290-299 Flashcards
nucleotides
Protein synthesis
■ Nucleic acid synthesis
■ Signal transduction pathways
nuceltides
Composed of three basic compounds:
■ Nitrogenous base
■ Purine
■ Pyrimidine
■ Pentose sugar
■ Deoxyribose
■ Ribose
■ Phosphate group(s)
Purines
pair with pyrimidines
Adenine—Thymine/Uracil (—-H-bonds).
■ Guanine—Cytosine (—- H-bonds).
Adenine—Thymine/Uracil (two H-bonds).
■ Guanine—Cytosine (three H-bonds).
https://drive.google.com/open?id=0B8uJUY-tie8Gd25jNzZFNV93cW8
https://drive.google.com/open?id=0B8uJUY-tie8Gd0NtMG04OFZRZFk
purines
catabolize to Uric acid
antifolate and
anticancer drugs
purine
metabolic defects
Gout
Hyperuricemia
G-6-P deficiency
cat defect of purine
uracil and cytotoxine
rna bases of pyrimidine
thymine and cytosine
dna base of pyrimidine
UV light
Methotrexate
Other anticancer
drugs
metabolic defects of pyr
Rare (highly water soluble
pyr cat defect
β-Alanine
β-Amino-
pyr cat. to
https://drive.google.com/open?id=0B8uJUY-tie8GWnp1Zy1QQmtRbTA
https://drive.google.com/open?id=0B8uJUY-tie8GWnp1Zy1QQmtRbTA
NA
Extremely polar and hydrophilic.
■ The “backbone” consists of pentose sugars linked by phosphodiester
bonds at the third and fifth carbon atoms.
Nuc. acid
The two polynucleotide chains are considered antiparallel and complementary
(one chain runs in the 5′ → 3′ direction; the other runs in the
3′ → 5′ direction).
https://drive.google.com/open?id=0B8uJUY-tie8GQlowWmVpYTRacEE
https://drive.google.com/open?id=0B8uJUY-tie8GMXE2REgxOWhXWTA
Nucleolus
site of syn of rrna
Most prevalent rna
rrna
nucelus
trna mrna
Carries amino acids
from cytosol
Contains an anticodon
(complementary
to ribosomes to mRNA codons)
trna
mrna
Carries genetic code
from DNA Contains codons to ribosomes
Least prevalent RNA.
Contains codons
(complementary
to DNA template
and tRNA anticodon)
mrna
deoxyribose sugars linked together via
phosphodiester bonds.
The backbone structure of a single RNA strand. It is constant:
ribose sugars linked together via
phosphodiester bonds
nucleosome
Consists of DNA wrapped around a histone octomer.
■ Held by ionic bonds
https://drive.google.com/open?id=0B8uJUY-tie8GUEV6SXRjMDk3Q3c
https://drive.google.com/open?id=0B8uJUY-tie8GX2dMMWJQampCd1E
chromatin
Consists of nucleosomes, enzymes, gene regulatory proteins (transcription
factors), and small amounts of RNA.
Unwinds the DNA molecule
helicase
.
Secures the replication fork, where the two DNA strands
are separated into leading and lagging strands
■ Topoisomerase:
Forms new complementary strands in the 5′ → 3′
direction.
DNA polymerase:
Runs in the 3′ → 5′ direction. Synthesized continuously
Leading strand:
Runs in the 5′ → 3′ direction. Synthesized in segments
(Okazaki fragments).
Lagging strand:
Joins Okazaki fragments
DNA ligase:
Removes the nuclueotide primer
Exonuclease:
Reforms the supercoiled structure once the replication fork
has passed.
DNA gyrase:
DNA is used as a template to form RNA.
■ Occurs in the nucleus.
Rna syntesis
DNA is unwound and the replication fork is exposed.
■ RNA polymerase binds to a promoter site on the DNA strand.
rna synthesis
rna synthesis
Synthesis occurs in the 5′ → 3′ direction.
■
Addition of a 5′ cap and a 3′ poly(A) tail.
■ RNA splicing:
■ Removal of introns (noncoding segments).
■ Subsequent joining of exons (coding segments).
rna synthesis
An mRNA template is used to determine the specific amino acid sequence
for polypeptide synthesis
protein synthesis
Occurs in the cytoplasm (in ribosomes).
■ A small ribosomal subunit binds to mRNA.
protein synthesi
https://drive.google.com/open?id=0B8uJUY-tie8GNXFJaGl5TE5ZZFU
https://drive.google.com/open?id=0B8uJUY-tie8GSDI5MFdHUUcwOW8
Aminoacyl-tRNA synthetase■
: Adds each amino acid to tRNA.
The complementary anticodon of tRNA (carrying the first amino acid)
binds to the mRNA start codon
A —- ribosomal subunit attaches, forming a complete ribosome.
A large ribosomal subunit attaches, forming a complete ribosome.
Synthesis occurs in the 5′ → 3′ direction
until a stop codon is reached
https://drive.google.com/open?id=0B8uJUY-tie8GSk0takN3RllVX0U
https://drive.google.com/open?id=0B8uJUY-tie8GQ1VDSWhmUFBtWkk
Caused by mutagenic chemicals, radiation, UV light, and some viruses.
■ Due to failure of DNA repair mechanisms.
mutation
■ Missense mutation:
Results in a codon that causes an altered amino acid
sequence (eg, valine replaces glutamate causing sickle cell anemia).
Nonsense mutation:
Results in a stop codon that causes polypeptide
chain termination.
Transverse mutation:
A purine is replaced with a pyrimidine, or vice
versa (the purine–pyrimidine orientation is changed).
Transition mutation:
A purine is replaced with another purine, or a
pyrimidine is replaced with another pyrimidine (the purine–pyrimidine
orientation is not changed).
Deletion or insertion of one or two base pairs, changing the reading frame
of the DNA template and the amino acid sequence.
frameshift mut.
Amplification of the sequence of three nucleotides.
repeated mut.
Forms a complementary strand of DNA from the original RNA.
■ HIV contains only a single-stranded RNA molecule and its own reverse
transcriptase.
reverse trans.
Restriction endonucleases:
Cleave DNA at various points to allow addition
of various vectors, plasmids, cosmids, or bacteriophages
DNA ligases:
Join DNA fragments.
DNA polymerase:
Adds nucleotides.
Exonucleases:
Remove nucleotides.
Amplifies a target sequence of DNA.
■ Extremely sensitive, selective, and fast.
PCR
Used extensively in forensic medicine.
PCR
- Denaturation of the DNA sample into two strands
- Anneal primers to each strand
PCr
- Copy each strand by a heat-stable DNA polymerase
- Repeat cycle resulting in exponential amplification of sample
PCR
