DNA Structure and Function

Review! Nucleus : “brain” of the cell. Chromosomes: found in the nucleus.

DNA BIG Picture Chromosomes are made of DNA. DNA has your genes on it. DNA has the instructions for making all proteins for the organism. DNA is unique to each individual. DNA determines how an organism looks and functions (traits). Each human has about 30,000 genes on the DNA.

DNA Deoxyribonucleic acid Located in the nucleus of a cell. Is a type of nucleic acid. Made up of repeating nucleotide subunits.

DNA Codes for Proteins All living things contain proteins. Proteins are essential to all of life. ENZYMES ARE PROTEINS!! Enzymes control all the chemical reactions in an organism and are extremely important molecules in biology. DNA contains all of the information needed to build all of the proteins for our bodies.

1 nucleotide looks like: Phosphate Group Deoxyribose Sugar Nitrogenous Base 4 types:Adenine (A) Guanine (G) Cytosine (C) Thymine(T)

2 strands so bases can pair up A binds T only C binds G only P S P S A C Strand 1 P S P S T G Strand 2 Phosphates + sugars on the outside Bases on the inside (Bases fit like puzzle pieces) Remember DNA is like an Oreo Phosphates + sugars = cookies Bases = cream filling BASE PAIRING RULES

What holds DNA together? A T have two hydrogen bonds P S P S A C Strand 1 P S P S T G Strand 2 G C have three hydrogen bonds

Two strands of nucleotides twist together  double helix James Watson and Francis Crick discovered the double helix structure (They won the Nobel Prize)

How does DNA carry information? DNA carries information in the form of nucleotide sequences. For example: –The sequence ATATGCTCTA carries different information from the sequence CGGTATTAAC. Different combinations of the same 4 nucleotides creates a near infinite number of unique genes.

DNA is complementary Bases on one strand match up with the bases on the other strand (A-T and G-C) Example: Strand 1- ATG GGC CTA Strand 2- TAC CCG GAT

DNA Replication  During cell division (interphase), chromosomes replicate to form exact copies to pass along to daughter cells.  That means the DNA replicates!  The DNA unzips and 2 new strands form.  A complete, exact copy of DNA is created.  Each side serve as a template for the other side (called semi- conservative replication).

DNA never ever leaves the nucleus DNA is the master copy of the directions a cell needs to live so it needs to be protected DNA in the nucleus is safe But DNA in the cytoplasm can be destroyed

RNA Ribonucleic Acid Building Blocks:nucleotides A nucleotide is: –A sugar (ribose)* –A phosphate –A nitrogen base RNA has 4 nitrogen Bases (just like DNA) –Adenine –Guanine –Cytocine –Uracil ** RNA is only a single strand***

Three types of RNA**** Messenger RNA (mRNA)- copies info from DNA and takes the message to the cytoplasm. Ribosomal RNA (rRNA)- makes up ribosomes, assembles proteins. Transfer RNA (tRNA)- transfers amino acids to the ribosomes to become proteins.

Protein Synthesis Overview Protein synthesis occurs in two steps: 1.Transcription 2.Translation

Scribes Scripts Copy script for actors

Transcription Definition: RNA is made from 1 gene in DNA The type of RNA made is called mRNA (messenger RNA) because it sends a message from DNA to the cytoplasm DNA safe in the nucleus Uses mRNA To send a message to the cytoplasm

Transcription  Enzymes unzip one gene in DNA  Match up bases to one side of a gene in DNA  mRNA detaches from the DNA, DNA joins back together  mRNA moves out of the nucleus and into the cytoplasm DNA: GAG AAC TAG TAC RNA: CUC UUG AUC AUG For figuring out RNA: A binds U C binds G

How does mRNA tell the cell what to do? mRNA is a message that codes for a protein Proteins are made in the cytoplasm (at the – ribosomes) Translation (protein synthesis): Process of making a protein Proteins are made up of amino acids (small building blocks) -There are 20 different types of amino acids Amino Acids Protein

Transcription happens in the nucleus. An RNA copy of a gene is made. Then the mRNA that has been made moves out of the nucleus into the cytoplasm Once in the cytoplasm, the mRNA is used to make a protein Cytoplasm of cell Nucleus DNA mRNA

Translation Ribosome reads the mRNA and puts together protein “Translating mRNA into protein”

Cytoplasm Nucleus Ribosome Process of Translation 1. mRNA moves out of nucleus through nuclear pore and into cytoplasm 2. mRNA attaches to a ribosome

Cytoplasm Nucleus Ribosome Process of Translation 3. Transfer RNA (tRNA) decodes the mRNA and brings amino acids to build up the protein tRNA Amino acid Anticodon (3 bases on tRNA): Matches up to codons on mRNA

Cytoplasm Nucleus Ribosome Process of Translation 4. Protein (chain of amino acids) detaches from ribosome and goes off to work in the cell

Ribosome

tRNA Molecule

Polypeptide

¼ hemoglobin protein

Transfer RNA (tRNA) Piece of RNA Transfers 1 amino acid to protein being made at ribosome Translation

Ribosome Helps line up the mRNA and tRNA Part of the ribosome is actually made of RNA. Can you guess what they are going to call this type of RNA? rRNA Translation

Genetic Code Codon: group of 3 mRNA nitrogen bases that code for a specific amino acid DNA:GTT  3 Nucleotides Codon Chart Amino acid: Gln mRNA: CAA  codon tRNA: GUU  anticodon

There are 64 codons that code for 20 amino acids … 4 3 = 64 different possible codons How is this possible? …. More than one codon may code for an amino acid The genetic code is said to be universal because it is the same in almost all organisms Worm – AUG = methionine Human – AUG = methionine Example: CGU, CGC, CGA, CGG, AGA, & AGG all code for arg

Central dogma of molecular biology DNA RNA Protein Directions to make proteins are safely stored in the nucleus Carries the directions to the cytoplasm Work to keep the cell alive Transcription Translation

DNA: The Stuff of Life DNA Structure and Gene Expression

While it might be hard to see, it’s in there, and it is in every single cell of every living organism on our planet.

What is the relationship between, chromosomes, DNA and genes? All of the genetic information is stored in the nucleus of every cell in structures called “Chromosomes” For humans, we have 23 pairs of chromosomes in virtually every cell in our body

Nucleotide Sequencing The genetic code in DNA is based on the sequence of these letters.Each gene will have a specific number of nucleotides/base pairs (length) and sequence of letters. For example:Gene 1204-B5 Person A: ATTGCACGATAACGA Person B: TCGATCAAACGCATA Although they have same number of base pairs in the same gene, the sequence of letters makes them different, thus a different version of that trait will be expressed.

1.Use the ribosome sheet to create your own sentence. It must have at least 5 words and be school appropriate. 2.Write the mRNA sequence for your “protein.” 3.Write the DNA sequence for your “protein.”