1.The shape of a DNA strand is called? Review of DNA 1.The shape of a DNA strand is called? 2.What three parts make up a nucleotide? 3.How many bases are there and what are their names? 4.Which bases pair together?

The shape of a DNA strand is called? Review of DNA The shape of a DNA strand is called? Double Helix

What three parts make up a nucleotide? Review of DNA What three parts make up a nucleotide? Nitrogenous base Phosphate group Simple sugar

How many bases are there and what are their names? Review of DNA How many bases are there and what are their names? Adenine Thymine Guanine Cytosine

Which bases pair together? Review of DNA Which bases pair together? Adenine &Thymine Guanine&Cytosine

DNA Replication

Replication of DNA Before a cell can divide by mitosis or meiosis, it must first make a copy of its chromosomes. The process of copying DNA is called DNA replication.

Replication of DNA DNA replication occurs during the S Phase of Interphase prior to mitosis and meiosis.

Replication of DNA During replication, each strand serves as a pattern, or template, to make a new DNA molecule. Each parent strand remains intact. Each new DNA molecule is half old and half new.

There are 3 major steps to DNA Replication

Step 1 of DNA Replication Before the DNA can be copied, the DNA helix must be unwound. This process is done by an enzyme called DNA helicase.

Step 1 of DNA Replication DNA Helicase breaks the Hydrogen bonds which “unzips” the DNA. The place where the 2 strands are separated is call the replication fork.

Step 2 of DNA Replication 2. At the replication fork, enzymes called DNA Polymerase moves along each strand of DNA and adds complimentary bases. This continues until the entire molecule has been unzipped and replicated.

Step 3 of DNA Replication 3. Once the DNA polymerase has copied the entire DNA strand, they detach. Each of the two DNA strands has 2 parts. The original half and the new half.

Result? Each new strand formed is a complement of one of the original (parent) strands. This results in two DNA molecules that are identical to the original. This occurs for ALL chromosomes.

What about Errors? Our DNA is continuously checked for errors by the DNA Polymerase.

Section 11.1 Summary – pages 281 - 287 Replication of DNA Section 11.1 Summary – pages 281 - 287

Prokaryotes vs. Eukaryotes Have circular DNA. A prokaryotes DNA is much smaller than ours, and takes much less time to replicate. Because of this, prokaryotes will have 2 replication forks, one on each side of the circle. When replication is complete, the replication forks will meet up with each other

Prokaryotes vs. Eukaryotes DNA is in one long strand. In order to get all of this copied quickly, our bodies use many replication forks, which are all spaced out along the DNA strand.