Genes, Proteins,

Transcription & Translation

Ch. 11.4-11.5

Review

• DNA Structure– What does a double helix

consist of?

– What are the base pairing rules?

• What are the steps of Replication

1. DNA strands unzip• Help of replication bubbles

2. New bases attached to old strand

3. New strand formed

Objectives

1. Trace info flow from DNA --> protein

2. Describe DNA transcription

3. Describe how RNA is translated to protein

Protein Synthesis Analogy• The synthesis of proteins

from genes is a two-step process:

1. As in house construction, first the plans must be found in the planning dept. and photocopied. (Transcription)

2. The blueprints are taken to a construction site, read, and “translated” into walls, roof, etc. (Translation)

The DNA Alphabet• Language of genes

– written in sequence of bases on DNA strand

• Each base is a “letter”– How many letters in the “gene” alphabet?

• Each gene is a “sentence”• Human’s have 30,000 to 35,000 genes!

The Human Genome: Our Instruction Book

• 3 billion letters long!• We consist of 100

trillion cells!• Every cell contains

copies of DNA (3 billion letters!)

• DNA in one cell is about 6 feet in length (if unraveled).

How do scientists do it?Sequencing the Genome

Why do we care about proteins?

• Proteins are body’s worker molecules– Involved in structure (hair, muscles, enzymes,

etc)

• Here is one example and a brief summary of how proteins are made . . .

• Online Activity 11.4

The Information FlowProtein Synthesis in a Nutshell

• DNA --> RNA --> Protein

• RNA:– Ribonucleic Acid

• RNA contains the base Uracil (U) INSTEAD of Thymine(T)

• What will A on the DNA pair with on the RNA if there is no T?

• U!

• If you have an A look for the T. If no T, then use U.

Protein Synthesis Transcription & Translation

2 steps 1. Transcription:

• Messenger RNA (mRNA) transcribes message from DNA• Message contains directions on

how to make protein

• Pairs with one strand of DNA bases

• Remember, U pairs with T

• Exits nucleus with directions for making proteins• Same message, different form

Protein Synthesis Transcription & Translation

2. Converting nucleic acid language (mRNA) into amino acid language

• mRNA meets up with Transfer RNA (tRNA)

– tRNA = the interpreter

• Attaches to ribosome

tRNA deciphers language by reading codons on mRNA

• Codon:– a three-base “word”

– Codes for one amino acid

• Translation:• Converts nucleic acid

language into amino acid language

• Russian to English

• How does the translation of codons work?

Understanding Codons on the mRNA

• Each codon stands for a particular amino acid

• How do we read this table?• If mRNA has a codon

AUG, what is the amino acid?– methionine

• What about CAG?– glutamine

• What about CCC?– proline

• What about UGA?• List of the 20 amino acids

Protein Synthesis continued

• tRNA’s match up with appropriate codons on mRNA.

• They bring amino acids with them

• Amino acids connect and form polypeptide (protein)

Proteins and mRNA

Candy Factory Analogy

What it all means• With the help of ribosomes, mRNA is converted into

individual amino acids• These amino acids form a polypeptide• This determines who you are and how your body operates!• Hopefully these short animations will make this process more

clear . . .• Activity 11.5• Narrated short animation• Wisconsin site with animation• Lewport's animation• Protein synthesis activity with overhead projector - building a

chain . . . • Protein synthesis activity –moving around the classroom