CHAPTER 8- Nucleotides and Nucleic Acid

Nucleotide Functions

-energy for (ATP)

metabolism

- enzyme cofactors (NAD+)

-signal transduction (cAMP)

- building blocks for nucleic acid

Nucleic Acid function

- storage of genetic information (DNA)

- Transmission of genetic information (mRNA)

- Processing of genetic information (ribozymes)

- Protein synthesis (tRNA and rRNA)

Pyrimidines

- One ring

- Cytosine, Uracil, Thymine

Purines

- Double ring

- Adenine and Guanine

Which nucleobase is found in both DNA and RNA

Cytosine

Which nucleobase is only found in DNA?

Thymine

Which nucleobase is only found in RNA?

Uracil

Ketone in purine structure

Guanine

NH2 in purine structure

Adenine

Phototropic Tautomer

structural isomer

Beta- N Glycosidic positions

position N1 in pyrimidines

position N4 in purines

phosphate + sugar =

backbone

Dna backbone is.....

STABLE

Rna backbone is....

UNSTABLE

in water

RNA lasts for a few years

in cells

mRNA is degraded for a few hours

DNA/RNA directionality

5' to 3'

Base pair

formed when 2 bases can H-bond with eachother

Chargaffs Rule

purines pair with pyrimidines

Watson-Crick base pairs

AT and CG

principles of DNA structure

- double helix

- reads 5' to 3'

- A -----> T (2H bonds)

- C------> G (3 H bonds)

- antiparallel

- hydrophobic surface

DNA polymerase

an enzyme that catalyzes synthesis of DNA strands

Confirmation of angle near 0 degrees

syn confirmation

Confirmation of angle near 180 degees

anti confirmation

B- form of n-glycosidic bond

physiological structure of DNA

A-form of n-glycosidic bond

dehydrated condition of DNA

Z- form of n-glycosidic bond

adopted by certain sequences (G-C rich)

5-Methylcytosine

common in eukaryotes, also found in bacteria

N6 Methyl adenosine

common in bacteria, not found in eukaryotes

RNA contains...

ribose sugar

uracil instead of thymine

mRNA

carries genetic info from the nucleus to ribosomes

tRNA

adaptor molecules which bring amino acids into the ribosome

rRNA

main part of ribosome which synthesize all proteins

Minor Nucleotides in RNA

- Inosine (I): wobble position of anticodon in tRNA, de-aminating adenosine, provides richer genetic code

- Pseudo uridine:

found widely in tRNA and rRNA

- most common in eukaryotes

- made from uridine by enzymatic Isome ration, folding of rRNA

Thermal Denaturation of DNA

high temperatures or change in pH

genetic info intact

H bonds broken:(two stands separate)

Base stack is lost:

increased UV absorption, hyperchromic effect

Factors Affecting DNA denaturation

-High G and C content increases Temperature

- Length of DNA fragment (longer DNA, increases temp)

- pH and Ionic Strength (increase salt concentration, increased temp)

Mutations

alterations in DNA sequence produce permanent changes in genetic information

Deamination

- slow reactions

-larger number of residues

Radiation-Induced Mutagenesis

UV light

Ionizing radiation

aging and carcinogens