Nucleic Acids Flashcards
The Central Dogma: Infomation Transfer
describes the flow of genetic information in cells
DNA Replication
DNA is Replicated into DNA
Transcription
DNA is transcribed into messenger RNA (mRNA)
Translation
RNA is translated into proteins
Reverse Transcription
RNA is transcribed into cDNA
Nucleotides
have three components, they are?
- Nitrogenous Base: info
- Pentose sugar: structure
- Phosphate Group: structure
- can exist as monomers when no phosphate group attached.
- can have 1-3 phosphates
Nitrogenous Base
- purines: adenine or Guanine (contain 2 rings)
- Pyrimidines: thymine, Cytosine (or Uracil (U) in RNA) (contain 1 ring)
- contain carbon, nitrogen, and amino group (NH2)
Pentose Sugar
A 5 Carbon sugar ring
- Deoxyribose in DNA
- Ribose in RNA
- determines direction of nuclei acid
Polynucleotide Chains
- nucleotides are connected through a phosphodiester bond
- Have a phosphate group at one end (5’ end) and an OH group attached to the sugar
naming of Nuleotides
nMP - 1 phosphate
nDP - 2 phosphates
nTP - 3 phosphates
where n is the name of the nucleoside
NTPs (such as ATP) carry what?
chemical energy
cAMP and cGMP are important regulators of what?
cellular metabolism
Polymerisation:
joining nucleic acids together.
Nucleic Acids are polymers of ______
nucleotides
Nucleotides are link ___
3’ to 5’ by phosphodiester bonds
Polynucleic acid has a …
phosphate group at one end (5’ end) and a OH group attched to the sugar (3’ end)
Levels of Structure in DNA
- Primary Structure
- Secondary Strcuture
- Tertiary Structure
- Quaternary Structure
Primary Structure
the order of bases on the polynucleotide sequence (specifies genetic code)
Secondary Structure:
3D conformation of polynucleotide backbone (complementary bas pairing - denaturation/replication)
Tertiary Structure:
Supercoiling
Quaternary Structure
Interactions between DNA and proteins
H-Bonds Build Connection
- DNA is formed by two complementary antiparallel strands
- Base pairing is very specific and follows Chargaff’s rule
- Base pairing and H-bonds are v important to hold the complimentary strands
- G-C pairing is stronger than A-T
Chargaff’s Rule
[pyrimidines] = [purines] [A] = [T] [G] = [C]
Secondary Structure: the helical beauty
- Nitrogen base (steps in the ladder)-information is protected
- Pentose sugar (handrails)-structure
- Phosphate group (exposed negative side)-structure
- Two strand antiparallel
- Small groove & large groove & complete turn
- Basic connection (via H-Bonds)
Diameter is about 20 A
Tertiary Structrue: DNA Supercoling
- cellular DNA is extremely compacted (the helix is supercoiled)
- to save space
Quaternary Structure: DNA wrapping up proteins
In eukaryotes DNA is complexed with positively-charged proteins to form chromatin
- Histones (positive proteins) - Nucleosome: DNA (negative wrapped around 8 histones (positive) - 150 base pairs are in contact with the proteins - Packaged into chromosomes and safely located inside the nucleus
DNA as a Template:
- DNA helix is denatured to allow replication
- Each strand of DNA helix acts as a template for new complementary strand
- Semiconservative replication (i.e. Each daughter molecule has one old strand & one new strand)
Dependent on complementary bas pairing
DNA Replication
- Helicase: unwinds the helix to form a replication fork
- Primase: synthesises short RNA primers, complementary to the template
- DNA polymerase: reads the strand being copied and links complementary nucleotides to form a new strand
- Leading strand and lagging strand
- Leading strand is synthesised continuously from the template
- Lagging strand is synthesised with fragments (Okazaki fragments)
- DNA ligase joins Okazaki fragments and seals the gaps in the newly synthesised short strands
RNA: the other class of nucleic acids
- look at table
DNA Transcription: to get mRNA
- The information encoded in the genes is copied into a RNA molecule: messenger RNA (mRNA)
- Obtained by transcription of complementary section of DNA catalysed by RNA polymerase
- Occurs in the nucleus
- Carries the information specifying a particular protein
It varies in length
mRNA: messenger between DNA and Proteins
- It serves as genetic template, as DNA cannot leave the nucleolus
- The pre-mRNA transcripts contain non-coding RNA (introns) and coding RNA (exons)
- Mature mRNA has the coding regions
- mRNA moves to the cytoplasm
Information encoded by the mRNA is converted into an amino acid sequence
Nucelotides Functions:
- energy carries (e.g. ATP)
- Chemical messengers (e.g. cGMP)
- components of enzyme cofactors (e.g. NAD+)
no phosphate group = ?
nucleoside
Nucleoside:
The combination of a base and a sugar linked via a glycoside bond
Nucleotide:
When a phosphoric acid is esterfied to a suga (-OH) group of a nucleoside
Naming Phosphate Groups: Pyrimidine
add -idine e.g. cytidine
Naming Phosphate Groups: Purine
add -osine e.g. Adenosine
Can necleotides have more than one phosphate group attached to them?
yes up to 3
Naming of Nucleotides: 3 phosphates
nTP
where n is the name of the nucleoside
Naming of Nucleotides: 2 phosphates
nDT
where n is the name of the nucleoside
Naming of Nucleotides: 1 phosphates
nMP
where n is the name of the nucleoside
Are Nucleotides acidic or basic?
Acidic because phosphate groups create a negative charge
Nucleic acids are
polymers of nucleotides
