Q25 of 31 Page 1

Which methodology is used while sequencing the total DNA from a cell? Explain it in detail.

For sequencing the total DNA from the cell, two methods are used. These are ESTs (Expressed sequence Tags) and sequence annotation.


In ESTs method the part of DNA is transcribed into mRNA and translated into proteins. Later, it focuses on sequencing the part denoting a gene.


In sequence annotation: For sequencing in this method, the total DNA from a cell is isolated and converted into random fragments of relatively smaller sizes and cloned in suitable host using specialised vectors. The cloning results in amplification of each piece of DNA fragment.


The fragments are sequenced using automated DNA sequencers, which worked on the principle of a method developed by Fredrick Sanger for determination of amino acid sequences in proteins. These sequences were then arranged based on some overlapping regions present in them.


Specialized computer-based programmers are developed, and these sequences are subsequently annotated and assigned to each chromosome.


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24

The graph given below shows the variation in the levels of ovarian hormones during various phases of menstrual cycle:


(a) Identify ‘A’ and ‘B’.


(b) Specify the source of the hormone marked in the diagram.


(c) Reason out why A peaks before B.


(d) Compare the role of A and B.


(e) Under which condition will the level of B continue to remain high on the 28thday?

 25

Explain the process of protein synthesis from processed mRNA.

 26

Taking the example of a lake as a simple aquatic ecosystem, interpret how various functions of this ecosystem are carried out. Make a food chain that is functional in this ecosystem.

 26

(a) Colonization of a rocky terrain is a natural process. Mention the group of organisms which invade this area first. Give an example.

(b) Over the years, it has been observed that some of the lakes are disappearing due to urbanization. In absence of human interference, depict by making a flow chart, how do the successional seres progress from hydric to mesic condition.


(c) Identify the climax community of hydrarch and xerarch succession.