DNA & RNA Flashcards
DNA
- basis for heredity
- ability to self-replicate
central dogma
DNA->RNA->proteins
DNA structure
- basic unit: nucleotide
- nucleotide: sugar bonded to a phosphate group and a nitrogenous base
2 types of nitrogenous bases
- purines: adenine and guanine, 2-ring base
- pyrimidines: cytosine and thymine, 1-ring base
antiparallel arrangement
5’ end pointing up and the other strand has the 3’ end pointing up
Watson-Crick DNA model
- DNA is a double-strand helix with the sugar-phosphate chains on the outside and nitrogenous bases H-bonded on the inside
- T forms 2 H bonds w A
- G forms 3 H bonds w C
topoisomerase
-uncoils the DNA strands in order to replicate
DNA helicase
-breaks the H bonds b/w nitrogenous bases of each nucleotide
replication fork
opening in the DNA molecule created by DNA helicase
semiconservative replication
-original DNA strand separates and acts as a template for complementary base pairing, containing one strand from parent and a new strand
DNA polymerase
- reads parent strand and creates a complementary strand
- reads 3’->5’
- leading strand (synthesized by DNA pol) and lagging strand
Okazaki fragments
-short fragments of DNA which are synthesized discontinuously and later linked together by DNA ligase to create the lagging strand
genetic code
- A, T, C, and G
- in RNA T is replaced with U
- codons (triplets)
redundancy
most AA have more than one codon coding for them
RNA structure
-ribose sugar, uracil instead of thymine, and it is single stranded
mRNA
-carries complement of DNA sequence from nucleus to the ribosome for protein synthesis
tRNA
-brings AA coded for in the mRNA sequence to the ribosome (anticodon)
rRNA
-structural component of ribosomes, helps translate mRNA to protein
transcription
- info coded in the sequence of DNA is transcribe in mRNA that leaves the nucleus
- RNA pol binds to DNA at the promoter region, ten factors help RNA pol bind to DNA and initiate txn
- RNA pol (reads 3’->5’) adds comp nucleotides
introns
-extra sequence of nucleotides, spliced out by splisosome
exons
-nucleotides necessary to make the protein
guanine cap and poly-A tail
provide protection of RNA from enzyme degradation
translation
- mRNA codons are translated into a sequence of AA
- occurs in cytoplasm
4 stages of translation
- initiation
- elongation
- translocation
- termination
initiation
ribosome scans the mRNA until it binds to a start codon
elongation
- H bonds form b/w the mRNA codon in the A site and its comp anticodon
- peptide bond is formed b/w AA attached to tRNA in the A site and the AA attached to the tRNA in the P site
translocation
- ribosome advances 3 nucleotides along the mRNA in the 5’->3’
- tRNA in P site is expelled and the peptidyl-tRNA in the A site moves to the P site
termination
-stop codons arrives in the A site
A site
-aminoacyl-tRNA site, binds to the incoming tRNA
P site
-peptidyl-tRNA site, transferred from A then contributes it AA to the polypeptide chain
E site
-tRNA is released
