of segregation states that the members of the allelic pair that remained together in the parent/hybrid, segregate during gamete formation and enter different gametes.
2.As a result, gametes have only one allele for a trait and are pure for a character,
Parents                : Tall plant  X Dwarf plant 


3. Tall plants: Dwarf plants
3                    1
4. In this case, tallness is dominant and dwarfness is recessive.
5. The \(F_{ 1 }\)  hybrid is tall (dominant character).
6. The recessive character, dwarfness, remains hidden in the \(F_{ 1 }\)  but reappeared in the \(F_{ 2 }\)  generation without any change.
7. This' is because the factors T and t remained together in the hybrid, but segregated during gamete formation and entered different gametes.
 Diploid condition is restored during fertilisation.

(a) It is due to trisomy of 21st chromosome.
The symptoms include
Short stature and small round head with a flat back.
Rartially open mouth with furrowed tongue.
Broad, flat face with slanting eyes.
Broad palm with characteristic palm crease.
Retarded physical, mental and psychomotor development.
It is caused by the non-segregation of the 21st chromosomes during meiosis in the gamete formation; when such an ovum is fertilised by a normal sperm, the individual comes to possess three copies (trisomy) of 21st chromosome.
(b)

The RNA molecule given in question should be

As RNA have uracil in the place of thymíne, for given RNA, the transcription unit will be

Transcription is catalysed by 'DNA-dependent RNA polymerase

(i) Glycosidic bond (C-N-C)
(ii) Phospho-ester bond
(iii) Phospho-diester bond
(iv) Hydrogen bond [Double hydrogen bond between A & T (A=T) & Triple hydrogen gas bond between C & G (C\(\equiv \)G)]

(1) RNA polymerase II
(ii) Has (non-functional) introns
(Methyl guanosine tri-phosphate is added to 5' end) capping, tailing (Poly A tail at 3' end added), splicing (introns are removed and exons are joined).

The genotypes of parents must be Hb^A Hb^S and Hb^A Hb^S .

A large number of insects show XO type of sex determination while some of the sperms bear an X chromosome and others do not have an X chromosome; X chromosome become female and those fertilized by sperms that lacks X chromosome becomes male.Rest of the chromosome are named autosomes.In Drosophila melanogaslar and human being, the males have XY chromosomes & females have XX chromosomes.

It constitutes 15% of total RNA and is smallest out of three with only 70-85 nucleotides having sedimentation coefficient 45. It is of 100 types. Nitrogen bases of some nucleotides are modified to provide coiling to the otherwise single stranded RNA. The tRNA has two models clover leaf and L-form model. It has different specific loops as shown:

(a) Genotype of the parents in generation I:
 Male (Father) - Aa'
 Female (Mother) - Aa Son (Generation II) - Aa Daughter (Generation II) - aa
(b) Genotype of the daughters in generation III - Aa
(c) It is an autosomal trait, because if the sex-linked trait has to appear in the daughter (generation II), the father must have it; but he does not show the trait and so it is not sex-linked.

(a) Offspring 1 may have blood groUP
\(A(I^{ \wedge }i)\)or blood group \(B(I^{ \wedge }i)\)
(b) Offspring 2 may have blood group
\(A(I^{ \wedge }i)\)  or blood group 0 
Offspring 3 may have: If offspring 1is of blood group A
=> blood group A (may be \(A(I^{ \wedge }i)\)  or \(A(I^{ \wedge }i)\)
=> blood group o(ii), if father is heterozygous for A If offspring 1 is of blood group B
=> blood group AB (IAIB)
=> blood group A \(A(I^{ \wedge }i)\)
=> blood group B \(B(I^{ \wedge }i)\) ,if father is heterozygous for A
=> blood group 0 (ii), if father is heterozygous for A

(i) (b) : X is a communicable disease that is transmitted through vectors. It could be malaria, chikungunya, etc. Y is communicable disease that is transmitted through droplet infection. It could be rhinitis, diphtheria, pertussis, etc.
W is a non-communicable disease like diabetes that is caused by deficiency of insulin hormone. Z is a non-communicable degenerative disease like Alzheimer's disease.
(ii) (c) : Sleeping sickness is caused by Trypanosoma. Diphtheria is caused by Corynebacterium diphtheriae. In myocardial infarction a large portion of heart muscle is deprived of blood due to coronary thrombosis and patient develops heart attack.
(iii) (b)
(iv) (a) : Leprosy is a bacterial infection that spreads through prolonged contact with the infected person. Whooping cough spreads through droplet infection. Botulism spreads through faecal oral route.
(v) (b)

(a) Cannabinoids and cocaine/coca alkaloids.
(b) (i) Cannabinoids are obtained from Cannabis sativa.
(ii) Cocaine is obtained from Erythroxylum coca.
(c) Atropa bel/adona and Datura show hallucinogenic properties.

(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
Explanation:
In the ABO system, consists four blood groups A, B, AB and O. ABO blood groups are controlled by gene I. The gene has three alleles I^A, I^B and i. This phenomenon is known as multiple allelism. IA and IB are completely dominant over i. When I^A and I^B are present together, they both express themselves and produce AB blood group. This phenomenon is known as codominance.

d) If A is false, but R is true

(a) Both A and R are true and R is the correct explanation of A.
The backbone of a DNA strand is built up of alternate deoxyribose sugar and phosphate group. The phosphate group is connected to carbon 5 of the sugar residue of its own nucleotide and carbon 3 of the sugar residue of the next nucleotide by 3' \(\rightarrow\) 5' phosphodiester bonds. The two DNA chains are antiparallel, i.e. they run in opposite direction. In one chain, the direction is 5' \(\rightarrow\) 3', while in the opposite one, it is 3' \(\rightarrow\) 5'.

(a) : Haplodiploidy is a type of sex determination in which the male is haploid while the female is diploid. It occur in some insects like bees, ants and wasps. Male insects are haploid because they develop parthenogenetically from unfertilised eggs. Meiosis does not occur from fertilised eggs and hence diploid.