genetics unit five day 1. opener if you did your spring break genetics review hw, take it out and...
TRANSCRIPT
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
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
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
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.