GENETICS

UNIT FIVE

DAY 1

OPENER

• If you did your Spring Break Genetics Review HW, take it out and raise your hand in the NEXT 30 SECONDS.

AGENDA

• Three Questions—Genetics Review

• Topics for this Unit

• First Learning Target

• Notes/Modeling/Summary:

• The Operon Model of Prokaryotic Regulation of Gene Expression

THREE QUESTIONS

1. What is the function of DNA? How does the structure of the DNA molecule allow DNA to do its job?

2. How is the information stored in DNA accessed and used?

3. How is the structure of the DNA molecule related to the structure of protein molecules? Why do we care about proteins?

• Tables 1-2: Question 1

• Tables 3-5: Question 2

• Tables 7-8: Question 3

ANSWERS1. DNA stores the information cells need to make the

proteins. This information is stored in the order in which the smaller parts of the DNA molecule (the nucleotides) are arranged (like the order of letters in a word give a word meaning).

2. The information in DNA is copied into RNA, in a process called transcription. This information is used by ribosomes to make proteins, in a process called translation.

3. The ‘genetic code’ contained in DNA and RNA is based on groups of three nucleotides, called codons. Each codon “codes” for a different amino acid in a protein.

CENTRAL FRAMEWORK OF MOLECULAR BIOLOGY

DNA RNA Protein Trait

TranscriptionTranslation The

“expression” of genes

REGULATION OF GENE EXPRESSION

CANCER AND THE CELL CYCLE

TWO TOPICS

LEARNING TARGET(S)

LEVEL 3:

I CAN EXPLAIN HOW GENE EXPRESSION IS REGULATED IN PROKARYOTIC CELLS

LEVEL 4:

I CAN COMPARE AND CONTRAST THE REGULATION OF PROKARYOTIC AND EUKARYOTIC GENE EXPRESSION

BUT FIRST. . .

Insulin Human Growth Hormone

Interferon Biofuel?

WHY REGULATE?WHY DO CELLS NEED TO CONTROL WHAT GENES ARE TURNED ON?

DNA

OPERON• Simplest way to control gene expression?

• Stop mRNA transcription• Prokaryotes use operons to control transcription

• An operon is a piece of a DNA molecule that includes:

• Genes• DNA sequences involved in controlling gene expression: on/off

switches

• On/off switch

• Promoter• Operator

• Proteins also part of switch:

• Repressors• Co-repressors (activators OR inhibitors)

TWO BASIC TYPES The INDUCIBLE OPERON

• Normal state: switched OFF• Transcription STARTS when co-repressor binds to repressor

(inactivating it)• Lac operon: regulates production of proteins needed for digesting

lactose

The REPRESSIBLE OPERON

• Normal stated: switched ON• Transcription STOPS when co-repressor binds to repressor

(activating it)• Trp operon: regulates production of proteins needed to make

tryptophan (an amino acid)

INDUCIBLEHOW IT WORKS. . .

GenePromoter Operator

RNA Polymerase

Gene OFF!Gene ON!

Pac Man=RepressorOrange Square=Co-Repressor

mRNA

BINDING BLOCKED!!

REPRESSIBLEHOW IT WORKS. . .

GenePromoter Operator

RNA Polymerase

Gene On!

Gene OFF!

Pac Man=RepressorOrange Square=Co-Repressor

mRNA

BINDING BLOCKED!!

THE LAC OPERONANIMATION STYLE

POWER!

TWO TOOLS:1) ON/OFF SWITCH2) GENE SPLICING

PRACTICE

• Use your models to practice explaining to a partner how BOTH inducible and repressible operons work

• Take turns

• As you explain how operons work, use the: operator, promoter, repressor, co-repressor, RNA polymerase, transcription and gene.

REPETITIONS

• Step One: Go through your notes and highlight each WORD you need to know to describe how operons function

• Step Two: Summarize your notes. Use all the words we have identified.

• This summary is a first draft of the introduction to your lab report.

READ THE LAB

HANDOUT!!

HOMEWORK