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Lecture

transcripted

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Department
Biology
Course Code
BIO120H1
Professor
Belinda Chang

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Lecture 2 Intro to Nucleic Acids & Proteins
Nucleic Acid Chains
1. DNA is synthesized from deoxyribonucleoside triphosphates, otherwise known as:
dNTPs things that are used to make this linear structure. 2 phosphates get
removed during this process.
2. RNA is synthesized from ribonucleoside triphosphates, or: NTPs
3. Nucleotides are linked by: phosphodiester bonds (through phosphate groups)
Base Pairing
-DNA is double stranded while RNA is single stranded in order for
replication & transmission of info contained in DNA strand, it needs to be
double-stranded. Basis of exactly how those strands together is mediated
through process called base pairing ensures that base opposite of it in
opposing strand is specific base b/c not all bases are complementary to each
other.
1. Holds DNA double helix together
2. A-T – 2 H-bonds
G-C – 3 H-bonds
H-bonds form, helping to keep 2 strands together
Strands run anti-parallel
3 forces that keep DNA together:
1. H-bonds – dipole-dipole interactions with each other
2. Van der Waals are induced dipoles (slight variation in positive &
negative charge) clouds of e- that when they come near each other
induce dipoles in each other.
3. Hydrophobic interactions tendency to avoid water stacking b/w bases
which are very hydrophobic particularly ring structure tend to like to
stack in certain way.
DNA Structure
- Info is always read 5’ to 3’ DNA is composed of 2 antiparallel
strands. Has ladder-like structure. Same info present on 1 strand is on
other b/c of complementarity of bases & this redundancy is extremely
important for preservation of info.
-DNA structure is organized into double helix ladder twists
around itself forming major groove & minor groove. Interactions with
turns of helix make DNA more stable.
www.notesolution.com
Review Qs
1. Strands in double helix are antiparallel (go in opposite direction)this means that 1 strand is 5’ 3’ while
its partner is 3 5’
2. What are 2 ends of DNA strand composed of? 5’ = P, 3’ = OH
Sequence of 2 strands are: complementary. Strands can be unzipped (reversiblecan be reannealed).
This is important for: DNA replication (making copy of DNA), protein synthesis (i.e. making RNA copy 
protein)
Unzipping Helix
1. Heating denatures double-stranded DNA by: disrupting H-bonds b/w bases (specifically those H-bonds
mediating base pairing holding 2 strands together)
2. Temp at which DNA denatures is called: TM
3. Denaturation of DNA is reversible process
Review Qs
1) Why is TM of DNA rich in G-C base pairs higher than TM of DNA rich in A-T base pairs? G-C have 3 H-
bonds; A-T have 2
2) Why do high temp organisms such as bacteria around undersea vents have G-C rich genomes? DNA would
denature
Intro to Protein Structure
Ex:
Primary (sequence)
Secondary (local folding)
Tertiary (long-range folding)
Quaternary (multimeric organization)
Supramolecular (large-scale assembly)
- AA sequence
- a-helix, B-sheet
- 3D structure
- protein assemblies
Protein Structure
1. Proteins are composed of AA
2. AA side-chain or R group is variable & determines type of AA (only part of
entire AA that variesanalogous to base in nucleotide)
3. 4 major categories of AA: basic (positively charged AA), acidic (negatively
charged), uncharged polar (1s with hydroxyl groups on them), non-polar
(hydrophobic AA)
Mutational steps b/w codons
1) What is min # of mutational steps b/w AA? - # mutations b/w codons for different AAs
2) How many mutational steps required to get from a codon for proline to one for cysteine, minimum? 2 (CCG 
UGC)
www.notesolution.com

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Description
Lecture 2 Intro to Nucleic Acids & Proteins Nucleic Acid Chains 1. DNA is synthesized from deoxyribonucleoside triphosphates, otherwise known as: dNTPs things that are used to make this linear structure. 2 phosphates get removed during this process. 2. RNA is synthesized from ribonucleoside triphosphates, or: NTPs 3. Nucleotides are linked by: phosphodiester bonds (through phosphate groups) Base Pairing - DNA is double stranded while RNA is single stranded in order for replication & transmission of info contained in DNA strand, it needs to be double-stranded. Basis of exactly how those strands together is mediated through process called base pairing ensures that base opposite of it in opposing strand is specific base bc not all bases are complementary to each other. 1. Holds DNA double helix together 2. A-T 2 H-bonds G-C 3 H-bonds H-bonds form, helping to keep 2 strands together Strands run anti-parallel 3 forces that keep DNA together: 1. H-bonds dipole-dipole interactions with each other 2. Van der Waals are induced dipoles (slight variation in positive & negative charge) clouds of e- that when they come near each other induce dipoles in each other. 3. Hydrophobic interactions tendency to avoid water stacking bw bases which are very hydrophobic particularly ring structure tend to like to stack in certain way. DNA Structure - Info is always read 5 to 3 DNA is composed of 2 antiparallel strands. Has ladder-like structure. Same info present on 1 strand is on other bc of complementarity of bases & this redundancy is extremely important for preservation of info. - DNA structure is organized into double helix ladder twists around itself forming major groove & minor groove. Interactions with turns of helix make DNA more stable. www.notesolution.com
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