Something to Think about …… Did you know that some of your cells are dying right now? You may live to the ripe old age of 100, but most of your cells will have been replaced thousands of times before you blow out the candles on that birthday cake. Every time cells divide to produce new cells, DNA must first be copied. Before we replicate some DNA, let’s recap …………………………….

Chromosomes, Genes, and DNA Chromosomes and genes are made of DNA. Genes are stretches of DNA that code for a trait such as hair color or eye color. Chromosomes are threadlike structures found in the nucleus that contain genetic information (genes). Hair Color Eye Color

Chromosomes, Genes, and DNA cell genes nucleus base pairs DNA (double helix)

DNA Replication Why does DNA need to replicate? DNA is located inside the nucleus and NEVER leaves the nucleus. However, ALL cells need the genetic code (DNA) to function. DNA will make a copy of itself and that copy “leaves” the nucleus. Do you remember “who/what” goes in the nucleus to copy the DNA? RNA When in the cell cycle does the DNA get replicated? The S-Phase of Interphase

How does DNA replicate? The process by which DNA is copied during the cell cycle is called replication. When DNA is copied, every cell has a complete set of DNA. DNA simply stores the genetic information. Enzymes and other proteins do the actual work of replication. DNA Polymerase: enzymes that form bonds between nucleotides (phosphate, deoxyribose, nitrogen base) during replication.

Before DNA replicates, do you remember: What are the 4 nitrogen bases of DNA? How do these nitrogen bases pair up? Adenine, Guanine, Thymine, Cytosine AT GC

DNA Replication The original strand of DNA “unzips” and nucleotides base pairs separate. The enzyme Helicase is responsible for the “unzipping.” New DNA strands forms. Original DNA Strand Quick Illustration New DNA Strand

DNA Replication Video & Quick Question During DNA replication, what is the complementary strand of the original DNA strand below? A T G G C T A DNA Replication YouTube Video

After Replication……Transcription Begins…. Remember, DNA never leaves the nucleus so RNA makes a copy of the DNA. The process of RNA making a copy of DNA inside the nucleus is called transcription. mRNA (messenger RNA) sends the message/copy of DNA to the cytoplasm of the cell. RNA gets the message out  How does mRNA tell the cell what to do? mRNA codes for a protein and proteins keep a cell alive What are the nitrogen bases for RNA? Adenine, Guanine, Uracil, Cytosine How do RNA nitrogen bases pair up? AU GC

RNA Transcription DNA unzips again (seperates) The enzyme RNA polymerase bonds nucleotides together in a chain to make a new RNA molecule When complete, RNA detaches and DNA zips back together Transcription produces mRNA, rRNA, and tRNA Once in the cytoplasm, mRNA attaches to a ribosme to make a protein Remember ….. Protein synthesis takes place in ribosomes

Transcription Questions Complete the following base pairing. Pay attention to which process you are pairing up with. Original DNA: A A T G C T DNA Replication: ____________ Transcription: ____________

Translation Translation is the process that translates a mRNA message into a polypeptide. The carrier is tRNA. Polypeptide??????? Polypeptides make up proteins. The building blocks of proteins are amino acids. During the process of translation, 3 nitrogen bases sequenced together are referred to as a codon. Codons will code for an amino acid. In addition to coding for amino acids, there are stop codons and a start codon. Start and Stop codons begin and end the translation process.

Brain Teaser Can you handle it? Suppose an mRNA molecule in the cytoplasm had 300 nucleotides. How many amino acids would be in the resulting protein?

Translation How does a cell translate a codon into an amino acid? Set of 3 mRNA’s is a codon. tRNA forms an anticodon which then carries the amino acid.

Coding for Amino Acids Let’s try it  AUA: ______________ GAG: UUA AAC: UGA:

Another Brain Teaser  Think about this Base Pairing…… Original DNA: T G A C C T DNA Replication: ______________ Transcription mRNA: ______________ ( set of 3 = codon ) Translation tRNA: ______________ ( anticodon ) Amino acids: ____________________

Transcription and Translation Quick Video http://www.youtube.com/watch?v=983lhh20rGY

Why all this just for amino acids? Amino acids are used in every cell of your body to build the proteins you need to survive. Amino acids repair tissues, build cells, form antibodies, carry oxygen …. Just to name a few! There are 20 amino acids used to make proteins in your body. Amino acids form long chains which are called proteins.

This was just way toooooo much information !!!!! To put it simply  DNA replicates inside the nucleus ( AT GC ) 2. RNA goes in to make a copy ….. mRNA ( AU GC ) RNA goes back into the cytoplasm and attaches to a ribosome mRNA forms codons that code for amino acids ( AU GC ) Replication Transcription Thank goodness!!! This was just way toooooo much information !!!!! Translation