Molecular Biology and Genetics - Lecture Eleven : DNA structure
4 important questions on Molecular Biology and Genetics - Lecture Eleven : DNA structure
What are the components of DNA ?
A nucleotide is composed of :
- Pentose sugar : Either deoxyribose (DNA) or ribose (RNA)
- Phosphate group
- Nitrogenous nucleobase
- Purine bases (Adenine and Guanine : 2 rings
What are phosphodiester bonds in the DNA ?
- These are formed via a condensation reaction
- As H2O is a byproduct that forms alongside this bond between two nucleotides
- 3’ carbon of pentose sugar on nucleotide 1 attaches to the phosphate on nucleotide 2
- Many individual nucleotides eventually form a single polynucleotide (nucleic acid)
- The phosphates forms the backbone of nucleic acids
What is the Chargaff's Rules ?
- The number of adenine (A) nucleotides = thymine (T) in DNA nucleotides
- The number of adenine (A) nucleotides = uracil (U) in RNA molecules
- The number of guanine (G) nucleotides = cytosine (C) in both RNA and DNA nucleotides
2nd Rule :
- The composition of DNA varies between species
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What is the Watson-Crick Structural Model of DNA ?
- Antiparallel DNA Strands :
- Parallel, but in the opposite direction
- Double Helix
- Complementary Base Pairing
- Sugar-phosphate ‘backbone’ is on the outside
- Bases face inward
This model leads deciphering how the genetic code works and deciphering the mechanisms behind DNA replication.
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