DNA IT’S WHAT YOUR MADE OF

So what is DNA made of?  DNA is made of nucleotides, which are each made up of a 5-Carbon sugar (deoxyribose), a phosphate group, and a nitrogen-containing base.  Chargaff’s Rule - relationship between nucleotides  DNA is made of nucleotides, which are each made up of a 5-Carbon sugar (deoxyribose), a phosphate group, and a nitrogen-containing base.  Chargaff’s Rule - relationship between nucleotides Adenine Guanine Cytosine Thymine

What is the structure of DNA?  DNA is arranged in a structure called a DOUBLE HELIX, which resembles a spiral staircase or twisted ladder  Watson and Crick discovered this structure based on the research of other scientists  Base-pairing explains Chargaff’s Rule, showing that hydrogen bonds hold the DNA together  DNA is arranged in a structure called a DOUBLE HELIX, which resembles a spiral staircase or twisted ladder  Watson and Crick discovered this structure based on the research of other scientists  Base-pairing explains Chargaff’s Rule, showing that hydrogen bonds hold the DNA together

DNA and Chromosomes  Simple prokaryotes have DNA with over 4million base pairs - or about 1.5 mm of DNA  A strand of human DNA is over 1meter long!  Like stuffing a 300 meter rope into a backpack  Chromatin in DNA is tightly coiled around proteins called HISTONES  Simple prokaryotes have DNA with over 4million base pairs - or about 1.5 mm of DNA  A strand of human DNA is over 1meter long!  Like stuffing a 300 meter rope into a backpack  Chromatin in DNA is tightly coiled around proteins called HISTONES

DNA Replication  Double Helix shape of DNA allows it to make copies  Eukaryotic DNA is copied at hundreds of locations - called “replication forks”  During replication, DNA splits into two strands and then produces two new, complementary strands following the rules of base pairing.  Double Helix shape of DNA allows it to make copies  Eukaryotic DNA is copied at hundreds of locations - called “replication forks”  During replication, DNA splits into two strands and then produces two new, complementary strands following the rules of base pairing.

How does Replication work?  Several enzymes are needed to complete DNA replication  DNA Helicase is the “scissor” that cuts open the DNA, making a replication fork  Primase puts down a “primer” where DNA Polymerase begins  DNA Polymerase adds bases 1 by 1, according to the original strand  Several enzymes are needed to complete DNA replication  DNA Helicase is the “scissor” that cuts open the DNA, making a replication fork  Primase puts down a “primer” where DNA Polymerase begins  DNA Polymerase adds bases 1 by 1, according to the original strand

Directional Structure of DNA  Base pair structure is non-symmetrical, resulting in 3’ end, and a 5’ end  DNA can only be replicated from 5’ to 3’  Results in formation of Okazagi Fragments  Base pair structure is non-symmetrical, resulting in 3’ end, and a 5’ end  DNA can only be replicated from 5’ to 3’  Results in formation of Okazagi Fragments

REVIEW AATGGCGAGCT TTACCGGTCGT ATACCGATTAG TACGGCTAACC AATGGCGAGCT TTACCGGTCGT ATACCGATTAG TACGGCTAACC  What is wrong with the two examples of DNA to the left?  Explain in your own words, how DNA strands are copied