DNA Deoxyribonucleic Acid

DNA: True or False DNA is found in all living things. True

DNA: True or False DNA condenses to form chromosomes. True

DNA: True or False DNA replicates during mitosis. False…DNA replicates during INTERPHASE!

DNA: True or False The human DNA sequence would ONLY fill one 1,000 page phone book. False…the human DNA sequence would fill 200 phonebooks!!!

DNA: True or False Your DNA sequence is 99.9% the same as the person sitting next to you. True

DNA: True or False If you stretched the DNA in ONE cell it would reach 6 feet tall. True

DNA: True or False If you stretched the DNA in ALL of your cells it would reach the moon ONE time. False…because it would stretch to the moon 6,000 TIMES!!!!

DNA: True or False Parents and children share 50% of their DNA. True

DNA: True or False Humans and chimpanzees share around 75% of their DNA. False…Humans and chimpanzees share 94-99% of their DNA.

DNA: True or False It would take a person typing 60 words a minute, 8 hours a day, around 50 years to type the human genome. True!

DNA Structure

What is DNA? The information that determines an organism’s traits. DNA contains a code that produces proteins Many things contain and are made of proteins. Skin, hair, bones, etc are made of proteins.

What is DNA? Cont’d Enzymes are special proteins. Enzymes control chemical reactions needed for life. DNA contains all the information for making all proteins for human life.

DNA Structure: DNA is made of repeating subunits called nucleotides. Nucleotides have three parts: Simple sugar Phosphate group Nitrogen base

One Nucleotide Phosphate Group Nitrogen Base Sugar (Deoxyribose)

DNA Structure The simple sugar is called deoxyribose. The phosphate group is made of phosphorus and oxygen.

DNA Structure Four possible Nitrogen Bases: Thymine (T) Adenine (A) Cytosine (C) Guanine (G)

DNA Nucleotides join together to form long chains. “Backbone” Nucleotides join together to form long chains. The phosphate group of one nucleotide joins together with the deoxyribose sugar of an adjacent nucleotide. “Steps”

Adenine & Thymine (A-T) DNA Nitrogen bases pair up Adenine & Thymine (A-T) Cytosine & Guanine (C-G) Complementary bases

Watson & Crick, 1953 Proposed DNA is put together like a “twisted zipper” DNA = 2 chains of nucleotides joined by nitrogen bases

Watson & Crick, 1953 Double Helix Double = DNA has two strands Helix = twisted like a spring, “spiral”

Importance of Sequencing The sequence of the four different nucleotides determines what organism is created. For instance: T-A-A-G-C-A is different than A-G-C-A-A-G Another example: E-A-R-T-H is different than H-E-A-R-T vs.

Importance of Sequencing The more similar the order of nucleotides are, the closer the relationship between 2 organisms

DNA Replication

DNA Replication Replication = to copy Process of copying DNA in the chromosomes Without DNA replication, a new cell would only have half of its information.

DNA Replication T-A-G-C-C-G-T A-T-C-G-G-C-A Because of the pairing- if you have one strand, it is easy to predict the replicated strand. T-A-G-C-C-G-T Remember: A goes with T, C goes with G A-T-C-G-G-C-A

DNA Replication Remember: The nitrogen bases are held together by hydrogen bonds An enzyme (Helicase) goes to those hydrogen bonds and breaks them = Double Helix Unzips

DNA Replication Step 1: Separate the two DNA strands Helicase (enzyme) does this

DNA Replication Step 2: Original DNA strand acts as a template & complementary nucleotides fill in. Primase(enzyme) finds a starting point to connect DNA Polymerase(enzyme) does the connecting

DNA Replication Step 3: Nucleotides connect and a new sugar-phosphate “backbone” is formed.

DNA Replication Each new DNA molecule consists of one original strand and one new strand

So now what??

What’s So Special About Proteins? DNA encodes the instructions for making proteins. Remember proteins make up your bones, skin, etc. Enzymes are special proteins Enzymes control all chemical reactions in an organism

DNA Codes For Proteins Proteins are made up of many amino acids The order of nucleotides in each gene has information on how to make the string of amino acids which is a protein. ESTIMATE: Each cell contains about 19,000-22,000 genes

We need to figure out how to get from DNA to Proteins! DNA makes RNA-That's Transcription RNA makes Protein-That's Translation RNA makes Protein-That's Translation

What is it? What does it do? RNA What is it? What does it do?

RNA vs. DNA RNA Single Stranded- only half of a zipper Contains the sugar Ribose Contains the nitrogen bases: Adenine Uracil Guanine Cytosine DNA Double Stranded- double helix Contains the sugar Deoxyribose Contains the nitrogen bases: Adenine Thymine Guanine Cytosine

RNA It’s job: Copying DNA It’s goal: To create proteins There are 3 types, each with a different job: mRNA= Messenger RNA: copies DNA to take it out in the cytoplasm rRNA= Ribosomal RNA: works on matching mRNA - to create the amino acids in the correct order tRNA= Transfer RNA: gives amino acids to rRNA to produce the protein.

mRNA Brings information (in the form of an RNA strand) from the DNA in the nucleus to the cytoplasm

Ribosomes Where are ribosomes found? In the Cytoplasm A ribosome attaches to the mRNA and reads its information to build a chain of amino acids - That creates a PROTEIN Ribosome mRNA

tRNA Amino Acid The supplier Brings amino acids to the ribosome so that it can assemble the protein

Review Questions How is DNA replicated? What are the steps? What molecule carries information from the nucleus to the cytoplasm? What organelle reads the information and builds protein?

Transcription

Transcription Transcription’s purpose is to create a single stranded RNA molecule rather than a double stranded DNA molecule. This is needed to allow the single stranded RNA to be taken out of the nucleus by the mRNA to the cytoplasm.

Genetic Code with mRNA In order to take the DNA and create a mRNA, there are special codes used. In mRNA, three nitrogen bases together form a code – this is called a codon. Looking ahead: this code is matched with an amino acid. A string of amino acids forms a protein.

Genetic Code with mRNA Most codons code for amino acids. Amino acids link together to form a protein. There are 64 codons – many code for the same amino acid. All are very specific. AUG is the start codon. UAG is one of three stop codons.

Transcription DNA Unzips at a gene RNA nucleotides base pair to the DNA template Finished mRNA detaches and moves to the cytoplasm Remember: Never T’s your RNA

Messenger RNA builds on a DNA template

Translation

Translation: From mRNA to Protein The process of changing the information from an order of nitrogen bases in mRNA into the order of amino acids of a protein Occurs at the ribosome, in the cytoplasm

Translation Steps When mRNA enters the cytoplasm, ribosomes attach to it 20 different amino acids must be brought to the ribosomes for proteins to be made Transfer RNA’s (tRNA) bring the amino acids to the mRNA strand The amino acids are joined to make a specific protein

Transfer RNA’s (tRNA) Transfer RNA’s (tRNA) carry specific amino acids Each tRNA has an anticodon of 3 bases Anticodons and codons are opposites (Complementary)

Translation 1 When a match is made between codons and anticodons- a temporary bond is formed. This places the amino acid in the correct position to enable it to bond with the next amino acid

Translation 2 The next tRNA bonds to it’s codon and then the two amino acid’s bond together. The first amino acid then releases itself from the mRNA

Translation This continues until a stop codon is reached. Amino acid chains then become proteins when they are freed from the ribosome and twist and curl into complex three-dimensional shapes.

Translation