The Wonderful World of DNA (Deoxyribonucleic Acid)
Review • Everything is made of matter • Matter is made of molecules • Molecules are made from elements • DNA is a molecule that is made from other molecules
DNA Fun Facts • DNA was first isolated in 1869 by Friedrich Miescher. • James Watson and Francis Crick figured out the structure of DNA in 1953. Although they did “borrow” much of the research to figure it out. • DNA is a double helix. • One chromosome can have as little as 50 million base pairs or as much as 250 million base pairs. • If unwound and tied together, the strands of DNA in one cell would stretch almost six feet but would be only 50 trillionths of an inch wide. • Over 99% of our DNA sequence is the same as other humans’
DNA is important because • It has a really long, scientific name • It is the instructions that code for the creation and maintenance of living things • It is what mitosis uses for its phases • All of the above makes DNA important
A double helix is like a • Spiral Staircase • A twisted ladder • A piece of licorice • More than one of the above are correct
The DNA model • It all starts with the “backbone” • A Phosphate is connected to the deoxyribose sugar • The bonds holding them together are STRONG. • We don’t want the DNA to separate along backbone
The DNA model • The building block is a nucleotide • DNA is built from small similar parts called nucleotides • It consists of three parts: • A phosphate • Connected to the Sugar • A nitrogen base connected to the sugar • There are 4 nitrogen bases: Adenine, Thymine, Guanine and Cytosine • They pair up on opposite sides of the DNA • Adenine with Thymine & Cytosine with Guanine
DNA has two backbones. • True • False
Nitrogen bases in DNA pair up like this: • A – C, G - T • G – A, T - G • A – T, G - C • They don’t pair up at all
A nucleotide is like • A lego • A brick • A puzzle piece • All of the above
The Code • The A, T, G & C’s are set in an order for a specific trait • The code can only be read when the DNA is open • It is coded in 3 letter sequences. • Each 3 letter sequence is called a CODON.
Which would be an example of a codon? • CBA • GATTACA • KFAN • None of the above
Reading the Code • When DNA is read, it is read one gene at a time • Each gene codes for a specific trait • When a gene is ready to be read, DNA unzips • A molecule called mRNA is formed as a copy of the code
mRNA • mRNA (messenger RNA) • Made with Ribose sugar instead of Deoxyribose • Only a single strand, but still twisted • Uses Uracil as a nitrogen base instead of Thymine • Built as a match to DNA
Reading the code • Each codon is represented by one AMINO ACID. • Amino Acids are assembled in the order of the code. • When assembled they are called PROTEINS.
We still haven’t said how the code is read!? • The actual reading is done by the RIBOSOMES outside of the nucleus. • They call for molecules call tRNA that carry specific amino acids • The tRNA’s bring in the aminos and attach them to the ones that are there, creating a long line of amino acids call a PROTEIN.
tRNA • tRNA (transfer RNA) • Is a short strand of RNA • Only 3 nucleotides long (1 codon) • Carry one specific amino acid that is specific to the code that it has
The Process is in Two Stages • Stage 1 (Transcription) • DNA unzips • mRNA is made • mRNA is released into nucleus • DNA zips back up
What is created in the end of transcription? • 2nd half of DNA • tRNA • Unzipped DNA • mRNA • None of the above
Stage 2 (Translation) • mRNA goes out of the nucleus • Attaches to a ribosome at one codon • Ribosomes read the code and call for one of the tRNAs with the opposite code • tRNA matches up with the mRNA at the ribosome, attaches its amino acid to the others that are there (peptide bond between aminos), then leaves • Continues to do this until the mRNA runs out • mRNA returns to the nucleus and breaks up into its nucleotides. • The amino acid chain is the PROTEIN (or a polypeptide) and is released to control the trait
What is created in the end of translation? • Protein • tRNA • Unzipped DNA • mRNA • None of the above