BSC-2010 Lecture Notes - Lecture 4: Long Non-Coding Rna, Messenger Rna, Microrna

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29 Nov 2016
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Molecular Genetics - DNA and RNA Structure
Nucleic acid structure
DNA - deoxyribonucleic acid
RNA - ribonucleic acid
mRNA - messenger RNA (information used by ribosomes to make proteins)
Non-coding RNAs:
rRNA - ribosomal RNA (structural RNAs that make up ribosomes)
tRNA - transfer RNA (match info in mRNA to particular amino acid)
siRNA - small inhibitory RNA
miRNA - micro RNA
lncRNA - long non-coding RNA
etc (snRNA, snoRNA, piRNA, …)
Polynucleotide - both DNA and RNA are polymers of nucleotides (biological macromolecule)
Sugar-phosphate backbones are covalently bonded to each other, nitrogenous bases are
non-covalently bonded (H-bond) to each other
DNA structure:
Thymine (T), adenine (A), cytosine (C), guanine (G)
Sugar-phosphate backbone & nitrogenous base
3’ end & 5’ end
Highly anionic character (negative charge)
Humans have approximately 20,000-25,000 protein-coding genes (DNA sequences that code
for protein) in their genome
* Humans have 3 billion base pairs in 23 chromosome pairs
Both DNA and RNA have linear structure of sugar-phosphate group & nitrogenous bases
attached (A, G, C in both)
Distinguishing features:
Sugars
DNA - deoxyribose (2 hydrogens attached to 2 carbon) [missing 1 oxygen]
RNA - ribose (1 hydroxyl & 1 hydrogen attached to 2 carbon)
Nitrogenous bases
DNA - thymine (T)
RNA - uracil (U)
DNA double helix
Non-covalent linkages between nitrogenous bases (A-T, G-C)
Complementary sugar-phosphate backbones have opposite polarity (go in opposite
directions)
“Anti-parallel”
Double helix is “right handed”
Pyrimidines - C, T, U
Purines - A, G
Pyrimidine & purine always H-bonded together
A + T - 2 hydrogen bonds
G + C - 3 hydrogen bonds (stronger)
“GC content” of DNA affects stability of binding of complementary strands
Takes more energy to separate GC’s than AT’s
Phosphorous is abundant in nucleic acids but not in proteins
Sulfur is present in proteins (cystine) but not in nucleic acids
Hersey-Chase experiment proved that genetic material is carried in DNA
Information flow in a cell:
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