DNA Replication
What is DNA Replication? The copying of DNA before a cell divides so that new cells receive all the important genetic information. Each strand in the double helix has all the information needed to reconstruct the other half because of BASE PAIRING
DNA Structure Review Nucleotides contain: 5-carbon sugar Phosphate group Nitrogenous base (A, T, G, C) Nucleotides form covalent bonds together to form a chain or strand of nucleotides (sugar of one nucleotide bonds to phosphate group of another) Two strands bond together by HYDROGEN bonding between the nitrogenous bases to form a DNA molecule/ double helix
STEP 1 Step 1: DNA helicase “unzips” or opens up the two strands of DNA. The strands from the original DNA molecule are called “parental strands”
STEP 2 Step 2: A new strand is formed by adding new nucleotides one at a time. The nitrogenous base is selected by following the rules of BASE PAIRING DNA Polymerase forms new covalent bonds between the sugar molecule of one nucleotide and the phosphate group of another.
Step 2 con’t DNA polymerase also “proofreads” as it goes to make sure the right base is being added If the base on the old strand is Adenine then Thymine is added to the new strand. If the base on the old strand is Guanine then Cytosine is added to the new strand. If the base on the old strand is Thymine then Adenine is added to the new strand. If the base on the old strand is Cytosine then Guanine is added to the new strand.
Sequence Practice AGTCTCG will become ______________ GCGTCGCA will become_____________ ATCATCGA will become______________ The sequence on the old “parental strand” is used to build the new string The end result is TWO identical DNA molecules Each of the two DNA molecules has one ORIGINAL strand and one NEW strand.
Step 3 The ends of the DNA molecules are called TELOMERES They are hard to replicate. TELOMERASE adds short, repeated DNA sequences to the telomeres and helps prevent genes from being lost or damaged during replication.
Watch: https://www.youtube.com/watch?v=JZXT2uOcD2w