The DNA Connection Pages 107-112 Key Concepts: What forms the genetic code? How does a cell produce proteins? How can mutations effect an organism?

The young, white, ring-tailed lemur was born in a forest in Madagascar. White lemurs are extremely rare. Why was this lemur born with such an uncommon phenotype? To answer this question, you need to know how the genes on the chromosome control an organism’s traits. Introduction

The Genetic Code A review: Chromosomes are made up of DNA A DNA molecule is made up of four nitrogen bases: A, T, C and G A gene is a specific section on the DNA molecule that codes for a protein A single gene could contain several hundred to a million or more bases.

The Order of the Bases are Important The order of the bases determines exactly what protein will be made. Every 3 letters (codon) codes for an amino acid. Chains of amino acids build a protein. Amino acids are like pearls on a necklace. Pearls are stranded together to form a necklace. Amino acids are stranded together to form a whole protein.

So, how does the cell make proteins? The process is called PROTEIN SYNTHESIS. The cell uses the information from a gene on a chromosome to make a protein. Happens on a ribosome in the cytoplasm Remember – the ribosome is known as the “Protein Factory.” This is why. Ribosomes

Protein Synthesis requires DNA and RNA to work together. What is RNA? The “messenger” that carries the code from DNA out to the cytoplasm. DNA RNA

How Are DNA and RNA Different? Number of strands DNA is double-stranded (known as the “Double Helix”), while RNA is made up of only one strand Type of sugar - The sugar in DNA is called deoxyribose, while the sugar is RNA is called ribose Nitrogen Bases - DNA is made up of A, T, C, and G, while RNA is made up of A, U, C, and G. Thymine is replaced with URACIL.

Types of RNA Messenger RNA (mRNA) Transfer RNA (tRNA) A waitress copies down the order from the customer. Just like mRNA copies down the code from DNA. Messenger RNA (mRNA) Job: copies the code from DNA in the nucleus and carries it out to the cytoplasm Transfer RNA (tRNA) Job: carries the amino acids to a ribosome to form a growing protein. The chef puts together all the ingredients to build a meal. Just like tRNA puts all the amino acids together to build a protein.

How it all Works. STEP 1 – Messenger RNA is Made STEP 2 – Messenger RNA Attaches to a Ribosome STEP 3 – Transfer RNA Attaches to messenger RNA STEP 4 – The Protein is Complete

STEP 1 mRNA is made DNA unzips mRNA is made when bases match up to the DNA strand. (U matches up with A)

Step 2 mRNA attaches to a ribosome mRNA exits nucleus and enters the cytoplasm The mRNA moves along the ribosome and every 3-letter code is read. (called a CODON)

Step 3 tRNA attaches to mRNA tRNA carries over an amino acid. It matches up to the codon with an anti-codon. The protein chain grows with each amino acid.

Step 4 The protein is done. The ribosome reaches a STOP codon. The protein is released out to the cell to do its job. Proteins can be short or very long (100’s or 1000’s of amino acids).

Here’s how the whole process works http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html

What happens if the wrong protein is made? Mutations occur Any change that occurs in a gene or a chromosome. Can occur randomly (naturally) Can be deliberately caused in the laboratory by scientists Can be inherited Are not always harmful

Types of Mutations Inherited From mutations found in parent’s sex cells Acquired Changes in body cells during the lifetime of a person

ALBINOS Little or no pigmentation in the eyes, skin, and hair. Inherited an altered copy of a gene that does not work correctly. The altered gene does not allow the body to make the usual amounts of a pigment called "melanin". True albinos have pink eyes and skin.

Mutations can be helpful Mutations in potatoes causes a new variety to form. These Katahdin potatoes are resistant to some diseases that attack other varieties of potatoes. They also look and taste better than other potatoes.