Nucleic Acids Bio 14 DNA and RNA Flashcards
Chromosomes
Contain hereditary instruction for over 250k proteins unique to humans.
All cells except ova and sperm
Contain 23 pairs of chromosomes, 46 total.
A nucleis acids is a ________ made from monomeric units called ______.
Polymer, nucleotides
To eat “py” you need to CUT it
Py for pyrimidines include C,U,T with 1 ring structures.
Nucleotide, nucleoside components
Nucleotide : Sugar, phosphate, and N base (deoxyribose)
Nucleoside : Sugar and base (ribose)
2 position in chemical structure for nucleoside has OH, nucleotide has H.
Furanose ring
5 Carbon sugar
DNA
Helix structure. Sugar and phosphate makes up the backbone, held by H bonds. Rosalind Franklin produced a photograph which paved the way for Watson and Crick, double helix structure.
H bonds in nucleotides
A=T H bonds
C=_G H bonds
Rules of Chargraff is A amount = T amount
G amount = C amount
Double helix stabilization
H bonds and hydrophobic interactions between stacked bases
A=T, C=_G
A purine pairs with a pyrimidine
Why does purine pair always with a pyrimidine?
Limited space. Too large for two pyrimidines or two purines.
What type of bond joins one nucleotide group to another?
Phosphodiester bond
The bases along a backbone ware written
5’ to 3’ direction
DNA structure
Purines and pyrimidines are on the inside, sugar and phosphate are outside. H bonds hold helix together and define its 2 prime structure.
Increasing % of GC
Increase stability and melting point since more H bonds. A=T regions are first to melt and break.
Length of DNA vs Melting Temp.
Stability of DNA is dependent on the H bonds present. H bonds increase with length, the melting temp increases as well.
Amount of NaCl decrease, the melting temp decreases
DNA structure is highly negatively charged due to negative phosphodiester bonds (repelling each other). Positive Na+ cation shields the repelling charges, increasing stability. As NaCl conc decreases, the amount of shielding decrease and stability decreases.
Renaturation of single strands to form double strands
Occurs more rapidly when the DNA conc is increased. Complementary sequences need to find each other.
Melting temperature is reduced when Urea is added.
Urea is polar interfering with H bonds, decreasing stabilization.
Water solubility of Phosphate group, ribosyl group, and the nitrogen bases.
Ribosyl group and phosphate group are hydrophillic. Located outside our helix and are water soluble.
Purines and pyrimidines are insoluble in water (hydrophobic), located interiorly of the helix.
What technique is used to identify chromosomal material or DNA?
Feulgen stain. DNA stains reddish. Mild acid hydrolysis cleaves the molecule and reaction reveals the red.
Histones
DNA is wrapped around a protein called histones. DNA and histone = nucleosome.
Rich in + charged aa lysine and arginine and this allows tight binding to negatively charged DNA.
Nuclear DNA configurations
A) Euchromatin
B) Heterochromatin
Heterochromatin
Dark staining in electron micrographs. DNA is not actively transcribed.
Euchromatin
Eukaryotic, DNA is available for transcription. True chromatin, more dispersed and less compacted.
Hershey- Chase experiment
Concluded that DNA is not a protein and is actually genetic info. Radioactive sulfer and phosphorus labelled proteins and DNA. Which molecules entered the bacterial cell. Page DNA entered the bacteria.
Fred- Griffith Transformation Experiment
Two strains of bacteria: Pathogenic and nonpathogenic.
Mixed dead pathogen with living nonpathogenic and some became harmful. All further progeny were pathogenic. DNA is the culprit.
Avery McCarty Macleod Experiment
1944 confirming Griffith DNA genetic material. Mitochondria and chloroplasts also contain their own DNA.
RNA
single stranded, A, U ,C ,G
Ribose sugar ( lacking 2’ OH)
rRNA: physical makeup of ribosome, most abundant
mRNA: carries DNA info to ribosomes, shortest lived
tRNA: transports aa to ribosomes, lowest molecular weight
8x more RNA than DNA
Transcription
Occurs in the nucleus.
Why does alkaline conditions partially denature the helix?
Increasing the pH, ionizes some of the nucleic acid bases and the phosphate groups, thus increasing the # of negatively charged groups. This promotes unwinding of the helix to reduce charge repulsion.
