What background information did Watson and Crick had with them for developing a model of DNA? What was their own contribution?

Describe Watson and Crick double helical model of DNA.

Give a brief account of Watson and Crick model of DNA.

What are drawbacks of Rutherford’s atomic model ? How did Bohr remove these ?

A man who had a plot in the shape of a parallelogram divided it into three equal parts and gave one-thrid part ot his son which again was in the shape of a parallelogram. The son seeing that there was no school in the village ecides to open a school there. Answer the following questions: Show how could this decision of the man be implemented. What part did the son get? Explain with figure.

Draw the graphs for the following tables of values , with suitable scales on the axes . Distance travelled by a car . (i) How much distance did the car cover during the period 7 : 30 a .m. To 8 a.m.? (ii) What was the time when the car had covered a distance of 100 km since it start ?

Who amongst the following scientists had no contribution in the development of the double helix model for the structure of DNA?

How do you prepare your own herbarium sheets? What are the different tools you carry with you while collecting plants for the preparation of a herbarium? What information should a preserved plant material on the herbarium sheet provide for taxonomical studies?