DNA – Life’s Code Biology 2

The DNA Molecule When we discussed mitosis and meiosis we talked about “genes” – DNA is what makes genes DNA stands for deoxyribonucleic acid It is a molecule that makes up genes and determines the traits of all living things All living things contain DNA in their cells The structure is similar to that of a ladder

The DNA Molecule Ladder Upright Ladder Rung

The DNA Molecule Six features of the DNA model Two main sides (similar to the ladder) Sides are made of alternating sugar and acid molecules Parts connect the sides together (similar to the rungs of a ladder) called nitrogen bases There are 4 types of nitrogen bases: adenine (A), cytosine (C), thymine (T), guanine (G) The four bases join together in certain ways The “ladder” is twisted in a spiral

The DNA Molecule Nitrogen bases: Adenine always pairs with thymine Guanine always pairs with cytosine They fit together similar to that of a puzzle All your DNA comes together to form chromosomes Remember: chromosomes are found in the nucleus of cells and your body is made entirely of cells

Hoe DNA Works DNA is a code for life So, the code determines if the organism is a plant or animal, is tall or short, have dark or light hair and every other unique thing we see in life Example: GAGTGAGGCTTC CTCACTCCGAAG This code is a code

How DNA Works The code is read similar to how you read a sentence The code starts on the right and continues reading until a stop code is reached For example: you read and understand each word and when you reach a period (.) you know the sentence is complete. The code gives the cell information it needs to function

How DNA Copies Itself to RNA Think about the ladder model of DNA again The ladder breaks apart into 2 sides A strand of RNA attaches itself to the DNA and makes a copy of the code – the only difference is RNA does not have the nitrogen base thymine (T), but has uracil (U) which pairs with adenine (A) Example: AACGTTT DNA UUGCAAA RNA

How DNA Copies Itself to RNA The copied mRNA detaches from the DNA The DNA closes back up The mRNA moves out of the nucleus into the cytoplasm The mRNA attaches to the ribosome and gives the information tRNA to make the proteins

Making Proteins Remember: your cells have ribosomes, which make proteins & ribosomes are located in the cytoplasm (not the nucleus where the DNA is found) DNA codes for the proteins that the ribosomes make There has to be a messenger to relay information from the DNA (in the nucleus) to the ribosomes (in the cytoplasm)

Making Proteins The messenger is called ribonucleic acid or RNA Types of RNA Messenger RNA (mRNA) Transfer RNA (tRNA) The DNA copies it’s information onto the mRNA and the mRNA travels out of the nucleus into the cytoplasm where the ribosome is and give the information to the tRNA