BIO206H5 Lecture Notes - Lecture 2: Thymidine, Ribose, Purine

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31 Oct 2015
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Bio 206: Nucleic Acids and DNA
Lecture 2
99% of DNA sequence of chimp DNA is similar and structural synteny (same order of
nucleotide) to human DNA
How do we estimate relatedness?
- used Ribosomal RNA
oit doesn’t change over time
olong memory
orRna is part of transfer system  everything has a ribosome
3 Groups
1. Bacteria
2. Archaea
3. Eukaryotes
Archaea
- look like bacteria, act like bacteria
- however more genetically related to eukaryotes
- found in unusual environments
ohot springs
ounder pressure
ohigh salt, low oxygen
oextreme habitats
Horizontal Gene transfer
- the transfer of gene from prokaryotes to eukaryotes
- endomitochondria hypothesis  prokaryote engulphed another prokaryote which
turned into mitochondria
omassive horizontal gene transfer
- prokaryotes increase gene variation
by horizontal gene transfer
Central Dogma of Molecular Biology
Flow of Information
- linear info of mRNA is transferred
into a linear amino acid chain
- a large number of different
catalytic RNA species was
discovered recently
orna both have structural roll
and catalytic roll
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DNARNAProtein
Compartmentalized in Eukaryotes
DNA: nucleus, mitochondria, chloroplasts
Genome: the total genetic information carried by a cell or organism
DNA is found in nucleus, mitochondria, and chloroplast
Ribosome in mitochondira, and chloroplast
Content of the Nucleus
Nucleoplasm
- DNA
oGenetic material
oInformation required to build an organism
- DNA associated with histones proteins
oDNA + histone protein = CHROMATIN
- Synthesis of RNA
Nucleolus
- condensed DNA (many copies)
- genetic information for ribosome synthesis
- site of ribosome synthesis
Around Nucleus, tightly inactive DNA called heterochromatin  not used to copy
Genomes size varies among organisms
Homo sapiens have around 3200x10^6 nucleotide pairs and approximately 30,000 genes
(proteins)
What determines how many proteins an organism has is determined on gene management
One gene codes for 1 protein in bacteria
However in eukaryote and higher organism one gene codes for multiple specific protein
Structure, structure, structure
- structure of DNA – predicts function, Structure of RNA, structure or proteins –
structural biology
- all of these macromolecules are POLYMERS
- large molecules synthesized from a small set of repeatedly utilized monomers
- DNA – a linear polymer of deoxyribonucleotides
- RNA – a linear polymer of ribonucleotides
Nucleotide Function
- genetic information (DNA)
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- protein synthesis (RNA)
- Energy (ATP, GTP)
- Signalling (cAMP)
- Coenzymes
Nucleotides
Composed of:
- pentose sugar (5 c) + nitrogenous base + phosphate
o2 types of 5 carbon sugars: either ribose or deoxyribose
o5 different nitrogen-containing bases (A,C,G,T/U)
ophosphate group
Nucleotide vs Nucleoside
- nucleosides lack a phosphate group
- Nucleotides are nucleosides with a phosphate group attached
- Nucleotides contain one, two, or even 3 phosphate groups linked in a chain
through phosphoanhydride bonds
- Nucleotide called adenalate
Nitrogenous Bases
Pyrimidine (single cycle)
- uracil
- cytosine
- thymine
Purine (dicycle)
- Adenine
- Guanine
hint to remember: the less complex bases
have a complex name, the most complex
bases have a simple name
Nitrogenous base numbering scheme!!!
Adenine: amino group attached on 6th
carbon
Guanine: ketone group on 6th carbon, amino
group attached to 2nd carbon
Cytosine: amino group on 4th C, ketone
group on 2nd C
Thymine: ketone group on both 2nd, and 4th
carbon
Pentose Sugar
Ribose
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