DNA structure

Topics: DNA, RNA, DNA replication Pages: 1 (316 words) Published: April 9, 2014
DNA helicase -separates strands of nuclei acid, breaks H bond between nitrogenous bases., works at the replication fork -DNA PRIMASE- lays RNA primer , acts as new strand, can only add nucleotides to a free3' end , lays nucleotide with a 5' orientation -DNA POLYMERASE 3- adds nucleotides using base pair rules lcreating 2 new daughter strands, only adds to a free 3'end and lays down nucleotide with 5' orientation. Pol3 continuously synthesizes new daughter cell(leading strand) same direction as rep fork. Uses only 1 primer . Pol 3 dis continuously synthesizes lagging strand, lagging strand built in op direction of rep fork, built from parent strand with open 5', uses more that 1primer -DNA POLYMERASE1 - removes and replaces RNA primers with DNA , leaves unconnected Okazaki fragments on lagging strand -DNA LIGASE- responsible for joining Okazaki fragments

-DNA POLYMERASE2 - repairs mismatches anytime
-TELOMERE -ends of eukaryotic chromosome , genetic material they contain is useless, each time chromosome is replicate telomere is lost -TELOMERASE - enzyme that adds more telomere, activity differs during dif parts of life span, very active in young, low in somatic cells of adults, cancer cells shows increased telomerase activity TRANSCRIPTION: 2 strands , TEMPLATE STRAND used to make mRNA , only promoter( signals start of transcription) and terminator(end of transcription) are used ! -RNA POLYMERASE- adds nucleotide using base pair rules to create mRNA, no "T" in RNA "U" instead -mRNA PROCESSING- splicing- sections are removed from pre mRNA and stay in nucleus (INTRON) some mRNA sections are not removed from pre mRNA and exit the nucleus (EXON) -POLY A TAIL and 5' cap are added to prevent degradation of mRNA in cytosol headed to ribosome for TRANSLATION- read in groups of 3 nucleotides called codons , mature mRNA begins with START CODON, and ends with STOP CODON -tRNA - molecule responsible for reading code mRNA carries free amino acids to Ribosome -ANTICODON-...
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