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i. George Gamow. 

ii. He proposed that there are four bases and 20 amino acids So, there should be atleast 20 different genetic codes for these 20 amino acids. The only possible combinations that would meet the requirement is combinations of 3 bases that will give 64 codons.

Euchromatin or exon.

Nucleosome Histones are organised to form a unit of eight molecules called as histone octamer. The negatively charged DNA is wrapped around the positively charged histone octamerto form a structure called Nucleosome.

Six nucleosomes get coiled and then form solenoid that looks like coiled telephone wire of 30 nm diameter (300Å).

Correct answer is A.

In Mendel’s experiments of inheritance, the progeny was systematically shown in the checker board or Punnet’s square.

Transcription in Prokaryotes 

▪ In prokaryotes, the structural gene is polycistronic and continuous. 

▪ In bacteria, the transcription of all the three types of RNA (mRNA, tRNA and rRNA) is catalysed by single DNA-dependent enzyme, called the RNA polymerase. 

▪ In E. coli bacterium, the RNA polymerase has co-factors β, β′, α, α′ and ω along with σ (sigma) factor, to catalyse the process. 

▪ The transcription is completed in three steps: initiation, elongation and termination. 

▪ Initiation: σ (sigma) factor recognises the start signal and promotor region on DNA which then along with RNA polymerase binds to the promoter to initiate transcription. 

▪ Elongation: The RNA polymerase after initiation of RNA transcription loses the σ factor but continues the polymerisation of ribonucleotides to form RNA. 

▪ Termination: Once the RNA polymerase reaches the termination region of DNA, the RNA polymerase is separated from DNA–RNA hybrid, as a result nascent RNA separates. This process is called termination which is facilitated by a termination factor ρ (rho). 

▪ In prokaryotes, mRNA does not require any processing, so both transcription and translation occur in the cytosol. It can be said that transcription and translation are coupled together.

Correct answer is (b) Radioactive ‘P’ remained in suspension.

• Procedure: 

i. Some bacteriophage virus were grown on a medium that contained radioactive phosphorus (³²P) and some in another medium with radioactive sulphur (³⁵S). 

ii. Viruses grown in the presence of radioactive phosphorus (³²P) contained radioactive DNA. 

iii. Similar viruses grown in presence of radioactive sulphur (³⁵S) contained radioactive protein. 

iv. Both the radioactive virus types were allowed to infect E. coli separately. 

v. Soon after infection, the bacterial cells were gently agitated in blender to remove viral coats from the bacteria. 

vi. The culture was also centrifuged to separate the viral particle from the bacterial cell. 

• Observations and Conclusions: 

i. Only radioactive ³²P was found to be associated with the bacterial cell, whereas radioactive ³⁵S was only found in surrounding medium and not in the bacterial cell. 

ii. This indicates that only DNA and not protein coat entered the bacterial cell. 

iii. This proves that DNA is the genetic material which is passed from virus to bacteria and not protein.

Supercoiling of solenoid fibre forms a looped structure called chromatin fibre.

The total molar amount of adenine in any specimen of DNA is always equal to that of thymine. In a given DNA A = T and G = C.

(i) Most common method of DNA replication. 

(ii) Takes place in the nucleus where the DNA is present in the chromosomes. 

(iii) Replication takes place in the S-phase (synthesis phase) of the interphase nucleus. 

(iv) Deoxyribose nucleotides needed for formation of new DNA strands are present in nucleoplasm. At the time of replication, the two strands of DNA first separate. Each strand then acts as a template for the formation of a new strand. A new strand is constructed on each old strand, and two exactly identical double stranded DNA molecules are formed. In each new DNA molecule, one strand is old (original) while the other is newly formed. Hence, Watson and Crick described this method as semi-conservative replication. 

(A) An overall process of DNA replication showing replication fork and formation of new strands template and lagging template.

NHC stands for Nonhistone Chromosomal proteins.

Frame shift mutation.

"Process by which DNA produces daughter DNA molecules which are exact copies of the original DNA." In eukaryotes, DNA is double stranded. The two strands are complementary to each other because of their base sequences.

1. AUG – Codes for methionine and it acts as initiator codon.

2. UGA – Does not code for any amino acids and acts as stop codon.

Phosphorylase, Helicase, DNA polymerase, Primase, DNA ligase, Super helix relaxing enzyme, Topoisomerase (gyrase) are different enzymes required during DNA synthesis

β – chain of haemoglobin

During replication of DNA SSBP proteins remain attached to both the separated strands and prevent them from coiling back.

Transcription occurs in the nucleus during G₁ and G₂ phases of cell cycle.

AUG – Methionine UGA – Termination codon (Nonsense codon)

DNA polymerase – I

Prokaryotes have one replicon. Several replicons in tandem are present in eukaryotes.

DNA strand having 3’ → 5’ polarity acts as template strand and it gets transcribed.

AUG and GUG.

RNA polymerase – I

Enzyme involved in synthesis of RNA primer is Primase.

DNA polymerase α

(i) 1. DNA as the genetic material has to be chemically and structurally stable.

2. It should be able to generate its replica. 

3. Sugar-phosphate backbone and complementary base pairing between the two strands, give stability to DNA. 

4. Both the strands of DNA act as template for synthesis of their complementary strands. This allows accurate replication of DNA. 

5. Single stranded RNA can be folded to form complex structures and perform specific functions such as synthesis of proteins

(ii) 1. Translation is the process in which sequence of codons of m-RNA is decoded and accordingly amino acids are added in specific sequence to form a polypeptide on ribosomes.

2. Ribosome has one binding site for mRNA. It orients m-RNA molecule in such a way that all the codons are properly read. 

3. Ribosome has three binding sites for tRNA : P-site (peptidyl t-RNA-site), Asite (aminoacyl t-RNA-site) and E-site (exit site). 

4. t-RNAs place the required amino acids in correct sequence and translate the coded message of RNA. 

5. In eukaryotes, a groove which is present between two subunits of ribosomes, protects the polypeptide chain from the action of cellular enzymes and also protects m-RNA from the action of nucleases. 

6. Thus ribosome plays an important role in translation.

(iii) The job of t-RNA is to pick up amino acids and transport them to ribosomes. t-RNA is an adapter molecule. It reads the codons of mRNA and also simultaneously transfer specific amino acid to m-RNA Ribosome complex. It binds with amino acid at its 3′ end.

(iv) In prokaryotes, translation can start before transcription is complete, as both these processes occur in the same compartment, i.e. cytoplasm. But in eukaryotes, transcription and processing of hnRNA occurs in nucleus. hnRNA then comes out of the nucleus through nuclear pores and then it is translated at ribosomes in the cytoplasm.

The strand having the polarity 3′→5′ is transcribed because RNA polymerase polymerises nucleotides only in 5′→3′ direction.

DNA polymerase

Enzyme involved in unwinding of DNA is Helicase.

The Topoisomerase

James Watson and Francis Crick in 1953.

c. These modifications facilitate pollination by Wind.

A malfunctioning tapetum does not provide enough nourishment to the developing male gametophytes and thus fail to produce viable male gametophytes.

A malfunctioning tapetum is not able to provide optimum nutrition for the production of viable male gametophytes.

1. sporopollenin

2. It is the most resistant organic material and can withstand high temperatures, strong acids, and alkali. No enzymes can degrade sporopollenin.

DNA was first isolated by Friedrich Meischer in 1869 who named it as nuclein.

Tapetum nourishes developing pollen grains

DNA and RNA.

Polymorphonuclear leukocytes, monocytes, natural killer cells and macrophages.

The B-cell specific antigens stimulate B-cell production and it multiplies to produce a clone of plasma cells. The cells differentiated into memory and effector cells due to clonal selection. They produce antibodies that circulate in body fluid and kill the pathogens.

Inflammatory barrier involves histamine and prostaglandins. Due to infection by microbe, the mast cells release histamine and prostaglandin which cause inflammation. As a result, the capillary wall becomes more permeable to phagocytes and some fluid containing serum protein with anti-bacterial activity. Ultimately, they inhibit and destroy the invading microorganisms.

a) a-connective 

b- epidermis

c – sporogenous tissue 

d-Tapetum 

b) Anther -> sporogenous tissue —> pollen mother cell —> microspore tetrad —> pollen grain —> malegamete

Genetic maps have played an important role in sequencing of genes, DNA fingerprinting, tracing human history, chromosomal location for disease associated sequences (Any one).

No. DNA is more stable

While DNA contains deoxyribose, RNA contains ribose (in deoxyribose there is no hydroxyl group attached to the pentose ring in the 2 position). These hydroxyl groups make RNA less stable than DNA because it is more prone to hydrolysis. DNA have

1. Replication

2. Chemically and structurally stable

3. Obey Mendelian Characters

This type of barrier is called cytokine barrier. The cell infected by virus produce interferons which in turn protect the non-infected cells from further viral infection.

Adaptation for wind pollination

(1) The pollen grains are light and non-sticky

(2) They possess well-exposed stamens and feathery stigma

Adaptation for insect pollination

(1) Insect-pollinated flowers are large, colourful, fragrant and rich in nectar.

(2) The flowers are small, a number of flowers are clustered into an inflorescence 

(b) (1) pollen release and stigma receptivity are not at the same time.

(2) Anther and stigma are placed at different positions so that the pollen cannot come in contact with the stigma of the same flower. Both these devices prevent autogamy.

Identify 20000 - 25000 genes in human DNA., determine 3 billion base pairs, store information as database, improve tool for data analysis, transfer related technologies to other sectors such as industries.