DNA & RNA Flashcards
Nucleotides consist of three elements
Nucleobase Deoxyribose sugar Phosphate group(s)
What is a nucleoside?
Is the nucleobase plus the deoxyribose sugar (i.e. without the phosphate).
Difference between nuceleotides and nucleocides?
Nucleotides have a phosphate group.
DNA is turned into RNA What is this called?
Transcription
RNA is turned into proteins What is this called?
Translation
Transfer RNA Ribosomal RNA What happens?
Transcribed from genes but used to translate mRNA into proteins
What is Pyrimidine?
Nitrogen containing aromatic ring
What is Purine?
Pyrimidine ring fused to imidazole ring
What nucleobase is this?
Purine
What nucleobase is this?
Pyrimidine
Types of Nucleobases
Purines
Adenine
Guanine
What nucelobase is this?
Adenine
What nucleobase is this?
Guanine
What nucleobase is this?
Cytosine
What nucleobase is this?
Thymine
Nucleosides and Deoxyribose
Deoxyribose binds to the nucelobase on a nitrogen atom of the pyrimidine or imidazole (for purine) ring
What is this nucleoside?
Deoxyribose
What is this nucleoside?
D-ribose
What is this nucleoside?
Adenosine
What is this nucleoside?
Guanosine
What is this nucleoside?
Cytidine
What are nucleotides?
Nucleotides are the building blocks of nucleic acids
What is this nucleoside?
Thymidine
Where does the Phosphate group bind?
It binds to the 5’ position of the deosyribose group.
Additional phosphate groups bind to existing phosphate groups.
e.g. Adenosine monophosphate
Other functions of Nucleotides
ATIP > GTP > UTP / CTP
Used for intracellular energy & metabolism
Other functions of Nucleotides
ATP & GTP
Intracellular signalling
Other functions of Nucleotides
ATP
Intracellular signalling
Other functions of Nucleotides
Adenosine
Also a transmitted in the brain and CVS
Sleep / wake (e.g. coffee)
Vasodilator
Antiarrhymthic for heart
Basics of DNA
Core nuclear material eukaryotes
Deoxyribose - missing the 2’ -OH group on the ribose group
“Double helix” conformation for polymer
Phosphodiester bond
Nucleobase H-bonds
Type?
Guanosine pairs with cytosine
3 H-bonds
*H = hydrogen
Nucleobase H-bonds
Type?`
Adenosine pairs with thymidine
2-H bonds
What is the structure of DNA?
- sugar phosphate backbone
- Nucleobase pairs linked
- Hydrophobic bases on inside
- Antiparallel strands
- Read from 5’ - 3’
DNA helix structure
Anti-parallel double helix
3.4nm per turn, 2nm wide
Glycosidic bonds of nucleobase and deoxyribose not at 90 degrees creates “major” and “minor” grooves.
Easier for proteins and other molecules to access DNA through major groove.
What are some intercalating agents?
Hydrophobic heterocyclic ring molecules - resemble ring structure of base pairs.
Distort DNA double helix and interfere with transcription
Acridine orange, ethidium bromide - flourescent staining of DNA
Actinomuin D - inteferes with DNA replication. Cancer chemotherapy (also quite toxic)
What is supercoiling of DNA?
Total length of human DNA molecule = 3m
DNA must be “wound” - can strain the DNA helix
Negative supercoiling relaxes DNA (and increases exposure to polymerases and transcription factors.)
Topoisomerase I and II: cleave DNA, twist strands round and reanneal.
Supercoiling and histones
What are histones?
any of a group of basic proteins found in chromatin.
What is a chromatin?
the material of which the chromosomes of organisms other than bacteria (i.e. eukaryotes) are composed, consisting of protein, RNA, and DNA.
Denaturing DNA
Strands seperated by splitting H-bonds
pH: spontaneous denaturing outside pH 2.3 - 11.5
Heat (~60 degrees)
Ionic strength
Can renature if restored through “annealing”
Structure of RNA
Single stranded polyribonucleotide. Uridine not thymidine.
~30-50% of residues form intrastrand H-bonds
Also helical
2’ hydroxyl group attached to ribose group - less stable
Shorter lifespan (~30 minutes)
RNA tertiary structure
Complex tertiary structure is vital for function
What is transcription?
First step of gene expression.
RNA is transcribed from DNA by RNA.
Polymerase complex
Occurs in the nucleus
What is translation?
Second step of gene expression.
mRNA is translated into proteins by ribosomes.
Occurs in cytosol / endoplasmic reticulum
Example of DNA transcription
New proteins created from 5’ end to 3’
Translation of ribosomes
Protein / RNA complex with numerous different individual proteins and rRNA units.
tRNA matches amino acid to nucleotide triplet and ribosome catalyses peptide bond formation.
