hnRNA undergoes splicing to remove introns and join exons.Splicing occurs in the nucleus of the cell.

Enzyme involved in continuous replication of DNA strand is DNA-dependent DNA polymerase. Template strand has 3'⟶ 5' polarity.

Between the two amino acids (found on charged tRNA), bound to the two sites of the large sub units of bacterial ribosomes, when two 2harged tRNAs are brought close enough, peptide bond is formed with the help of ribozyme.

(i) Blending is the mixing of two colours,but in this example red and white colours are appearing independently at cellular level. Thus, no blending of characters occurs in this case. Also, red and white colours reappear in F₂ - generation.
(ii) This phenomenon is known as incomplete dominance.

Advantages of using Drosophila as genetic material
Drosophila is a very useful organism for genetical experiments because:
(i) Very large number of offsprings are produced after each mating.
(ii) It can be cultured in large number in laboratory and animals can be easily examined under a handlens
(iii) Its life cycle is very short and is completed in 10-12 days. A new generation can be obtained every two week.
(iv) It has four pairs of chromosomes all different in size and easily distinguishable.
(v) They produce numerous variants.
(vi) It has heteromorphic (XY) chromosomes in the male.
(vii) Female Drosophila files can be easily differentiated from the males by the large body size and presence of ovipositor in the abdomen.

Eyes of Octopus and those of mammals are analogous structures, which have resulted from convergent evolution.
They have not evolved from common ancestors.

 A protein acquires a charge depending on the abundance of amino acids residues that have positively charged groups in their side chains. Histones are rich in basic amino acids residues-lysines and arginine both of these amino acids carry positive charges in their side chains,.Hense, histones are positively charged molecules.

Since dwarfness (recessive trait) has appeared in the progeny, the tall pea plant must be heterozygous for tallness, i.e. its genotype is Tt

The phenotypic ratio is 3 Tall : 1 dwarf.
Since tallness is dominant over dwarfness, the homozygotes (TT) as well as the heterozygotes (Tt) are tall.
The recessive trait is expressed only under homozygous condition (tt) and hence appears only in one-fourth of the progeny.

(a)Defective gene is on X chromosome, in case the carrier female (mother) passes X^h to the son he suffers, if she passes X^h to the daughter, she has the other X (from father) to make it heterozygous so the daughters escape as carriers.
(b)The blood does not clot in the affected person after an injury or a small cut.

Initial process of transcription in bacteria:
1) The process of copying genetic information from antisense or template strand of DNA into RNA is called transcription.
2) The segment of DNA that takes part in transcription is called transcription unit, It has three components
(i) A promoter
(ii) The structural gene 
(iii) A terminator
3) Structural gene is component of that strand of DNA which has 3'->5' polarity as transcription can occur only in 5'->3' direction
4) Transcription requires a DNA-dependent RNA polymerase and initiation factor
5) Bacteria have only one type of RNA polymerase which transcribes all the three types of RNAs
6) Ribonucleotides of ribose series are activated through phosphorylation (ATP, GTP, CTP, UTP)
7) Transcription begins at initiation site. A promotor has RNA polymerase recognition site and it binds to the specific site.
8)Enzymes required for unwinding of chain are unwindase and single cell binding proteins
9) Nucleotides are added as per base pairing rule

The lac operon consists of
(i) three structural genes (z,y and a) which code for \(\beta \) -galactosidase, permease and transacetylase, respectively.
(ii) an operator; which controls the structural genes as a unit.
(iii) a regulatory gene ti.e., inhibitor gene) and
(iv) a promoter, where the RNA polymerase binds for transcription.
The regulatory gene codes for the repressor protein, all the time (constitutively): the repressor binds to the operator to inactivate the operon.
 Lactose enters the cell with the help of permease and the active form of lactose binds to the repressor and prevents it from binding to the operator.
This allows RNA polymerase an access to the promoter and transcription continues, i.e. lac operon is activated.

(a) Male heterogamety
A male grasshopper produces two types of gametes with reference to sex chromosomes, i.e. 50% of them with one X-chromosome and 50% of them with no X-chromosome.
A male Drosophila produces 50% of gametes with one X-chromosome and 50% of them with one V-chromosome.
Since they produce two types of gametes with reference to sex chromosomes, they are said to show male heterogamety.
b)Female heterogamety
It is the phenomenon in which females of a species produce two types of gametes with reference to sex-chromosomes.
It is seen in fowls, where a female has ZW sex chromosomes and produces 50% of ova with one Z-chromosomes and 50% of them with one W-chromosome.
The sex of the offspring is determined by the type of ovum fertilised.

1.The gene for haemophilia is present on the X chromosome, i.e. sex-linked.
2.The disorder is due to a recessive mutant allele; hence a female with XX sex chromosomes, must be homozygous to produce the disease.
3.She must receive one of the defective alleles from her haemophilic father and the other X-chromosome with the defective allele from her mother; who is also haemophilic or at least a carrier (heterozygous for the trait, XXh).
4.The cross is as follows.

Kinds of selections:
1. Stabilising selection
2. Directional selection
3. Disruptive selection.

(i) In translation, a particular amino acid becomes activated and attached to the 3' end of a specific tRNA molecule.
(ii) The reaction is catalysed by the enzyme amino-acyl-tRNA synthetase.
\(Amino\quad acid\left( AA \right) +ATP\xrightarrow { Enzyme } AA-AMP-Enz+{ PP }_{ i }\\ AA-AMP-Enz+tRNA\longrightarrow AA-tRNA+AMP+{ PP }_{ i }\)
(iii) Initiation of protein synthesis
(iv) The ribosome, in its inactive state exits as two subunits - a large subunit and a small subunit.
(v) When the small subunit encounters the mRNA, translation begins.
(vi) The mRNA binds to the small subunit of ribosome, following base pair rule, between the bases of mRNA and those on rRNA; it is catalysed by certain 'initiation factors'.
(vii) There are two sites on the larger subunit, the P-site and the A-site.
(viii) The small subunit (with the tRNA) attaches to the large subunit in such. a way that the initiation codon (AUG) comes on the P-site.
The initiator tRNA (methionyl tRNA) binds to the P-site.
(ix) Elongation of polypeptide chain
 (x) A second tRNA charged with an appropriate amino acid binds to the A-site of the ribosome.
(xi) A peptide bond is formed between the carboxyl group of methionine and the amino group of the second amino acid; this reaction is catalysed by the enzyme peptidyl transferase.
(xii) The ribosome moves from one codon to the next along the mRNA in the \({ 5 }^{ ' }\longrightarrow { 3 }^{ ' }\) direction.
(xiii) Amino acids are added 'one by one in the sequence of the codons and become joined together.
Termination of polypeptide synthesis
(i) When one of the termination codons (UAA, UAG, UGA) comes at the A-site, it does not code for any amino acid and there is no tRNA molecule for it.
(ii)  As a result, the polypeptide synthesis (or elongation of polypeptide) stops.
The polypeptide synthesised is released from the ribosome, catalysed by a 'release factor'.