How to draw DNA

The DNA has twisted ladder or double helical structure. According to Watson and Crick DNA molecule consists of two polynucleotide chains wrapped helically around each other, with the sugar- phosphate chain on the outside forming ribbon-like backbone of double helix. Purines and pyrimidines on the inside of the helix projecting between two sugar phosphate backbones as transverse bars. The two polynucleotide strands are held together by hydrogen bonds between specific pairs of Purines and Pyrimidines.  Now let's see how to draw DNA accurately.

 1.Draw two vertical parallel lines as shown with pencil.

2. Draw a twisted wave touching two lines on either sides.

3. Draw another wavy curve as shown. Start the second curve  a bit near the first curve to get proper grooves of DNA.

4. Make ribbon shape on  the strands as shown. Make sure the curves you draw end at correct points as shown.

5.Draw ribbon shape on other strands too, let the two strands cross each other for now.

6. Erase the appropriate lines at crossing point such that one strand goes up at one point and goes down at next point.

 Draw transverse bars four per turn at equal distance as shown.

Label the minor goove and major grooves and other details as shown.

Continued- The hydrogen bonds between purines and pyrimidines aere such that adenine can bond only to thymine by two hydrogen bonds, and guanine can bond only to cytosine by three hydrogen bonds. The two strands urn anti-prallely that is, one strand has phosphodiester linkage in 3' to 5' direction, while other strand has phosphodiester linkage in reverse 5' to 3' direction. Both, strands remain separated by 20 Armstrong units. The coiling of double helix is right handed and a complete turn occurs every 34 Armstrongs. The helix has two external grooves, a deep wide one called Major groove and a shallow narrow one called minor groove.

How to draw internal structure of ear

Ear is the auditory sense organ and also helps in maintaining body equilibrium. Human ear is divided in to External, Middle and Internal ear.External ear consists of a flap like structure called Pinna. It leads to auditory canal. The pinna is crumpled and is made up of cartilage. Middle ear plays an important role in amplifying the vibrations received on the ear drum. The chain of three bones Malleus, Incus and Stapes helps in amplification of sound.

1. Draw the out line of the ear as well as internal ear as shown.

2. Now focus on drawing Ear drum and three bones Malleus, Incus and stapes as shown.

3.Draw the Cochlea and three semicircular canals as shown.

4. Give double line for Auditory canal and Eustachian tube.

5. Put lot of neat dots around to represent the bone

of the skull.

6. Label the parts neatly as shown.


cont:-Internal ear consists of bony labyrinth enclosing membranous labyrinth which consists of Vestibule, three semicircular canals and Cochlea. Cochlea is a spiral shaped structure. It has three paralled tubes called Scala vesibuli, Scala media and Scala tymphani. Two individual nerves arise, one from vestibule and another from cochlea.

How to draw and label the tongue

Tongue is made up of muscles. It contains about ten thousand taste buds. The taste buds are located in wall of the papillae.Like smell, taste is also a sense based on identifying chemicals in food and the texture. The sense of taste and smell have a close and cooperative working relationship. The sense of taste 'Gustation' involves qualities of Sweet, sour, bitter and salty. Umami is the savory flavor found in protein rich foods such as meat, seafood and cheese.It is associated with Monosodium glutamate(MSG) also called huching, often used in Asian cuisine.  Now, let's  draw.

1. Draw out line of tongue as shown.

2. Draw line in the middle  and above as shown.

3. Draw Papillae of different forms on tongue as shown.

4.Label the parts neatly.

Cont:-The taste receptors cells, located in the taste buds on the top and side of the tongue, sample flavours from food and drink as they come into contact with surface of tongue. These taste receptors cluster in small mucous membrane projections called 'Papillae'. Each is sensitive to molecules of a particular type.The flake like structures on tongue are called Filiform papillae, the roundish ones at the back of the tongue are vallate papillae, the bump like structures on sides of tongue are Foliate papillae. Taste buds are present in all these papillae except the Filiform papillae. Each taste bud has a cavity with a pore called taste pore. The epithelial cells, surrounding the taste buds form the taste cells or the receptors. The receptors cells are situated in the cavity. Each receptor connects to the nerve fibre. All the nerve fibres connect to main nerves that carry impulses to the brain.