Download App

Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance4 Marks
Question
Describe the molecular structure of DNA by making a labelled diagram.
✓

Answer

DNA is a long molecule. Its units are called nucleotides. Each nucleotide contains three compounds— pentose sugar, phosphoric acid and nitrogenous base
I. Pentose Sugar : It is a five carbon sugar which is called deoxyribose. There is one less oxygen molecule on carbon (See Fig.).
Image
II. Phosphoric Acid : This orthophosphoric acid is $H _3 PO _4$. In nucleic acids, phosphoric acid and pentose sugar are found in alternating order, that is, one molecule of phosphoric acid is found between two sugar molecules. Each phosphate group is $3^{\prime} C$ of one sugar and by connecting to $5^{\prime} C$ of the second sugar, it forms a phospho diester bond. The chain of nucleic acid starts from $5^{\prime} C$ and ends at $3^{\prime} C$ or starts from $3^{\prime} C$ and ends at $5^{\circ} C$.
III. Nitrogenous bases : These are of two types :
(i) Pyrimidine : One of these is a heterocyclic hexagonal ring which contains four carbons and two nitrogen. Two types of Pyrimidine—thymine (T) and cytosine (C) are found in DNA whereas RNA contains uracil (U) in place of thymine.
(ii) Purine : In this, an imidazole ring is combined with the fourth and fifth carbon of purine. Purines named Adenine (A) and Guanine (G) are found in both DNA and RNA.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "4 Marks Questions" from Molecular Basis of Inheritance→Molecular Basis of Inheritance — all question types→BIOLOGY STD 12 Science question papers→Rajasthan Board STD 12 Science question papers→Rajasthan Board question paper generator→

Similar questions

Describe the structure of human sperm.###Describe the structure of sperm with suitable diagram. Also define supermatogenesis.
→
It is commonly observed that parents feel embarrassed to discuss freely with their adolescent children about sexuality and reproduction. The result of this parental inhibition is that the children go astray sometimes.
  1. Explain the reasons that you feel are behind such embarrassment amongst some parents to freely discuss such issues with their growing children.
  2. By taking one example of a local plant and animal, how would you help these parents to overcome such inhibitions about reproduction and sexuality?
→
Explain the events upto fertilisation that occur in a flower after the pollen grain has landed on its compatible stigma.
→
find out how to distinguish between: RNA and DNA
→
'Analysis of age pyramids for human population can provide important inputs for long-term planning strategies'. Explain.
→
The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form:
  1. MALT.
  2. CMI.
  3. AIDS.
  4. NACO.
  5. HIV.
→
Explain the role of lactose as inducer in lac Operon.###What is lac operon concept? Describe its mechanism.###In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?###Define the operon and name its Constituent Genes.
→
With the help of a diagram explain the structure of DNA.
→
Draw a picture of viral replication. Write the full name of AIDS pathogen. How does hybridization occur? Explain the symptoms of AIDS in human body.
→
What is oogenesis? Give a brief account of oogenesis.
→