DNA part 4
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The document discusses the necessity of pairing in DNA, emphasizing that DNA molecules require complementary chains for stability and function, likening this to the biological need for both male and female to produce offspring. It explains the bonding mechanics between nucleotides, detailing the types of DNA twists: B-form, A-form, and Z-form, each with varying characteristics and bonding configurations. The document highlights the structural complexity and variations in DNA arrangements, essential for understanding genetic processes.
DNA part 4
- 1. DNA part 4 Prep by : Mohamed Abdukadir kalif Mphil in Optometry
- 2. DNA chain
- 3. • In real life even alone man can not produce child , and alone women can not give birth to child without men . • So as DNA , a single molecule of DNA can not live alone it needs another molecule of DNA . • So how is single chain DNA arranges another chain of DNA ?
- 4. • To produce a child there is a need of man and woman which are different living organisms • so as the two chains of the DNA molecules , they are different from each other . • Because mostly identical things don’t attract each other except in some circumstances
- 5. • To arrange another chain of DNA • Adenine bonds with thymine in upside down way • And the bond between them is called hydrogen bonds • Adenine and thymine have two hydrogen bonds , and it is a weak bond
- 6. Adenine bond with thymine
- 7. • Guanine bonds with Cytosine in upside down way , with three hydrogen bonds , and it is a stronger bond
- 8. Guanine bond with Cytosine
- 10. • The DNA molecules are not straight , they are twisted , their nitrogenous bases are held together by hydrogen bonds , and their wall is made of phosphate and sugar , which is held together by phosphodiester bonds .
- 11. • Most of the DNA are right hand twisted • But also in some points it becomes left hand twist • So There are different forms that the DNA twist.
- 12. B-form of DNA • This is right handed twist • It is only a DNA molecule twisting with another DNA molecule • There are ten (10) pairs of nucleotides in complete 360’ degree turn • And every pair is perpendicular to the central axis
- 14. A-form of DNA • Right handed twist • It can be one molecule of DNA twisted with another molecule of RNA , or it can be DNA twisted with another DNA • There are 11 pairs of nucleotide in complete 360’ degree turn • It is slightly dehydrated , because of the more pairs of nucleotide within 360’ degree turn
- 15. Z-form of DNA • With in right handed long chain of DNA , suddenly some areas appear which are left hand twisted , this sudden left hand twist creates zigzag area , that area of DNA which has gone in to reverse twisting is called Z- FORM of DNA . • There are 12 pairs of nucleotides in complete 360’ degree turn
- 16. To be continued