ï»¿ Describe Watson and Crick model of DNA. from Biology Biomolecules Class 11 Assam Board

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Describe Watson and Crick model of DNA.

Watson and Crick proposed the model of DNA in 1953.

According to Watson and Crick model of DNA :

1. The Double Helix consists of two polynucleotide chains, which are coiled like a rope in helical (spiral) fashion.

2. The two strands of polynucleotides are  run in the opposite direction and are antiparallel.

3. The backbone is formed by the sugar-phosphate-sugar chain.

4. The nitrogen bases lie perpendicular to this
backbone but face inside.

5. A always pairs with T and G pairs with C. A and T are joined by two hydrogen bonds while the G and C pair have three bonds.

6. A base pair represents each step of ascent of the spiral. At each step the strand turns 36$°$.

7. There are ten base pairs in a complete turn which has ten steps.

8. The pitch is 34Å. the rise per base pair is 3.4Å.

The Watson-Crick model of DNA.

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What is the percentage of nucleic acids in cells ?

5 - 7 percent
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What are major elements of a cell ?

Carbon, hydrogen, oxygen and nitrogen are the major elements of a cell.
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Name one monosaccharide which provides energy ?

Glucose
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What is the general formula of carbohydrates ?

The carbohydrate has a general formula - CnH2nOn Or (CH2O)n.
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Give the names of two monosaccharide sugars.

Fructose and glucose are two monosaccharides
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