BIOL 190 Lecture Notes - Lecture 3: Okazaki Fragments, Dna Replication, Helicase

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7 Feb 2017
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Main functions of DNA
Cells use the genetic information stores in DNA in 2 ways:
1. Heredity- complete copy of genetic information physically passed from one generation
to the next during reproduction
a. DNA must be replicated (copied)
b. Copies passed to the daughter cells when a cell divides
c. DNA passed from parent to offspring during sexual reproduction
2. Control- DNA controls cell structure and function
a. DNA codes for proteins
b. Proteins in a cell determines its structure and function
c. All of the cells in an organism (human) determine the structure and function of
the organism!
The Watson and Crick model of DNA suggested a mechanism for DNA replication
A parental molecule of DNA ---------- The parental strands separate and serve as templates
------------ Two identical daughter
DNA replication is semiconservative
Each original strand is used a template
The new daughter molecules are made up of one original (old/blue) strand and one
“new” strand (gray)
DNA Helicase
Unwinds and separates the DNA strands
DNA Polymerase- protein that ensures right DNA joins together forming a covalent bond
Covalently links the free nucleotides to the 3’ end of the newly forming daughter strand
Polymerization always occurs in the 5’ to 3’ direction
DNA Primase
Adds primers to the template strand
Leading Strand- replication is continuous
Lagging Strand- replication is discontinuous
Synthesized in pieces called Okazaki fragments
Fragments are then joined together by DNA ligase
Ligate- to bind together
(think ligature)
DNA Replication
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