BIO 111 Lecture Notes - Lecture 14: Dna Ligase, Alkaptonuria, Chromosome
Document Summary
Dna synthesized as one long continuous molecule. Dna polymerase attaches in 5" to 3" direction. Dna polymerase can only work 5" 3". But helicase keeps exposing what will be the 3" end of the new strand. Lagging strand is made in many small fragments. Lagging strand ends up with okazaki fragments of new dna and bits of rna primers in between. Now the rna gaps have to be replaced with dna. Dna polymerase replaces rna primers with dna nucleotides. Dna ligase connects the dna okazaki fragments together. Error rate only about 1/billion bases really good! 3 errors every time a human cell copies its dna. H-bonds between a & t / g & c. Most mistakes are caught when dna polymerase proof reads . Dna polymerase backs up and removes the error. The ends of chromosomes are called telomeres. Dna replication here is a little different . Sequence (5"-gggtta-3") repeated thousands of times in a row.
