DNA, Transcription and Translation

deoxyribonucleic acid

made and found in nucleus, carries cell hereditary information

nucleic acid

macromolecule with cell’s genetic blueprint and instructions for cell functions

nucleotide

monomer of nucleic acids, made of a sugar, a nitrogenous base, and at least one phosphate group

purine

nitrogenous bases with 2 carbon-nitrogen rings— adenine and guanine

pyrimidine

nitrogenous base with 1 carbon-nitrogen ring— cytosine, thymine/uracil

ribonucleic acid

single-stranded, base paired molecule involved in protein synthesis

helicase

enzyme that “unzips” DNA during replication by breaking the hydrogen bonds

lagging strand

the strand of DNA that is replicated in fragments— going away from replication fork 5’-3’

leading strand

the strand of DNA that is continuously synthesized— going towards the replication fork 5’-3’

ligase

enzyme that joins the fragments in the lagging strand by repairing the hydrogen bonds, also occasionally fixes UV/chemically damaged DNA, is always present

Okazaki fragment

DNA fragment synthesized on the lagging strand

primase

RNA primer needed for DNA to start synthesis of a new strand

replication fork

y-shaped structure formed by “replication bubble” where replication is happening

DNA replication

helicase unzips DNA, single stranded binding protein keeps the strands separated, primase begins synthesis and DNA polymerase adds nucleotides, ligase joins and fixes the synthase

single stranded binding protein

protein that binds to a separated DNA to keep the two strands from reconnecting during replication

DNA polymerization

nucleotides join together via the phosphate group and 3’ carbon— growing always in the 5’-3’ direction

phosphate and sugar

make DNA backbone

Chargaff’s rule

base pairings— A=T, G=C

Rosalind Franklin

studied x-rays of DNA to show size that was only possible if it was a double helix

watson and crick

used Chargaff and Franklin’s work to build a model of DNA

to the right

direction DNA twists

initiation

transcription factors bind onto genes and “turn on” the ones necessary for the function

RNA polymerase

unzips DNA identified by transcription factors, copies the template and adds corresponding bases without the help of any enzyme or primer

transcription process

gene initiation, elongation, termination

elongation

RNA poly builds transcript from template, only one strand of DNA is copied and only one strand of RNA is created

coding strand

the strand of DNA that is directly copied, but is identical to the resulting RNA strand because that’s just how copying works

termination

RNA poly jumps off at the “terminator” sequence in the DNA, the transcript separates and DNA rezips

transfer RNA

final RNA product used in protein production

ribosomal RNA

final RNA product used to make ribosomes

messenger RNA

RNA product that carries coding genes and needs to go through maturation before it is usedma

maturation

5’ and 3’ caps are added to transcript, introns are excised and exons bind together

intron

“junk” section of gene that is basically gibberish

exon

portion of gene with important information that will get expressed

genetic code

triplets of mRNA codons- start/stop or code for amino acids

anti-codon

found on tRNA, makes amino acid attachment site by recognizing the codon

DNA translation

initiation, elongation, and termination

initiation

first step of translation- anti-codon recognizes the start codon and brings in the amino acid

elongation

second step of translation- next codon is read, anti-codon matches amino acid, 2 tRNA are held in the protein at a time

termination

third step of translation- the stop codon is recognized, amino acid chain breaks off and the system disassembles