Overpopulation can exhaust natural resources and create severe conplication for survival, socio-economic problems, pollution, etc

At stage ( 1) meiosis occurs.

Mendel satisfied himself that each of the fourteen varieties were true breeding. The seeds of white flowered plants produced only white-flowered plants.It was further confirmed by allowing successive generations of each variety to self-pollinate to eliminate any form of the trait.The true breeding plants thus formed were taken as parents and represented generation.

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'.

Zygote Intra Fallopian Transfer (ZIFT) is a boon to the
couple where the female cannot conceive naturally.
In this method, fertilisation is carried out in vitro (in the laboratory conditions) and the zygote or early embryo, so formed (with upto 8-celled blastomeres) is transferred into the Fallopian tube.

Government of India legalised MTP in 1971 with some strict conditions to avoid its misuse, especially to check indiscriminate and illegal female foeticides, which are reported to be high in India. Various factors that lead to MTPs are
(i) To get rid of unwanted pregnancies due to casual unprotected intercourse or failure of the contraceptive used during coitus or rapes.
(ii) In cases where continuation of pregnancy is harmful to either foetus, mother or even both.

1. Species of Lepidoptera, Dipiera, Coleoptera, etc. The cry gene of B.thuringiensis was found to express proteinaceous toxin (Bt-toxin) inside the bacterial cells.When specific insects ingest the toxin, they are killed. The toxin denatures the epithelium of gut by creating many holes at alkaline pH (7.5- 8).
2. The cry genes expressing Bt-toxin were isolated from B. thuringiensis and incorporated into crop plants like cotton. This brings about the control of cotton bollworms.
3. In India Bt-cotton was permitted to sow at large scale in fields.

(a) Axial position - Due to Principle of Dominance

(c)  \(\overset { 1/4 }{ Axial } \quad \quad \overset { 1/4 }{ Axial } \quad \quad \quad \overset { 1/4 }{ Terminal } \)
Phenotypic ratio-Axial: Terminal :: 3 : 1
Genotypic ratio-1: 2 : 1
Homozygous axial (AA) = 1/4
Heterozygous axial (Aa) = 1/2
Homozygous terminal (aa) =1/4

A - Restriction  endonuclease
B - Agarose
C - Nylon/Nitrocellulose
D - VNTR
E - Hybridisation
F - Autoradiography

The three microbes that can be chosen for organic farming are:
(i) Rhizobium The nodules on the roots of leguminous plants are formed by the symbiotic association of Rhizobium bacteria.These bacteria fix atmospheric nitrogen into organic forms, which is used by the plants as nutrient.
(ii) Mycorrhiza Fungi from symbiotic association with plants called mycorrhiza. The fungal symbiont absorbs phosphrous from soil and passes it to the plant. Such plant shows resistance to root-borne pathogens, tolerance to salinity and drought and overall increase in plant growth and development.
(iii) Anabaena It is a cyanobacteria that is used as a biofertiliser. It fixes atmospheric nitrogen.

Yes,  we agree. As the gene flow occurs through geographical barriers over generations, by studying specific allelic frequencies in various populations of the world, we can predict the human migratory patterns in pre-historic and historic era.
There have been projects undertaken such as human genographics project. Which uses data from studies on specific genes/chromosomes/mitochondrial DNA to trade the evolutionary history and migratory patterns of humans.

(a) The cancer causing viruses,called oncogenic viruses,heve genes called viral oncogenes.when these genes that have entered our body cells are activated under certain conditions,could lead to oncogenic transformation of cells,i.e.cancer is caused.
(b) When the cells of a (benign) tumour separate,reach distant sites through body fluids and get lodged there and start new tumour there,it is called malignant.
These cells damage the surrounding normal tissues.
They compete with the normal cells and starve them of vital nutrients. 

1. After entering the body of a person,the virus enters the macrophages.
2. The viral genome (RNA) undergoes replication and reverse transcription  to become viral DNA with the help of reverse transcriptase.
3. The viral DNA gets incorporated into the DNA of the cells and directs these cells to produce virus particles.
4. The macrophages function as HIV factory and produce a number of HIV particles.
5. These HIV particles move out of macrophages and infect the helper T-lymphocytes and replicant to produce progeny viruses.
6. The progeny viruses released in the blood attack new helper T- cells.
7. This process is repeated and there is a progressive decrease in the number of helper T-cells. 

(i) O⁺ blood group contains antigen for Rh factor. Rh^- blood lacks the antigen, so if the two blood mix, it will cause clotting resulting in death of the patient.
(ii) Multiple alleles.
(iii) Sunny's sister shows understanding of science and Ahmed believes in helping a person in need without thinking about which religion or caste he belongs to.

(i) These are the substances used during transplant which suppress the immune system of the recipient so that the transplanted organ is not rejected due to incompatibility between donor and recipient.
(ii) Cyclosporin A; Trichoderma (fungus)
(iii) Doctor educated the patient's wife and removed her doubts.

(b) Spermatogenesis starts at the age of puberty due to significant increase in the secretion of gonadotrophins releasing hormone. It acts on pituitary gland to bring release of gonadotrophin. Oogenesis is initiated during embryonic development stages.
(c) Spermatogenesis is completed in tests. Oogenesis is completed in the fallopian tube at the time of fertilization.

(i) (c)
(ii) (b)
(iii) (c)
(iv) (b)
(v) (c)

(a) It is an autosomal recessive trait.
(i) The trait that is hidden in the parents (generation 1) has appeared in the daughter (generation II).
(b) (i)  Parents - Mother Aa, Father Aa
(ii) Son (generation II) - Aa.
(c) First grand daughter - Aa.

(a) X is luteinizing hormone (LH).
Y is follicle-stimulating hormone (FSH).
(b) Functions of X
(i) The LH-surge causes rupture of Graafian follicle and release of ovum, in the process, called ovulation.
(ii) It influences the formation of corpus luteum from the remaining parts of the Graafian follicle and secretion of progesterone from it.
Functions of Y
 (i) It stimulates the growth of a primary follicleinto a Graafian follicle and thus, influences oogenesis.
(ii) It stimulates the cells of the developing follicle to secrete estrogens.

(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
Explanation:
There is rapid decline in Infant Mortality Rate (IMR) and Maternal Mortality Rate (MMR) The recent World Bank data puts the MMR for India reported in 2015 at 174 per 100, 000 live births, which is a significant decline from the 215 figure that was reported in 2010.

(d): The female secondary sexual characters are developed by estrogen. Estrogens are steroid hormones secreted by growing ovarian follicles. This hormone is responsible for the development of female secondary sexual and accessory characters. In humans, it is also formed in the adrenal cortex, testis and fetoplacental unit.
Gonadotrophic hormones (LH and FSH) are secreted by the anterior lobe of pituitary gland. LH is responsible for ovulation and transforms Graafian follicle into corpus luteum and FSH stimulates spermatogenesis, maturation of Graafian follicle and secretion of estrogen in ovaries.