164Sinior Botony

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AnswersSection-I

1) ! Imbibing capacity of peaseeds is morethan wheat seeds because pea seeds are rich in proteins and

wheat seeds are rich in starch.

!Proteinaceous pea seeds swell more on imbibing water than starchy wheat seeds.

2) ! Apoenzyme - The protein part of holoenzyme.

! Co-factor - Non protein partof holoenzyme.

3) ! The internodal elongation just before flowering is called bolting. Eg - Beet, cabbage.

! Gibberellins are responsible for bolting.

4) ! Bacteria that change their shape depending up on the environment and nutrients available are called

the pleomorphic bacteria.

! Eg - Aceto bacter.

5) ! The Physical or external appearance of a character is called phenotype.

! The genetic make up of an individual is called geno type.

6) Capping - The process of addition of melty guanosine triphosphate to the 51 end of hn RNA is termed

ascapping.

Tailing - The process of addition of adenylate residues (200-300) to the 31 end of hn RNA is termed as

tailing.

7) ! In the given data purines and pyramidines did not exist in 1:1 ratio.

! The nucleic acid is RNA which is single stranded.

8) ! Restriction endonucleases are called molecular scissors.

! These are mostly obtained from bacterial cells.

9) ! Large vessels meant for culturing microbes on large scale are called Fermentors.! Fermentors are used to synthesize a number of products valuable to human beings.

Eg - Beverages, Antibiotics.

10) Bt-Cotton, Bt-Bringal

Section-II

11) Advantages:

! It creates transpiration pull for absorption and transportation of water inplants. It supplies water for

photosynthesis.

! Transports minerals from the soil to all parts of a plant. Cools leaf surgaces, sometimes 10 to 15

degrees, by evapurative cooling.! Maintains the shape and structure of the plants by keeping cells turgid.

Disadvantages

! An actively photosynthesizing plant has an insatiable need for water.

! Photo synthesis is limited by available water which can be swiftly depleted by transpiration.

! Excess transpiration cames wilting.

! Some plants shed their leaves during the periods of low water availability inorder to check transpira-

tion. By observing above advantages and disadvantages curtis described transpiration as ‘necessary

evil’.

12) ! Rhizobium bacteria are attracted by sugars and amino acids released by the legume roots.! Rhizobium bacteria multiply and get attatched to epidermal cells and root hairs.

! The bacteria induce the root hairs to curl at their tips.

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! Bacteria invade the root hairs, and an in fection thread is produced and carry the bacteria into the

inner cortex of the root. The internal tubular infection is called infection thread.

! Then the bacteria released from the thread into the cortical cells become becteroids which stimulate

the cortical and pericycle cells to divide.

! The division and growth of cortical and pericycle cells lead to nodule formation by differentiation.

!The nodule thus formed establishes a direct vascular connection with the host for exchange of nutri-ents.

13) ! Plants that are adapted to dry tropical regions have the C4 path way. Though these plants have the C4OAA as the first CO

2 fixation product, they use the C

3 path way as the main bio synthetic path way.

! C4 plants have special type of leaf anatomy. Which is not thing but-Kranz anatomy.

! Kranz means wreath

! C4 path way takes place with the co-ordination of mesophyll cells and bundle sheath cells.

! PEP accepts CO2 to form a four carban compund OAA in the presence of PEP carboxylase. This step

occurs in esophyll cell.

! OAA later enters in to the chloroplast of mesophyll cell. OAA undergoes reduction to form malicalid.

! Later malicalid enters into the chloroplast of bundle sheath cell, there it undergoes oxidation and

decarbo xylation to form pyruvicalid in the presence of malic enzye. The CO2 take part in C3 Cycle.! Pyruvic acid enters into the chloroplast of esophyll cell, there it utiliser 2ATP’s to form PEP, which

is the first CO2 acceptor. This step taken place in the presence of pyruvic kinase.

14) ! Auxins help to initiate rooting in stem cuttings. This property is widely used in agriculture.

! Auxins promote flowering. Eg - Pineapples.

! They help to prevent fruit and leaf drop at early stages but promote the abscission of older leaves and

fruits.





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! Auxins responsible for apicaldominance. However decapitation results in the growth of lateral buds.

This phenomenon is generally used in tea plantation and hedge making.

! Auxins also unduce parthenocarpy. Eg - Tomatoes.

! Auxins are widely used as herbicides. Eg - 2, 4-D widely used to kill dicotyledonous weeds with

broad leaves.

!2, 4,-D is used to prepare weed free lawns by gardeners.

15) Structure of TMV:

! TMV is a rod shaped virus.

! It is a 300 mm long and 18 mm in diameter with 39x106 daltons of molecular weight.

! It shows a hollow space of 4 mm diameter.

! It is surrounded by a protein coat called the capsid. The capsid is made up of 2130 capsomeres.

! The capsomeres are arranged helically around the central core.

! Each protein sub unit is made up of 158 amino acids.

! It’s genetic material is a single stranded RNA with 6500 nucleo tides.

16) Co-doinance:

! The phenomenon of neither the allele of a gene is dominant nor recessive to the other, so that the

heterozysotes show the phenotype of both the parents.

! Eg - Seed coal- patfern and size in Lentils.

! When a cross is made in lentils between pure breeding spotted plant and purebreeding dotted plant,

the F1 heterozygotes resulted with both spotted and dotted phenotypes.

! On selfing of F1 plants, the F

2 plants showed the phenotypes as 1 spotted: 2 spotted & dotted: 1

dotted.

! The heterozygotes differ from both the homozygotes in phenotype and genotype and hence both

phenotypic and genotypic ratios coincide.





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17) DNA RNA

! It is double stranded ! It is single stranded

! Deoxyribose sugar is present ! Ribose Sugar is present

! Pyramidines are T & C ! Pyraidines are U & C

! It is made up of several nucleotides ! It is ade up of few nucleotides.

! It undergoes self replication ! Does not under go self replication except RNA viruses.

! It is the genetic material ! It is non genetic material except RNA viruses.

! It does not participate directly

in protein synthesis ! Participates directly in protein synthesis.

! Metabolically it is of one type ! Metabolically it is of 3 types.

18) Pest resistant plants:

! Some nematodes like meloidegyne in cognitia infect roots of tobacco plant and results in reduced

yield.

! To prevent this infestation meehanism of RNA interference is employed. Nematode specific genes

are introduced in to the host plant by using Agrobacterium as a vector.

! The introduced DNA produce both sense and anti sense RNA’s with in the host cells. These two

RNA’s combine to form a double stranded RNA that initiate RNAi and silence the particular mRNA

of nematode.

! The chances of survival of parasite in the transgenic host with specific interfering RNA is less. Thus,

the transgenic plant gets protected from the parasite.

Section-III

19) Krebs cycle/TCA Cycle/Citricacid Cycle

! Pysuvate enters the mitochandrial matrix and under goes oxidative decarboxylation. The complex

set of reactions catalysed by pyruvic dehydrogenase require the participation of several co-enzymes

including NAD+ and coenzye A

Pyruvicacid + COA+NAD+

Pyruvate

dehydrogenase

Acety/COA+CO2+NADH+H+

! Acety/COA acts as substrate for krebs cycle.

! Krebs cycle may also be called as ‘TCA’ cycle.

! Krebs cycle is also called as citricalid cycle.1) Condensation:

Condensation of Acety/COA with OAA and water to yield citricacid in the presence of citric synthetase

and Co-A is released.

OAA+ Acety/COA+H2O Citric Synthetase Citricacid+CO-A

2) Dehydration:

Citric acid undergoes dehydration to form cis aconiticalid in the presence of aconitase.

Citric acid Aconitase Cis-Aconitic acid + H2O.

3) Hydration:

Cisaconitic acid undergoes hydration to form ISO Citric acid in the presence of aconitase.

Cis-aconitic acid + H2O Aconitase ISO Citricacid.

4) Oxidation-I:ISO Citric acid undergoes Oxidation in the presense of ISO Citric dehydrogenase to yield Oxalo succeinic

acid.

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ISO Citric acid + NAD+ ISO Citric delydrogenase. Oxalosucceinic acid+NADA+H+]

5) Decarboxylation:

Oxalosucceinic acid undergoes decarboxylation in he presence of oxalosucceinic decarboxylase to form -

! - Keto glutaric acid.

Oxalosucceinic acid Oxalosucceinic decarboxylase ! - Ketoglutaric acid + CO2.

6) Oxidative decarboxylation, Oxidation-II:

-Ketoglutaric acid undergoes Oxidation decarboxylation in the presence of ! -Ketoglutaric dehydroge-

nase and condenses with Co-A to form succeimy/COA.

! - Ketoglutaric acid + NAD+ + Co-A

! -Ketoglutaric dehydrogenase

Succeinyl COA + NADH + H+ + CO2.

7) Cleavage:

Succeiny/COA splits into succeinic acid and CO.A in the presence of succeinic thiokinase to form succinic

acid. The energy released is utilised to form ATP from ADP and Pi.

Succiny/COA+ADP+Pi Succinic thiokinase Succinicacid + ATP+COA

8) Oxidation-II:

Succeinic acid undergoes Oxidation and forms fumaric acid in the presence of succinic dehydrogenase

Succinic acid + FAD Succinic dehydrogenase. Fumaric acid + FADH29) Hydration:

A water molecule is added to fumaric acid in the presence of fumerase to form alic acid.

Fumaric acid + H2O Fumerase Malic acid.

10) Oxidation-IV:

Malic acid undergoes Oxidation in the presence of malic dehydrogenase to form OAA.

Malic acid + NAD+ Malic dehydrogenase OAA + NADH + H+

20) Recobinant DNA technology involves several steps as follows.

A) Isolation of DNA

B) Fragmentation of DNA by REN

C) Isolation of desired DNA fragment

D) Ligation of desired DNA fragment into a suitable Vector.

E) Insertion of r-DNA into the host cell

F) Selection of transformed cells.

G) Obtaining the foreign gene product.

H) Down stream processing.

A) Isolation of DnA:

! Bacterial cells, plant cells, fungi and anial cells are treated with lysozyme, cellulase, and chitinare as

per requireent to dissolve their cell walls.

! RNA can be separated by treating with ribonuclease.

! Enzyme protease is used to reove proteins.

! After separation of other olecules, purified DNA is precipitated out by adding chilled ethanol.

B) Fragentation of DNA by restriction endonucleares:

! Cutting of DNA at specific location can be achieved by using restriction enzyes.

! This purified DNA is incubated with the specific restriction enzyme at conditions optimum for the

enzyme to act.

C) Isolation of desired DNA fragment:

! This process is carried out by using the agarose gel electrophoresis. As the DNA fragments are

negatively charged, they migrate towards the positive anode and thus, DNA fragments are separated

out. The DNA fragments of different sizes are isolated by elution.

!The desired DNA fragment is selected through southern blotting technique.

! Amplification of specific DNA sequences is carried out invitro by using PCR.

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D) Ligation of the desired DNA fragment in to a suitable Vector:

! It requires a Vector and source DNA

! These are cut with the same restriction endonuclease to obtain same stichyends.

! Both are then ligated by mixing Vector DNA and gene of interest by enzyme DNA ligase to form

recombinant DNA.

E) Insertion of r - DNA in to the host cell:

! The receipient cells are made competent to receive and take up the DNA present in their surroundings.

! The r - DNA along with the host cells are first incubated in a specific concentration of a divalent

cation such as calcium.

! In the next step, the host cells along with r-DNA are incubated on ice, followed by placing them

briefly at 420C and then putting them back on ice.

! This enables the bacteria to take up r - DNA.

! There are other direct methods of insertion of r- DNA like micro injection, genegun etc.,

! The receipient cell carrying r- DNA is called transformed cell.

F) Selection of transformed host cells:

! If r-DNA carrying antibiotic resistance gene is transformed into E.Coli Cells, the host cell is trans-

formed into ampicilin resistant cell.

! The apicilin resistant gene can be called selectable marker.

! When transformed cells are grown on agar plates containing ampicilin, only transformants will grow

and other will die.

! Selection of transformed cells can also be carried out by insertional inactivation and colony hybrid-

ization.

G) Obtaining the foreign gene product:

! It is carried out in appropriate medium at optimal conditions. The DNA gets multiplied and express

itself to form desired products.

! A protein encoded gene expressed in a heterologous host is called recombinant protein.

! In a large scale, cells are grown in a continuous culture syste in which fresh medium is added from

one side to maintain cells exponential growth phase and the desired protein is collected from the

otherside.

H) Downstream processing:

! After completion of the biosynthetic stage the product is subjected to a series of processes, that

include separation and purification which are collectively called down stream processing.





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21) The main steps in breeding a new genetic Variety of a Crop are:

1) Collection of Variability:

! Genetic Variability is the root of any breeding programme. generally pre existing genetic variability

is available from wild relatives of crop plants.

! Collection and preservation of all the different wild varieties, species and relatives of he cultivated

species is a prerequisite for effective exploitation of natural genes available in the population.

! The entire collection of plants/seeds having all the diverse alleles for all genes in a given-crop is

called germplas collection.2) Evaluation and Selection of parents:

! A germplasm is evaluated so as to identify plants with desirable combination of characters.

! The selected plants are multiplied and used in the process of hybridization.

! Purelines are created whereever desirable and possible

3) Cross hybridization among the parents:

! The desirable characters have often to be combined from two different plants (parents)

! For example, high protein quality of one parent may need to be cobined with diseare resistance from

another parent.

! This is possible by cross hybridizising the two parents to produce hybrids that genetically combine

the desired characters in one plant.! This is a very-time consuming and tedicious process since the pollengrains from the desirable plant

chosen as ale parent have to be collected and placed on the stigma of flowers selected as female

parent.

! Also it is not necessary that the hybrids do combine the desirable characters.

! Usually only one in a few hundred to a thousand crosses shows the desirable cobination.

4) Selection and testing of superior recombinants:

! This step consists of selecting, among the progeny of the hybrids, those plants that have the desired

character combination.

! The selection process is crucial to the success of the breeding objective and requires careful scien-

tific evaluation of the progeny.! This step yields plants that are superior to both the parents.

! These are self pollinated for several generations till they reach the state of homozygosity, so that the

characters will not seggregate in the progeny and remain stable.

5) Testing, release, and commercialization of new cultivar:

! The newly selected lines are evaluated for their yield and other agronomic traits of quality, disease

resistance, etc.,

! This evaluation is done by growing these in research fields and recording their performance under

ideal fertilizer application, irrigation and other cropmanagemenl practices.

! The evaluation in research fields is followed by testing the materials in farmers fields, for at least

three growing seasons at several locations in the country, representing all the agroclimatic zones

where the crop is usually grown.

! The material is evaluated in comparision to the best available local crop cultivator-a-check or refer-

ence cultivar.


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164Sinior Botony