10th Science Unit 20 Breeding and Biotechnology Book Back Answers

1. a) clonal selection
2. b) mass selection
3. c) pureline selection
4. d) hybridisation

1. Mass selection only needs collecting seeds of the best-looking plants from a mixed population, judged by morphological characters.

2. It needs no technical skill like emasculation or clonal propagation, so even an inexperienced farmer can do it.

1. a) sugarcane
2. b) rice
3. c) cow pea
4. d) maize

1. Table 20.1 lists Pusa Komal as the variety resistant to bacterial blight.

2. This variety belongs to cowpea.

1. a) chilli
2. b) maize
3. c) sugarcane
4. d) wheat

1. Himgiri is resistant to leaf and stripe rust and hill bunt.

2. These are diseases of wheat, so Himgiri is a wheat variety.

1. a) IR 8
2. b) IR 24
3. c) Atomita 2
4. d) Ponni

1. IR-8 is the high-yielding semi-dwarf rice developed by IRRI, Philippines, and introduced in 1966 in Philippines and India.

2. It is popularly called 'Miracle rice'.

1. a) enzyme from organism
2. b) live organism
3. c) vitamins
4. d) both (a) and (b)

1. Biotechnology uses living organisms and their enzymes (such as restriction enzymes and DNA ligase) to make useful products like insulin and vaccines.

2. Vitamins are products, not tools, so both (a) and (b) is correct.

1. a) scissors
2. b) restriction endonucleases
3. c) knife
4. d) RNAase

1. Restriction enzymes (restriction endonucleases) recognise a specific palindromic sequence and cleave the phosphodiester bond in DNA.

2. Hence they are called molecular scissors.

1. a) vector DNA
2. b) circular DNA
3. c) recombinant of vector DNA and desired DNA
4. d) satellite DNA

1. In genetic engineering the desired DNA fragment is inserted into a vector such as a plasmid.

2. The new DNA formed by joining DNA from two different sources is recombinant DNA (rDNA).

1. a) single stranded
2. b) mutated
3. c) polymorphic
4. d) repetitive

1. DNA fingerprinting analyses satellite DNA made of small repeated stretches.

2. The number of these Variable Number of Tandem Repeats (VNTRs) differs from person to person, so repetitive sequences are identified.

1. a) transgenic organsims
2. b) genetically modified
3. c) mutated
4. d) both a and b

1. Plants or animals expressing a modified endogenous gene or a foreign gene (transgene) are produced by rDNA technology.

2. They are called both genetically modified organisms and transgenic organisms.

1. a) n = 7 and x = 21
2. b) n = 21 and x = 21
3. c) n = 7 and x = 7
4. d) n = 21 and x = 7

1. Given $2n = 6x = 42$.

2. Haploid number $n = \dfrac{42}{2} = 21$.

3. Basic number $x = \dfrac{42}{6} = 7$.

1. Plant breeding is the art of developing economically important plants with superior quality.

1. Under biofortification, Atlas 66 is listed as a protein rich wheat variety.

1. Polyploidy can be induced by chemical agents; colchicine is used to double the chromosome number (e.g. in Triticale and Raphano brassica).

1. Biofortification is the scientific process of developing crop plants enriched with high levels of desirable nutrients like vitamins, proteins and minerals.

1. Among achievements of mutation breeding, Atomita 2 rice shows saline tolerance and pest resistance.

1. Genetic engineering is the manipulation and transfer of genes to create recombinant DNA, so it is also called recombinant DNA (rDNA) technology.

1. Restriction enzymes recognise a specific palindromic base pair sequence in DNA and cleave it there; this site is called the restriction site.

1. The DNA pattern of two individuals cannot be the same except for identical twins.

1. Unlike differentiated cells, stem cells are undifferentiated or unspecialised mass of cells.

1. In gene cloning the isolated DNA fragment is inserted into a suitable vector (plasmid) to make rDNA.

1. The textbook lists Raphano brassica under achievements of polyploidy breeding.

2. It is an allotetraploid produced by colchicine treatment, so it is man-made.

1. An organism having more than two sets of chromosomes is called polyploid, and the condition is polyploidy.

2. Mutation is a sudden heritable change in the nucleotide sequence of DNA, which is different.

1. Plants produced from a single plant by vegetative or asexual reproduction are called clones.

2. Pureline is the progeny of a single individual obtained by self breeding (seed, not vegetative).

1. Iron rich fortified rice is an example of biofortification for mineral content.

2. It improves the iron (mineral) quality of the crop, not the protein quality.

1. Golden rice is produced by inserting the beta carotene gene into rice using rDNA technique.

2. So it is a genetically modified (transgenic) plant, not a hybrid obtained by crossing.

1. The Bt gene is taken from the bacterium Bacillus thuringiensis.

2. It produces a protein that is toxic to insects, giving insect resistant plants.

1. 'In vitro' means outside the living body, in glassware or a laboratory dish.

2. So in vitro fertilisation is fertilisation carried out outside the body.

1. The textbook states that the DNA fingerprinting technique was developed by Alec Jeffrey.

2. It identifies individuals using VNTRs of satellite DNA.

1. Restriction enzymes cut or break DNA at specific sites, so they are called molecular scissors.

2. DNA ligases join the broken DNA fragments, so they act as molecular glue.

1. a) Assertion is correct and reason is wrong
2. b) Reason is correct and the assertion is wrong
3. c) Both assertion and reason is correct
4. d) Both assertion and reason is wrong.

1. Assertion: True. Hybridisation brings the desired characters of two or more parents into one progeny, and the hybrid is superior in one or more characters to both parents (heterosis or hybrid vigour).

2. Reason: True. Continued inbreeding causes inbreeding depression — it reduces fertility and productivity, so the vigour of the hybrid is lost.

3. Both statements are true, hence option (c).

1. a) Assertion is correct and reason is wrong
2. b) Reason is correct and the assertion is wrong
3. c) Both assertion and reason is correct
4. d) Both assertion and reason is wrong.

1. Assertion: False. Colchicine is a chemical agent used to induce polyploidy — it doubles (increases) the chromosome number, as in making the sterile wheat–rye hybrid into hexaploid Triticale (2n = 42).

2. Reason: False. Colchicine acts by preventing spindle formation, so the sister chromatids are not pulled to opposite poles; this is what leads to doubling of chromosomes.

3. Since both statements are wrong, option (d) is correct.

1. a) Assertion is correct and reason is wrong
2. b) Reason is correct and the assertion is wrong
3. c) Both assertion and reason is correct
4. d) Both assertion and reason is wrong.

1. Assertion: True. Recombinant DNA technology is superior to hybridisation because only the selected gene is transferred, and the gene can even be taken from an unrelated organism (e.g. Bt gene from Bacillus thuringiensis into plants).

2. Reason: True. In hybridisation the whole genome of both parents is mixed, so undesirable genes also come along; in rDNA technology restriction enzymes cut out only the desired DNA fragment, which is joined to a vector by DNA ligase and inserted into the target organism.

3. The reason correctly explains the assertion, so option (c) is correct.

1. Triticale is the first man-made cereal, obtained by crossing wheat (Triticum durum) and rye (Secale cereale).

2. Its sterile F1 hybrid is made fertile by inducing polyploidy with colchicine, giving hexaploid Triticale (2n = 42).

3. This variety has higher dietary fibre and protein content.

1. IR-8 (Miracle rice) was developed by IRRI, Philippines, as a high-yielding semi-dwarf rice.

2. It was a hybrid of the high yielding variety Peta from Indonesia and the dwarf variety Dee-geo-woo-gen from China.

3. The dwarfing gene came from Dee-geo-woo-gen (DGWG).

1. Genetic engineering is the manipulation and transfer of genes from one organism to another organism.

2. The new DNA formed by joining DNA from two different sources is called recombinant DNA (rDNA).

3. Hence it is also called recombinant DNA technology.

1. Embryonic stem cells – extracted and cultured from early embryos, derived from the inner cell mass of the blastocyst; they can develop into any cell of the body.

2. Adult (somatic) stem cells – found in new born and adults; sources are amniotic fluid, umbilical cord and bone marrow; they give rise to specific cell types.

1. Genetic modification is the alteration of genes in an organism using rDNA techniques to produce desired characteristics.

2. The DNA fragment inserted into the organism is called a transgene.

3. Plants or animals expressing a modified endogenous gene or a foreign gene are called transgenic organisms, e.g. Golden Rice, Bt plants, transgenic sheep and fish.

1. Biofertilisers are living micro-organisms (e.g. Rhizobium, Azospirillum, Azotobacter, blue-green algae, mycorrhiza) applied to seed, soil or root to enrich the nutrient status of the soil.

2. They fix atmospheric nitrogen and solubilise/mobilise phosphorus and other nutrients, thus making them available to the crop plants and increasing soil fertility and yield.

3. They add organic matter, improve soil texture and the activity of useful soil microbes.

4. They are cheap, renewable and eco-friendly; unlike chemical fertilisers they leave no toxic residue and do not pollute soil and water, so they support organic farming (as advocated by Dr. G. Nammalvar).

1. Plant diseases are caused by pathogens like viruses, bacteria and fungi, and they reduce crop yield. So varieties resistant to these pathogens are bred.

2. Method: plants with the resistance character are selected and crossed (hybridisation) with high yielding varieties, and the progeny is repeatedly selected until a resistant, high yielding variety is obtained.

3. Advantage: it increases the yield and reduces the use of fungicides and bactericides.

4. Examples: Himgiri (wheat) resistant to leaf and stipe rust and hill bunt; Pusa Shubhra and Pusa Snowball K-1 (cauliflower) resistant to black rot; Pusa Komal (cowpea) resistant to bacterial blight.

1. High yielding capacity – semi-dwarf Mexican wheat varieties like Sonalika and Kalyan Sona greatly increased production.

2. Semi-dwarf and fertilizer responsive nature – the short, strong stem does not lodge and responds well to fertilizers.

3. Disease resistance and better nutritional quality – Himgiri is resistant to leaf and stipe rust and hill bunt, and Atlas 66 is a protein rich wheat variety. Sharbati Sonora, a mutant of Sonora-64, is also an improved variety.

1. Biofortification produced maize hybrids enriched with the amino acid lysine.

2. These lysine rich maize hybrids developed in India are Protina, Shakti and Rathna.

(a)

1. Somatic gene therapy: the defective gene is replaced in the somatic (body) cells of the patient.

2. Germ line gene therapy: the defective gene is replaced in the germ cells, that is, the egg and the sperm.

3. In somatic gene therapy the correction benefits only the patient and is not carried to the next generation; in germ line therapy the corrected gene would be passed on to the offspring.

4. All gene therapy conducted till date has targeted only somatic (non-reproductive) cells.

(b)

1. Undifferentiated cells (stem cells) are unspecialised mass of cells; differentiated cells are specialised cells that carry out specific functions.

2. Stem cells can divide and give rise to more stem cells by self-renewal; differentiated cells do not have this potency.

3. Stem cells can change into specialised cells by the process of differentiation; differentiated cells are already fixed in their fate.

4. Examples of differentiated cells are neurons which transmit signals, heart cells which contract to pump blood and pancreatic cells which secrete insulin.

1. Forensic use: it is widely used in crime investigation to identify the culprit, since each person's DNA sequence is unique.

2. Paternity testing: it settles disputes about parentage.

3. Research use: it helps in the study of genetic diversity of a population, evolution and speciation.

4. The technique uses Variable Number of Tandem Repeats (VNTRs) of satellite DNA as molecular markers.

1. Stem cells are undifferentiated cells that can divide and give rise to more stem cells by self-renewal.

2. They can also differentiate into specialised cells with specific functions.

3. So when cells, tissues or organs are permanently damaged or lost due to a genetic condition, disease or injury, stem cells can replace them. This treatment is called stem-cell therapy.

4. Example: in neurodegenerative disorders like Parkinson's disease and Alzheimer's disease, neuronal stem cells are used to replace the damaged or lost neurons.

1. Inbreeding is the mating of closely related animals within the same breed for about 4–6 generations; outbreeding is the breeding of unrelated animals or of two different breeds/species.

2. Inbreeding helps to accumulate superior genes and eliminate undesirable genes; outbreeding produces hybrids that are stronger and more vigorous than the parents (heterosis).

3. Continued inbreeding causes inbreeding depression – reduced fertility and productivity; outbreeding increases milk, egg and meat production and growth rate.

4. Example of inbreeding: superior males and females of the same breed mated in pairs. Example of outbreeding: male donkey × female horse gives the mule, which is stronger but sterile.

1. High yield – the variety must give more produce per unit area, like the semi-dwarf wheat varieties Sonalika and Kalyan Sona and the rice variety IR-8.

2. Better quality – improved protein, oil and mineral content through biofortification, e.g. Protina, Shakti and Rathna (lysine rich maize) and Atlas 66 (protein rich wheat).

3. Disease resistance – resistance to viruses, bacteria and fungi, e.g. Himgiri wheat (rust, hill bunt), Pusa Shubhra cauliflower (black rot), Pusa Komal cowpea (bacterial blight).

4. Insect and pest resistance – e.g. Pusa Gaurav (aphids), Pusa Sem 2 and 3 (leaf hopper, fruit borer), Pusa Sawani lady's finger (shoot and fruit borer).

5. Shorter duration of the crop and tolerance to adverse conditions such as drought and salinity (e.g. Atomita 2 rice with saline tolerance).

1. Green Revolution raised food production using high yielding varieties and modern agricultural techniques, but it depends heavily on chemical fertilizers, fungicides, bactericides and pesticides.

2. Continuous use of these chemicals pollutes the soil and water and leaves harmful residues in food, affecting human and animal health.

3. Organic farming avoids synthetic chemicals and uses natural manures, so it maintains soil fertility and keeps the environment safe.

4. Dr. G. Nammalvar, a Tamil agricultural scientist, founded the Nammalvar Ecological Foundation (Vanagam) to create public awareness about the benefits of organic farming and global food security.

1. An organism having more than two sets of chromosomes is called a polyploid; the condition is polyploidy.

2. Extra sets of chromosomes mean more genes and more DNA per cell, so cell size and cell contents increase.

3. This increase in cell size shows up as larger leaves, shoots, flowers and fruits — the gigantism seen in polyploids.

4. Examples: TV-29, a triploid tea variety, has larger shoots and drought tolerance; triploid seedless watermelon and banana; Triticale (6n) has higher dietary fibre and protein.

(i)

1. P is the beta carotene gene, which is needed for the synthesis of Vitamin A in humans.

2. Q is the rice plant, whose genome receives the transgene.

3. R is Golden Rice, the genetically modified rice that produces beta carotene.

(ii)

1. Golden Rice produces beta carotene, which the human body converts into Vitamin A.

2. Rice is the staple food of most Indians, so a Vitamin A rich rice easily reaches a large population.

3. It helps to prevent Vitamin A deficiency and the blindness and ill health caused by it, especially in children.

4. It is an example of improving the nutritional quality of a crop, which helps to fight malnutrition in India.