BIOLOGY 2 Marks Questions

Human genome project was considered to be a mega project because it had a specific goal to sequence every base pair present in the human genome. It took around 13 years for its completion and got accomplished in year 2006. It was a large scale project, which aimed at developing new technology and generating new information in the field of genomic studies. As a result of it, several new areas and avenues have opened up in the field of genetics, biotechnology, and medical sciences. It provided clues regarding the understanding of human biology.

Nitrogenous Bases - Adenine, Uracil and Cytosine, Thymine; Nucleosides - Cytidine, guanosine.

The important functions of ribosome during translation are as follows.

• Ribosome acts as the site where protein synthesis takes place from individual amino acids. It is made up of two subunits. The smaller subunit comes in contact with mRNA and forms a protein synthesizing complex where as the larger subunit acts as an amino acid binding site.
• Ribosome acts as a catalyst for forming peptide bond. For example, 23s r-RNA in bacteria acts as a ribozyme.

There are two different types of nucleic acid polymerases.

• DNA-dependent DNA polymerases
• DNA-dependent RNA polymerases

The DNA-dependent DNA polymerases use a DNA template for synthesizing a new strand of DNA, where as DNA-dependent RNA polymerases use a DNA template strand for synthesizing RNA.

S. No.	Translational region	Untranslational region
1.	It is the sequence of ribonucleotides in mRNA, that is flanked by start codon at the 5' end and a stop codon at the 3' end.	These are the sequences of ribonucleotides in mRNA, that are before the start codon at the 5' end and after the stop codon at the 3'end.
2.	This region is translated into a polypeptide.	These sequences are not translated into polypeptide.

DNA packing in eukaryotes is carried out with the help of lysine and argenine rich basic protein called histones. The unit of compaction is nucleosome.

1. Histones are organised to form a unit of eight molecules called histone octamer.
2. The negatively charged DNA is wrapped around the positively charged histone octamer, form a structure called nucleosome.

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Genetic material of retrovirus is RNA. At the time of synthesis of protein, RNA is reverse transcribed to its complementary DNA first, then transcriped to RNA and proteins. Hence, retrovirus are not known to follow central dogma.

When a stop codon UAG/UGA/UAA, presents itself on the mRNA, it has no corresponding tRNA/does not code for any amino acid, release factor binds to the stop codon and translation ends.

In the complete absence of expression of lac operon, permease will not be synthesised which is essential for transport of lactose from medium into the cells. And if lactose cannot be transported into the cell, then it cannot act as inducer. Hence, cannot relieve the lac operon from its repressed state. Therefore, lac operon is always expressed.

These codons are UAA, UAG and UGA. The general name given to these codons is nonsense codons. These codons do not specify any amino acid but the termination of polypeptide chain is signalled by them.

Three major functions of a gene are:

1. It should be able to store information and to express itself when required.
2. It should be heritable from one generation to next.
3. It should be autocatalytic, i.e., should be able to produce its own replica.

DNA polymerase is highly specific to recognise only deoxyribonucleoside triphosphates. Therefore, it cannot hold RNA nucleotides.

1. The 'i' gene codes for the repressor protein, which is synthesised constitutively (all the time).
2. It has a significant role in switching "off" of the operon, as the repressor binds to the operator and prevents the transcription of the structural genes.
3. But in the presence of lactose as inducer, it is inactivated by the interaction with the inducer; the RNA polymerase gets access to the promoter and transcription proceeds, i.e. the operon is switched 'on'.

	Euchromatin		Heterochromatin
i.	Loosely packed	i.	Densely
ii.	Stains light	ii.	Stains dark
iii.	Transcriptionally active	iii.	Transcriptionally inactive

Helicase – opens the helix,

1. Topoisomerases– removes the supercoiling of DNA.
2. Primase: synthesises RNA primer.
3. Telomerase: to synthesises the DNA of telomeric end of chromosomes.

S. No.	Codons	Anticodons
1.	It is a sequence of three nucleotides, which codes for a particular amino acid.	An anticodon is a sequence of three nucleotides that is complementary to the codon of a particular amino acid.
2.	It is found on mRNA and decides the sequence of amino acid in a polypeptide.	It is found on tRNA and recognises the codon on mRNA during translation.

Since RNA was unstable and prone to mutations, DNA evolved from RNA with chemical modifications that makes it more stable.
DNA has double stranded nature and has complementary strands. These further resist changes by evolving a process of repair.

• SNPs: Single nucleotide polymorphisms.
• BAC: Bacterial artificial chromosome
• YAC: Yeast artificial chromosome

In prokaryotes, the DNA is organised in large loops held by positively charged proteins in a region called nucleoid.

Some amino acids are coded by more than one codon (known as degeneracy of codons), hence on deducing a nucleotide sequence from an amino acid sequence, multiple nucleotide sequence will be obtained. For e.g., Ile has three codous: AUU, AUC, AUA hence a depeptide Met–Ile can have the following nucleotide sequence:

1. AUG – AUU.
2. AUG – AUC.
3. AUG – AUA.

And if, we deduce amino acid sequence the above nucleotide sequences, all the three will code for Met–Ile.

Tandemness in repeats provides many copies of the sequence for fingerprinting and variability in nitrogen base sequence in them. Being individual-specific, this proves to be useful in the process of DNA fingerprinting.

1. Sugar.
2. Base.
3. Four (A, T, G, C).
4. Hydrogen.

S.No.	Euchromatin	Heterochromatin
1.	In a nucleus, some regions of chromatin are loosely packed and stain light. These are referred to as euchromatin.	The chromatin that is more densely packed and stains dark are called heterochromatin.
2.	It is transcriptionally active chromatin.	Heterochromatin is inactive.

1. During DNA replication i.e., in the S-phase of interphase enzyme-DNA polymerase.
2. During transcription for protein synthesis-enzyme-DNA dependent RNA polymerase.

1. Reverse transcription is known as teminism, which was first reported by Temin and Baltimore. RNA of some viruses (Retroviruses) first synthesises DNA through reverse transcription. The DNA then transfers information to RNA, which takes part in translation of coded information to form polypeptide.
2. An mRNA has some additional translations which are not coded, these are referred as untranslated regions (UTRs). The UTRs are present at both 5' end (before start codon) and at 3' end (after stop codon). They are required for efficient translation process.

mRNA has some additional sequences that are not translated and are called untranslated regions (UTRs). The UTRs are present both at 3'-end (before the start codon) and at 5'-end (after the stop codon). They only help in efficient translation process.

1. Function of methylated guanosine cap: It regulates nuclear export of mRNA. It promotes translation. (Fully processed hnRNA is called mRNA).
2. Function of poly-A tail: Protects RNA from degradation by exonucleases. Plays important role in transcription termination.

The process by which non-coding regions (intron) on hnRNA are removed and coding regions (exon) are joined to produce mRNA is called splicing. Splicing is necessary in eukaryotes to remove the non-coding introns from hnRNA to produce a meaningful functional mRNA. Prokaryotes do not have introns in the mRNA.

1.  

1. Template strand: It functions as templete to synthesise m-RNA.
2. Promoter: It is a DNA sequence that provides binding site for RNA polymerase.
3. Coding strand: It does not code for any region of RNA.
4. Terminator: It provides DNA sequence which stops transcription.

2. The coding strand will have sequence similar to mRNA strand as this possesses complementary sequence to template strand.

Different DNA marker systems such as Restriction Fragment Length Polymorphisms (RFLPs), Random Amplified Polymorphic DNAs (RAPDs), Amplified Fragment Length Polymorphisms (AFLPs), Simple Sequence Repeats (SSRs) which also called as microsatellites, Single Nucleotide Polymorphisms (SNPs) and others have been developed.

Polarity of the two strands of the fork to be shown and polarity as well as arrow mark of the lagging and leading strands to be shown with correct labelings.

1. It is a stop/ termination codon.
2. UAA or UAG.
3. They terminate the translation process, i.e. they stop the elongation of the polypeptide chain during translation.

1. George Gamow.
2. There are four bases and 20 amino acids.

(There should be at least 20 different genetic codes for these 20 amino acids)

Only possible combinations that would meet the requirement is combinations of 3 bases that will give 64 codons.

Bacteriophage does not have repetitive sequence such as VNTR in its genome as its genome is very small and have all the codon sequenced. Therefore, DNA fingerprinting is not done for bacteriophages.

1. 480 nucleotides.
2. 40,000 nucleotides.

The goals of HGP are as follows:

1. Determine the sequence and number of all the base pairs (three billion) in the human genome.
2. Identify all the genes (25000) present in human DNA.
3. Determine the function of all the genes and identify the various genes that cause genetic disorders.
4. Store the information in data bases.
5. Improve tools for data analysis
6. Find out possibilities of transfer of technology developed during HGP to industry.
7. Address ethical, legal, and social issues (ELSI) that may arise from the project.

Covalent bonds are stronger and tend to hold the backbone together. Hydrogen bonds are much weaker and tend themselves to breaking to enable replication or transcription.

Francis and Crick proposed the central dogma in molecular biology. According to this, genetic information flows from DNA → RNA → Protein. In retroviruses, genetic information flows in reverse direction, i.e. Protein → RNA → DNA. Hence, it is said that retroviruses do not follow central dogma. The process followed by retroviruses is also called reverse transcription because of the opposite sequence of the process involved.

(a)	Unambiguous: One codon codes for only one amino acid.	Universal: Genetic code/codons are(nearly) same for all organisms/from bacteria to human.
(b)	Degenerate: More than one codon coding for the same amino acid.	Initiator: Start codon/AUG.

1.  

2. Basic amino acid residues of lysines, arginines.

1.  

1. AUG: Methionine
2. UUU: Phenylalanine.
3. UAG: No amino acid is coded as it is a stop codon.

2. TAC, AAA, ATC.

Codon	Anticodon
The sequence of 3 nitrogen bases on mRNA that codes for a particular amino acid during translation is called codon.	The sequence of 3 nitrogenous bases on tRNA that are complementary to the codon on mRNA for a particular amino acid during translation is called anticodon.

RNA is more labile and prone to degradation (owing to the presence of 2'-OH group in its ribose). Hence heat-killed S-strain may not have retained its ability to transform the R-strain.

1. AB and CD
2. AB strand
3. CD strand
4. The strands which dictates the sequence of the new strand, is the templete strand. Okazaki pieces are short stretches of DNA synthesised in the 5' 3' direction on discontinuous strand.
5. In 5' → 3' direction.

The DNA-dependent DNA polymerases catalyse polymerisation only in one direction, that is 5' → 3'. This creates some additional complications at the replicating fork. Consequently, on leading strand (the template with polarity 3' → 5'), the replication is continuous, while on the lagging strain (the template with polarity 5' → 3'), it is discontinuous. The discontinuously synthesised fragments are later joined by the enzyme DNA ligase.

An operon is a part of genetic material (or DNA), which acts as a single regulated unit having one or more structural genes, an operator gene, a promoter gene, a regulator gene, a repressor and an inducer or co-repressor The first operon to be discovered was lac-operon.

1.  

1. GUU
2. CCU

2. TAC AAA TAC GGA CAA AGA ATT
3. Stop codon/ Nonsense codon

1. Bacteria.
2. Yeast.
3. Caenorhabditis elegans (a nematode).
4. Drosophila.
5. Rice.
6. Arabidopsis.

Functional mRNA of structural genes need not always include all of its exons. This alternate splicing of exons is sex-specific, tissue-specific, and even developmental stage-specific. By such alternate splicing of exons, a single gene may encode for several isoproteins and/ or proteins of similar class. In absence of such a kind of splicing, there should have been new genes for every protein/ isoprotein. Such an extravagancy has been avoided in natural phenomena by way of altemate splicing.

S.No.	Column A	Column B
(i)	DNA → DNA	Replication.
(ii)	DNA → hRNA	Eukaryotic transcription.
(iii)	mRNA → Protein	Translation.
(iv)	Repressor Protein + Operator → No transcription	Gene regulation.

1. DNA dependent-RNA polymerase
2. hn
3. mRNA
4. Polyadenylate tail

1. Its complementary strand,

5’ – T T A C G T C G A T A A C C – 3’.

2. The mRNA,

5’ – U U A C G U C G A U A A C C – 3’.

Enzymes for DNA replication:

• Various enzymes are required as catalysts during DNA replication in living cells.
• DNA-dependent DNA polymerase: It catalyses the polymerisation of deoxynucleotides on DNA template.
• Helicase: It unwinds the DNA strand to form the replication fork.
• DNA ligase: It joins the Okazaki fragments which are formed on the lagging strand.

Histones are rich in basic amino acids, Lysine, Arginine (present as residues in their side chains), which are positively charged.

Genetic mapping, DNA finger printing.

The 23S rRNA in bacteria is called ribozyme, which catalyses the peptide bond formation.

1. Since hnRNA contains both exons (the coding sequences) and introns (the non-coding sequences), it has to undergo splicing, to remove the introns.
2. Splicing occurs in the nucleus of the cell.

The possible regulation of gene expression can occur at following:

1. Transcriptional level, i.e. during formation of primary transcript.
2. Processing level (during splicing).
3. During transport of mRNA from the nucleus to the cytoplasm
4. Translational level.

1. Write the base sequence of the RNA got after transcription of the given sequence.
2. What is the distance maintained between the two consecutive pairs of bases in the DNA molecule?
3. Who contributed the base complementary rule?

1. It is a DNA sequence that provides the binding site for RNA polymerase for transcription.
2. It is located towards the 5' end (upstream) of the structural gene (of the coding strand).

Stop codon - Does not code for any amino acid/terminates the synthesis of polypeptide chain.
Unambiguous codon - One codon codes for one amino acid only.
Degenerate codon - Some amino acid are coded by more than one codon.
Universal codon - Genetic code is same for all organisms (bacteria to humans).

Introns: The non-coding region of DNA or gene are called introns.
Exons: The coding region of DNA or gene which translate polypeptide are called exons. RNA splicing is the process that removes the unwanted RNA region and joins those that code for amino acids.

1. Terminator is a sequence of DNA that defines the end of transcription.
2. It is located towards the 3' end (downstream) of the coding strand.

VNTR-Variable Number Tandem Repeats,
Probe- is labelled/radioactive (single stranded hybridise DNA fragments).

1. DNA polymerase uses a DNA template to catalyse the polymerisation of deoxynucleotides during the process of DNA replication.
2. RNA primer is removed from the 5' end by the exonuclease activity of DNA polymerase.
3. DNA polymerase is also involved in proof-reading and DNA repair. The wrongly introduced bases can be removed by the activity of this enzyme.

DNA fingerprinting is used in:

1. DNA forensics, for identification of criminals
2. DNA fingerprinting, for solving paternity disputes
3. Determining population and genetic diversities
4. Studying the breeding patterns of animals facing the danger of extinction.

The two DNA strands run parallel to each other but in opposite direction. In one chain the direction is 5' 3' while in the other one it is 3' 5'.

The genetic code is nearly universal, i.e. particular codon codes for the same amino acid in all organisms except in mitochondrial codons and few Protozoans.

(Discontinuous) DNA fragments are joined/sealed by them. // sticky ends of vector and foreign DNA, joined by them. The following diagram can be considered in lieu of explanation.

Repeated sequences make up very large portion of the human genome. Repetitive sequences are stretches of DNA sequences that are repeated many times, sometimes hundred to thousand times. They are thought to have no direct coding functions, but they shed light on chromosome structure, dynamics and evolution. Less than 2 percent of the genome codes for proteins.

James Watson and Francis Crick in 1953.

For long DNA molecules, since the two strands of DNA cannot be separated in its entire length (due to very high energy requirement), the replication occur within a small opening of the DNA helix, referred to as replication fork.

1. Ribose.
2. 3' - 5' phosphodiester linkage.
3. B- is 3' end.

Here the ribose has a free 3' OH group.

Distance between two consecutive base pairs = 0.34 × 10 - 9m
The length of DNA in bacteriophage lambda = 48502 × 0.34 × 10 - 9m = 16.49 × 10 - 6m

The mutation in which addition/ insertion or deletion of one or two bases changes the reading frame from the site of mutation is called frameshift mutation. It may result in polypeptide with different sequences of amino acid. A disease caused by frameshift mutation is muscular dystrophy.

After the elongation as the polymerase reaches the terminator region, the nascent RNA along with RNA polymerase fall off. RNA polymerase associates transiently with the termination factor-Rho (p) to terminate the transcription.

The genes present in an organism show a particular trait by way of forming certain product. This is facilitated by the process of transcription and translation (according to central dogma of Biology)

DNA (being negatively charged) is held with some proteins (that have positive charges) in a region termed as ‘nucleoid’. The DNA in nucleoid is organised in large loops held by proteins. Also the DNA in form of single chromosomes is attached to mesosome at a point.

2’, 3’ - dideoxy cytidine triphosphate is a reverse transcriptase inhibitor. Reverse transcriptase is a viral DNA polymerase which facilitates DNA replication in HIV and other retroviruses. The commercial name of ddC is Zalcitabine and it is sold as a pharmaceutical product for management of HIV. If 2’, 3’ - dideoxy cytidine triphosphate is used as a raw nucleotide in place of 2’ - deoxy cytidine, it will stop DNA replication. The researcher will not be able to proceed on his experiment because of contrary effect of his chosen reagent.

1. Initiation
2. mRNA codon = AUG

3. The densely packed and dark stained/ transcriptionally inactive chromatin is known as the heterochromatin.

1. Monocistronic RNA:

• It is the length of RNA which has information to code for one polypeptide; it is found mostlyin eukaryotes.

2. Polycistronic RNA:

• It is a long mRNA, which has information to code for more than one polypeptide; it is found in prokaryotes.

1. The codon AUG is the initiation codon and codes for methionine, the initiator amino acid.
2. UAG is a stop codon that does not code for any amino acid and brings about the termination of the translation process.

Amino acids are activated in the presence of ATP and linked to (cognate) t-RNA.
Carries amino acid to the site of protein synthesis/reaches amino acids to the respective codon.

A unit of eight molecules of positively charged histones, negatively charged DNA, wrapped around the histones octamer, contains 200 bp of DNA helix.
DNA is negatively charged, histone is positively charged, 200 bp of DNA helix.

S. No.	Cistron	Exon
1.	A cistron is a segment of DNA coding for a polypeptide.	Exon is the coding sequence or expressed sequence of DNA/ hnRNA.
2.	It includes both introns and exons.	Only exons appear in a mature or processed mRNA.

Retroviruses carry reverse transcriptase. This enzyme catalyses the formation of DNA from RNA which integrates with DNA of host cell.

1. Ribozyme catalyses the formation of peptide bond in bacteria.
2. The release factor binds to the stop codon and terminates translation and releases the polypeptide synthesised.

RNA is more labile and prone to degradation (owing to the presence of 2’ OH group in its ribose). Hence heat-killed S-strain may not have retained its ability to transform the R-strain into virulent form if RNA was its genetic material.

Both the strands of DNA are not copied during transcription for the following reasons:

1. 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.
2. The two complementary RNA molecules (produced simultaneously) would form a double-stranded RNA rather than getting translated into polypetides.
3. RNA polymerase carries out polymerisation in the 5' → 3' direction and hence, the DNA strand with 3' → 5' polarity acts as the template strand.

1. M is the repressor.
2. When the repressor binds to the operator, transcription of structural genes by RNA-polymerase is prevented.
3.  

1. An inducer can prevent the binding of repressor to operator.
2. Consequently, the RNA-polymerase gets access to the promoter and transcription proceeds.

Variability in number of tandem repeats (VNTR) is highly useful in DNA finger printing. DNA sample is subjected to gel electrophoresis or Southern blotting. After that VNTR manifests as a pattern of lines of different lengths. The variability in lengths of lines and their respective arrangement varies from one individual to another. This is more or less unique the way a person’s finger print is. Thus, VNTR helps in establishing exact identity of an individual through DNA finger printing.

The amino acids are activated in the presence of ATP and linked to their cognate tRNA. This process is called charging of tRNA or amino-acylation of tRNA. When two such charged tRNAs are brought close enough, the formation of peptide bond between them would be favoured energetically. The presence of a catalyst would enhance the rate of peptide bond formation.

The terminator is a component of transcription unit, which defines the end of the process of transcription. It is a code on the mRNA for which the tRNA has no anticodon and so the polypeptide chain breaks.

One nucleosome contains approximately 200 base pairs of DNA helix. Nucleosomcs are the repeating units of chromatin, which are threadlike stained 1colo"r.d) bodies. present in nucleus, The nucleosomes in chromatin look like 'beads-on-string' when observed under an Electron Microscope (EM).

Codes for Methionine, and is an initiation codon.The sequence of bases from which it is transcribed is T AC.
Its anticodon is UAC.

1. Repressor Lactose (inducer) binds with the repressor molecule.
2. Z gene.
3. When all the lactose molecules are consumed/repressor becomes free to bind with operator.

The process of multiplication of DNA by subjecting the desired DNA to polymerase chain reaction is called amplification.

Functions of RNA:

1. It functions as a messenger and brings the genetic information of DNA to ribosomes.
2. It is an adapter, i.e., it transports specific amino acid and reads the codon on mRNA.
3. It is a structural component of ribosomes.
4. It also acts as a catalyst in prokaryotes for peptide bond formation.

Provides the sites for the binding of amino acid, acts as a catalyst (23S r RNA) for the formation of peptide bond ATP provides the energy for the bond formation.

Bacteriaphage does not have repetitive sequences such as VNTRs in its genome as its genome is very small and have all the coding sequence. DNA finger printing is not done for phages.

1. AUG GGG GUG CUC AAU AUA UAU GCC CCC GUA GUA UAC
2. AUG GGG GUG AAU AUA UAU GUA GUA
3. 8 amino acids.

tRNA is an adaptor molecule, which is meant for transferring amino acids to ribosomes for synthesis of polypeptides, tRNAs carry specific amino acids at particular points during polypeptide synthesis as per codons of mRNA, and the codons are recognised by anticodons of tRNAs. Thus, the coded information from DNA is translated by bringing amino acids in a particular sequence.

S. No.	Replication	Transcription
1.	When replication starts, the total DNA of the organism replicates.	In transcription, only a segment of one of the strands is copied.
2.	Adenine pairs with thymine.	Uracil is the complementary base for adenine.

1. TAC
2. AUG
3. Methionine
4. ACC
5. ACC
6. UUC
7. AAG
8. Phenylalanine
9. GAC
10. CUG
11. Leucine

1. TAC CTG GAC TAT AAA ACT
2. Five amino acids.

Presence of H-bonds, the plane of one base pair stacks over the other, complementarity, presence of thymine in place of uracil.

Structural genes are those genes which actually synthesise mRNAs. The lac operon of Escherichia coli contains three structural genes (z, y and a).

1. Deoxyribose.
2. Two nucleotides are linked through 3' → 5' phosphodiester linkage to form a dinucleotide.
3. B is 3' end, here the sugar has a free 3' OH group.

	Prokaryotes	Eukaryotes
1.	Polycistronic	Monocistronic.
2.	No split genes / Not interrupted coding sequence	Split genes/interrupted coding sequences/exon and intron.

1. RNA functions as an enzyme and is therefore reactive and unstable.
2. Uracil present in the RNA is less stable as compared to thymine of DNA.
3. Being unstable RNA mutates at a much faster rate, that is why RNA viruses have shorter life span and mutate and evolve very fast. Such rapid changes are harmful to higher forms of life.

1.  

1. AUG signals the synthesis of polypeptide (start signal) and codes for the amino acid methionine.
2. UUU codes for phenylalanine.
3. UAG do not specify any amino acid and hence is called nonsense codon. It signals the termination of polypeptide chain (stop signal).

2. TACAAAATC

The two factors/ assumptions are that:

1. Genetic make up of an organism lies in the DNA sequences.
2. Iftwo individuals differ, then their DNA sequences should also be different.

After DNA replication, the daughter DNA formed contains one parental strand and one newly synthesised strand. Such type of DNA replication is called semi-conservative DNA replication.

1. If it behaves as starting codon it will bind at P site, otherwise it will bind at A site.
2. UAC
3. AUG
4. Aminoacyl tRNA synthetase.

1. Lactose is the inducer for lac operon.
2. The active form of lactose binds to the repressor protein and brings about a conformational change in the repressor.
3. As a result, the repressor is inactive, i.e. it cannot bind to the operator.
4. This provides access of the RNA polymerase to structural genes and transcription and production of enzymes continue and metabolism of lactose takes place.
5. In its absence, the repressor is active and binds to the operator, thereby switching off the process.

Francis Crick proposed the presence of an adapter molecule, i.e. rRNA.

1. It has an amino acid binding end; so it transports a specific amino acid to the site of protein synthesis.
2. By its anticodon, it recognises the codon at the A site and binds to it by hydrogen bonds and ultimately releases the amino acid it carries.

The possible levels of regulation in eukaryotes could be at:

1. Transcriptional level, i.e. formation of primary transcript.
2. Processing level, i.e. regulation of splicing.
3. Transport of mRNA from the nucleus to the cytoplasm.
4. Translational level.

1. ACGUCG- at the 5' end before the initiation codon.
2. GAGGAA- at the 3' end after the termination codon.
3. They are normally located in front of the initiation codon at the 5' end and behind the termination codon at the 3' end of the coding strand of DNA.

Bacteria and yeast are the hosts.
Bacterial Artificial Chromosomes (BACs) and Yeast Artificial Chromosomes (YACs) are the vectors.

S. No.	Codons	Anticodons
1.	A codon is a sequence of three nucleotides, which codes for a particular amino acid.	An anticodon is a sequence of three nucleotides that is complementary to the codon of a particular amino acid.
2.	It is found on mRNA and decides the sequence of amino acids in a polypeptide.	It is found on tRNA and recognises the codon on mRNA during translation.

Properties of Genetic Material:

1. The genetic material should be able to generate its replica so that one can be transmitted to the daughter cell/ next generation.
2. It should be chemically and structurally stable.
3. It should provide scope for slow changes (mutation) that are necessary for evolution.
4. It should be able to express itself in the form of Mendelian characters.

Cistron is a segment of DNA coding for a polypeptide. In eukaryotes the transcriptional unit have interrupted coding sequences - exons and introns. It codes for only one polypeptide, so it is called monocistronic.
In prokaryotes structural genes have many coding sequences, so it is called polycistronic.

The Role of RNA Primers During DNA replication, two pieces of DNA are separated and used to build new complementary strands of DNA. After the RNA primer has been made, DNA polymerase will bind to it and start creating a new strand of DNA by adding complementary nucleotides to the primer.

By phosphodiester bond.

1. Deletion.
2. Duplication.
3. Inversion.

It will code for 19 amino acids because, the last codon on mRNA will be a terminating codon, which will not code for any amino acid.

To compensate the loss of male gametes during their transport(to the non-motile female gamete) through water/to increase chances of fertilisation, antherozoids.

1. Binding of inducer/lactose to the repressor.
2. In the absence of inducer lactose/when repressor binds with the operator.
3. ß - galactosidase.

S.No.	Leading strand	Lagging strand
1.	It is a replicated strand of DNA which grows continuously without any gap.	The lagging strand is a replicated strand of DNA which is formed in short segments called discontinuous.
2.	It does not require DNA ligase for its growth.	DNA ligase is required for joining okazaki fragments.
3.	The direction of growth of a leading strand is 5' → 3'.	The direction of the lagging strand is 3' → 5'.
4.	Only a single RNA primer is required.	Starting of each okazaki fragment requires a new RNA.
5.	Its template opens in 3' → 5' direction.	Its template opens in 5' → 3' direction
6.	Formation of leading strand begins immediately at the beginning of replication	Formation of lagging strand begins a bit later than that of leading strand.

The DNA of the two claimants father and the daughter is extracted from the nuclei of white blood cells. The DNA molecules are then used for obtaining DNA finger prints (DNA profiles). Now the DNA fingerprints are matched to identify the real father.

1. Helicase: Helicase opens the helix.
2. Topoisomerases: Removes the supercoiling of DNA relieves the tension due to unwinding.
3. Primase: Synthesises RNA primer.
4. Telomerase: To synthesises the DNA of telomeric end of chromosomes.

1.  

2. Law of independent assortment.

Methylated guanosine cap helps in binding of mRNA to smaller ribosomal sub-unit during initiation of translation. Poly-A tail provides longevity to mRNA’s life. Tail length and longevity of mRNA are positively correlated.

If histone proteins were rich in acidic amino acids instead of basic amino acids then they may not have any role in DNA packaging in eukaryotes as DNA is also negatively charged molecule. The packaging of DNA around the nucleosome would not happen. Consequently, the chromatin fibre would not be formed.

These assumptions led to the idea of determining the complete DNA sequence of human genome and consequently of human genome project. It was a mega project which took 13 years for its completion, i.e. from 1990 to 2003. It was coordinated by the US Department of Energy and the National Institute of Health.
The two main factors that contributed in the completion of this project are-

1. Availability of simple and fast techniques for the determination of DNA sequences.
2. Genetic engineering techniques, which help to isolate and clone any segment of DNA.