L14 Flashcards
(45 cards)
Structure of DNA
double helix can have A, B, Z conformations DNA is a polymer of poly nucleotides, a huge polymer Right handed Major and minor grooves
Structure of RNA
polymer of polynucleotides
single strand with stem-loop
The conformational freedom of what is limited?
the glycosidic bond, ribose ring, and sugar phosphate backbone
What terms are super coiled DNA described in?
linking number, twist and writing number
What are topoisonmerases?
Used to cut one or both strands of DNA to add or remove supercoils
What does the genome comprise of?
Exons: part of the gene that gets expressed
Introns: rest of the gene
What is the central dogma of molecular biology?
DNA–transcription–> RNA —-translation–> protein
What’s the difference between nucleosides and nucleotide?
Nucleotide has a phosphate attached to it. While nucleosides are linked to sugar and pentose
What is the Chargaff’s rule?
Different organisms’ composition of bases have to be equal.
What is hybridization? What does it allow?
The pairing of two DNA or RNA strands that form non covalent duplexes.
It allows templated polymerization. The backbone is identical in each repeating unit. But the bases vary.
What do phosphodiester bonds link?
Nucleotide residues in DNA and RNA.
The H base paring provides specificity.
What carbon does the phosphodiester and glycosidic bonds stem off of?
phosphodiester (3'5') glycosidic bond (1')
What is an A DNA conformation like?
scrunched with a fatter helix
What is Z DNA like?
Forms left handed double helix
What does an RNA look like when it forms a double helix?
It looks like DNA A form.
State for each A, B and Z, if its’ condensed or not.
A is un condensed and rest is condensed.
Glycosidic bond conformation for A, B, Z
Anti, Anti and for Z, it’s Anti for pyrimidines and syn for purines
What are the physical constraints of the nucleic acid structure? How many torsion angles?
The bond rotation of the nucleotide unit.
There’s seven torsion angle that dictates the conformation, 6 sugar phosphate and 1 glycosidic bond.
What are the syn and anti conformations?
syn conformation is base rotated out
anti conformation is base rotated in
remember how bases reaches in and rotates limits the constraints that happens in the backbone
Ribose conformation: C3’ endo
5.9 A, less rotation than C 2
Ribose conformations C2’ edo
7.0 A. How much rotation available dictates the conformation that pushes inside the constraint of the DNA.
What does supercoiling help with?
It helps pack the DNA in the cell and protects it.
What does the topological tension in DNA affect?
It affects normal gene regulation.
Describe L = T +W
L= linking number: one DNA strand winds around another
T= Twist, complete rotation polynucleotide strand
W=Writing
