 Replace old cells  Growth  Repair cuts/ wounds  Reproduction

 DNA must replicate, or make an exact copy of itself to put into new cells. 1 DNA2 DNA DNA Replication

 1: DNA double helix unwinds.

 2: Hydrogen bonds break and strands begin to unzip.

 3: Free nucleotides pair up with nucleotides on parent strand to form a complementary strand.

 At the end of replication, two IDENTICAL daughter strands of DNA have been formed!

 Each new strand pairs up with an old strand two produce two DNA molecules each containing one parent (old) and one daughter (new) strand.

 After DNA is replicated, a cell splits to form two cells that each get one copy of the DNA!

 Riboonucleic acid  RNA is used to make a temporary copy of the information contained in the DNA of an organism.

 Messenger RNA (mRNA)  Transfer RNA (tRNA)  Ribosomal RNA (rRNA)

 Single helix  Single strand  Backbone of sugar, phosphate  Nucleotides: ◦ Adenine ◦ Guanine ◦ Cytosine ◦ Uracil

 DNA is in the nucleus of the cell BUT  Proteins are made in ribosomes in the cytoplasm

 Instructions from DNA need to be carried to ribosomes so proteins can be made.  Why would it be a bad idea to send the DNA to the ribosomes? DNA Protein Manufacturing

 Each cell only has one copy of DNA, so it has to be protected in the nucleus.  Thousands of mRNAs can be made from a DNA template strand, but DNA is only replicated to make a new cell.

DNA mRNA transcription

 To make a copy of something  Examples: ◦ Rewriting or typing an old documents ◦ Typing the lyrics to a song ◦ Taking notes from a PowerPoint!

 DNA contains all the information for making the proteins that make up our bodies.  DNA never leaves the nucleus of the cell. If this is true, then how does the rest of the cell get information from the DNA?

 1: DNA unwinds  2: DNA unzips

 3: RNA nucleotides are combined by RNA polymerase to form messenger RNA (mRNA) strand

 4: DNA rezips and winds back up

 mRNA leaves the nucleus through a nuclear pore and travels to a ribosome

 Proteins are made from the mRNA!

 DNA contains the instructions for making proteins  The instructions are in code  The code is based on the sequence of amino acids—each protein has a particular sequence  Each amino acid has a 3-nucleotide code (like AGA or GCC)  The code is transferred to mRNA

 3 bases of mRNA= 1codon = 1 amino acid

 There are 20 amino acids.  The hundreds of thousands of proteins are made with different sequences of amino acids—300 long or more

 Each codon is specific to an amino acid.

 One sequence ALWAYS tells a ribosome where to start an amino acid chain.  AUG codes for met (methionine)  Every amino acid chain starts with a methionine in humans. AUGAUG

 Tells a ribosome where to stop reading a strand of mRNA  There are 3 stop codons: UAA, UAG, and UGA.

 What amino acid is coded by: ◦ GCU: ◦ GAA: ◦ CUA: ◦ AUU: ◦ UCG:

 What amino acid is coded by: ◦ UGG: ◦ AUA: ◦ GUC: ◦ GAA: ◦ UUU:

mRNA protein translation

 In a ribosome

 Transfer RNA- bring amino acids to ribosome in order to make a protein made of amino acids

 Each 3 base sequence of mRNA is known as a codon and is specific for a particular amino acid.

 1. tRNA molecule finds and attaches to the specific amino acid it is designed to recognize Steps to Translation – tRNA attaches to specific amino acid

 2: tRNA molecule (with its amino acid) attaches to mRNA codon

 2: A peptide bond is formed between amino acids.

 3: tRNA molecule exits the ribosome. The ribosome shifts down the mRNA.

 T: tRNA and amino acid  A: Attachment  P: Peptide Bond  E: Exit

 A chain of amino acids= protein!

 Protein gets shipped to a part of the cell to do a specific job.  mRNA is broken down into bases that can be used to make new mRNA or translated again to make another protein