Almost everything you need to know about DNA

Deoxyribonucleic Acid Also known as DNA Strands of DNA are called chromatin Genes are the blueprint for all of the proteins are body makes

What is DNA made of? The backbone of the ladder is made up of: Sugar Phosphate

Nucleotides The middle of the ladder is made up of only 4 nucleotides or bases! These code for ALL LIFE!!! -adenine (A) -guanine (G) -cytosine (C) -thymine (T)

A always goes with T Adenine ALWAYS goes with Thymine This is the only way they fit in the ladder!

G always goes with C Guanine always goes with cytosine It’s the only way they will fit in the ladder!

Backbone is ANTIPARALLEL DNA has a 3’ end and a 5’ end (this is based on the carbon in the ribose sugar) Each parent strand is opposite, therefore, they are antiparallel

Nucleic acid pairs are called BASE PAIRS

DNA is stored in CHROMATIN One molecule of DNA is stored in the nucleus as long strands of CHROMATIN When a cell wants to divide into two cells, it must condense its chromatin

Condensed chromatin makes CHROMOSOMES When all of the DNA has finally turned into chromosomes, the chromosomes copy themselves, and then divide into two cells.

Cell Cycle Every cell in your body goes through a cell cycle. Its like its own life mini life cycle. What kinds of cells have to multiply throughout your life? What kinds of cells usually stop multiplying as an adult?

Cell Cycle The life of a cell has 3 stages called the cell cycle: 1. Interphase 2. Mitosis 3. Cytokinesis

Cell Cycle One cell divides, and makes 2! TWINS!!!!

1. Interphase It’s the longest phase It is when the cells are carrying out functions to survive, and preparing for the second step, mitosis.

Interphase DNA replicates itself in interphase! We have 3,000,000,000 nucleotide base pairs in our DNA that needs to be replicated! How does DNA replicate?

DNA Replication 1. The strands unwind 2. Each strand is a “parent” strand 3. A new daughter strand attaches to each parent strand. 4. You now have two copies of the DNA in one cell!

DNA Replicated!-We now have double the amount of chromosomes in the nucleus!

But Exactly How Does DNA Replicate? DNA has genes that code for unwinding These are called “Origins” Where the DNA unwinds is the “Replication Fork” The turquoise strand is the parent strand. The lime green strands are the new daughter strands.

Helicase This is the enzyme that causes the parent strands of DNA to separate, so replication can occur.

DNA Polymerase Anything that ends in “ase” is an enzyme! DNA Polymerase is an enzyme that adds new nucleotide bases to the parent strands.

DNA Polymerase Adds nucleotides, and will also make corrections when wrong nucleotides are added! Is highly conserved in evolution! All organisms have very similar DNA polymerase.

DNA Polymerase It reads DNA from the 3’ end to the 5’end

Leading Strand Reads from 3’ to 5’ Therefore, nucleotides are added 5’ to 3’ Its so easy and everyone is happy DNA is replicated in one continuous fashion!

Lagging Strand

Lagging Strand DNA Polymerase can only replicate small chunks at a time, since DNA HAS to be read 3’ to 5’ These small chunks are called Okazaki fragments

Empty Spaces Between Okazaki Fragments! There are many ‘nicks’ in the DNA between the Okazaki fragments Luckily, another enzyme, LIGASE, will come along and fill in this missing information DNA replication video DNA replication video2

Function in DNA replication Enzyme Function in DNA replication DNA Helicase Also known as helix destabilizing enzyme. Unwinds the DNA double helix at the Replication Fork. DNA Polymerase Builds a new duplex DNA strand by adding nucleotides in the 5' to 3' direction. Also performs proof-reading and error correction. DNA clamp A protein which prevents DNA polymerase III from dissociating from the DNA parent strand. Single-Strand Binding (SSB) Proteins Bind to ssDNA and prevent the DNA double helix from re-annealing after DNA helicase unwinds it thus maintaining the strand separation. Topoisomerase Relaxes the DNA from its super-coiled nature. DNA Gyrase Relieves strain of unwinding by DNA helicase. DNA Ligase Re-anneals the semi-conservative strands and joins Okazaki Fragments of the lagging strand. Primase Provides a starting point of RNA (or DNA) for DNA polymerase to begin synthesis of the new DNA strand. Telomerase Lengthens telomeric DNA by adding repetitive nucleotide sequences to the ends of eukaryotic chromosomes.