DNA AND GENOMICS
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What is the primary function of Nucleic Acid?
Store and transmit genetic information
What are the 2 types of nucleic acid found in organisms?
- Deoxyribonucleic Acid DNA
- Ribonucleic Acid RNA
Nucleic acid are macromolecules made up of?
A structure of nucleotide
Difference between DNA and RNA
Hydrogen atom at Carbon Atom 2 in deoxyribose is replaced by an OH group in ribose
4 Bases categorised into?
Purines and pyrimidines
Difference between PURINES & PYRIMIDINES
Purines have 2 rings while Pyrimidines have 1 ring in terms of STRUCTURE
Pyriminidines are 1 RING
Cytosine and Uracil (RNA) and Thymine
How do nucleotides form?
Condensation Reactions [water is removed during the process] 2 molecules of H2O
Nitrogenous bases is linked to
Carbon atom 1 of pentose sugar molecule
Phosphoric acid is attached to
carbon 5 of pentose sugar molecule
What is a nucleoside?
- Nitrogenous bases + pentose sugar
- No phosphoric acid
How polynucleotides are form?
Formation of phosphodiester bond through condensation reactions!
5' end of polynucleotide ends with?
A phosphate group attached to C5 of sugar
3' end of polynucleotide ends with?
OH group C3 of sugar
Process of formation of polynucleotide
What is the structure of DNA?
2 polynucleotide chains twisted around each other to form a double helix structure
How do the 2 strands run?
Anti parallel - opposite direction
How is it held together?
- Hydrogen bonds between nitrogenous base pairs of opposite strands.
- Purine & Pyrimidine will always pair up
- Complementary Base Pairing
Adenine and thymine forms how many hydrogen bonds?
Cytosine and Guanine how many H bonds?
Ratio of A to T and C to G
1 : 1
1 complete turn of DNA double helix
- 10 base pairs
- Sugar phosphate backbone outside
- Nitrogenous bases occupy centre of molecule
Packing of DNA
Most DNA wound around outside of grps of 8 histone protein molecules form nucleosomes
- Remainder DNA (linker) joins adjacent nucleosomes
- Nucleosomes and linkers > chromatin fibre
Chromatin fibre coils around ITSELF form solenoid
6 nucleosomes in 1 turn of solenoid
Coiling of solenoid gives rise to chromatin
Condensation of chromatin > chromosome
DNA REPLICATION wrt to base pair & H bond
Double helical structure enables semi-conservative replication to occur
During replication, 2 strands can unwind and separate
Each strand act as template to which complementary set of nucleotides will attach by base pairing and hydrogen bonding
Each original DNA molecule give rise to 2 copies of DNA with identical structure and base seq
intact complementary strand can be used as template to guide repair
repair ensure integrity of base seq of DNA molecule remains intact
Stability of DNA molecule
Bases held together by H bonds together with hydrophobic interactions btw stacked bases, stabilize structure
- Adjacent nucleotides held together by strong covalent phosphodiester bond
- Integrity of DNA base seq maintained
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