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DNA structure

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Topics: DNA, RNA, DNA replication
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- 3 nucleotides opposite of the codons on mRNA

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