Biology:2018:CBSE: (Outside Delhi): Set III

Cytokines are the small proteins that are released by some cells of the immune system. These cells activate the cellular components of innate and specific immunity like macrophage, B and T lymphocytes, mast cell etc. Some cytokines like interferons that are released by virus infected cells protect non-infected cells from further viral infection.

The dual purpose served by Deoxyribonucleoside triphosphates in polymerization are:

i. It acts as substrate

ii. It also provides energy to drive DNA polymerization by breaking phosphoanhydride bond

(a) Ramapithecus and Dryopithecus

(b) Australopithecus

A proinsulin consists of three chains polypeptide A, polypeptide B and polypeptide C.  The polypeptide chain A and B are linked together by disulphide bond. During maturation, polypeptide C chain is removed this converts the proinsulin into mature insulin.

Dengue and Chikunguniya are the disease whose spread can be controlled by the eradication of Aedes mosquitoes.

The treatment is done in four stages:

1. At first stage, physical impurities are removed by the process of sedimentation and filterationby using bar screens and grit separators.
2. From the primary clarifier water is then pumped to the oxidation ponds, where microorganisms naturally remove up to 50% of the biochemical oxygen demand (BOD).
3. After secondary treatment, water is then chlorinated and dechlorinated before going to enhancement marshes.
4. In enhancement marshes, appropriate plants, algae, fungi and bacteria help in neutralizing, absorbing and assimilating the pollutants.
5. The water is then either discharged into Humboldt Bay or used in the enhancement marshes to continue the cycle.

(a) Nostocand Anabaena are the two microbes that can enrich the soil with nitrogen.

(b) Leguminous plants have nodules on their roots. These nodules contain nitrogen fixing bacteria Rhizobium. These bacteria fix the atmospheric nitrogen directly into the soil. Since these plants contain all the necessary components required for nitrogen fixation these crops do not require any enrichment of the soil.

The procedures that ensure retention of the desired characteristics repeatedly in large populations of future generations of the tomato crop are micropropagation and inbreeding.

Micropropagation is a technique in which plant cell is multiplied in in-vitro condition to regenerate a whole plant.

In this technique, the part of plant that is used to generate whole plant is called an explant. The explant is grown in laboratory conditions using special nutrient media. The progenies obtained by this process are genetically identical to the parent. Thus with the help of micropropagation, thousands of plants identical to parent plant can be produced in short period of time.

In inbreeding process, closely related species are mated. In this method also, the genetic composition of progenies remain similar to parent plant.

(a) Heroin drug is obtained from Papaversomniferum, commonly known as poppy plant.

(b) The effects of heroin on the human body are:
i. It leads to slow heartbeat and cause vomiting, nausea etc.

ii. It also affects the functioning of the brain.

Hardy-Weinberg states that in the absence of disturbances like mutation, the frequency of occurrence of alleles of a gene in a population remain constant.

This principle can be understood by a mathematical equation called Hardy-Weinberg equation.

For example a gene has two alleles A and a in a population. If p is the frequency of occurrence of dominant allele A and q is the frequency of occurrence of dominant allele a. Then the genotype frequency in the offsprings can be represented as:

(p+q)²= p² +2pq+ q² =1