Lecture 10- DNA & RNA Flashcards
Griffith’s transforming principle
DNA (not proteins) can transform the properties of cells
Shows chemical nature of genes
Evidence for DNA structure
X-ray diffraction-DNA is helical with repeated units
Chargaff’s laws- total pyrimidines = total purines
Pyrimidines
Single ring structure
Cytosine
Thymine
Purines
Doine nitrogenous ring structure
Adenine
Guanine
Bonds between cytosine and guanine
3 hydrogen bonds
Bonds between adenine and thymine
2 hydrogen bonds
Pentose sugar in DNA
Deoxyribose
Pentose sugar in RNA
Ribose
Nucleoside
Sugar + base
Nucleotide
Sugar + base + phosphate
Features of 3’ and 5’ prime ends
3’ hydroxyl end- free hydroxyl group
5’ phosphate end- free phosphate group not involved in forming bond with another nucleotide
Space filling model
Phosphodiester backbone (sugars linked by phosphate groups)
Bases stacked in planar arrangement running through central of DNA
DNA is a right handed helix
B form of DNA
Standard form of DNA
Large major groove
Narrow minor groove
A form of DNA
Similar to B but squashed down form
Smaller distance between bases
Larger helix diameter
Z form of DNA
Left handed help that zig zags rather than coils
Found in vitro
Narrow diameter
the DNA double helix can denature and …. depending on temperature
Renature
Structure of RNA
Single stranded molecule
Contain uracil not thymine
Ribose sugar
mRNA
Messenger RNA- copied from DNA and used to make protein
rRNA
Ribosomal RNA
Functional RNA component of ribosome
tRNA
Transfer RNA
Involved in process of translation
Brings amino acids to ribosome during translation
Structure of tRNA
Single stranded but folds up on itself to form 3d structures
Base pairing between part of the molecule forms stem and loop structures
