honors biology gene expression. construct and revise an explanation based on evidence for how...
TRANSCRIPT
Honors BiologyGENE EXPRESSION
Construct and revise an explanation based on evidence for how carbon, hydrogen, and oxygen from sugar molecules may combine with other elements to form amino acids and/or other large carbon-based molecules.
Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.
OBJECTIVES
What is gene expression?The process of using DNA
code to make protein
GENE EXPRESSION: WHAT
When does gene expression occur?All the time!Example: during development (Hox genes and body
plan)Example: in your cells NOW (such as hormones )
GENE EXPRESSION: WHEN
Who goes through gene expression?
All cellsAble to turn on/turn off
Cell type dependent Muscle cells turn on the genes for
what they need (like making actin), turn off the genes for what they don’t (like making lactase)
Cellular need dependent Turn genes on/off depending on
cell’s needs at the time (such as food molecules present needing digestion)
Environmental conditions Soil pH and hydrangeas (the more
acidic the pH, the bluer the flower)
GENE EXPRESSION: WHO
Human genes cannot all be active at the same time If they were, all the cells in our bodies would look the
same and have the same function(s)For specialization to occur, some genes or gene
products must be active while others are turned off or inactive
GENE ACTIVATION
Where in the cell does gene expression occur?
Cell structures and their function: Nucleus
Store DNA Ribosome
Make protein Rough endoplasmic
reticulum Ribosomes attach
Vesicles Transport proteins around
cell Golgi body
Modify/complete protein Cell membrane
Control entry/exit of materials
Vacuoles Store materials
GENE EXPRESSION: WHERE
Why do organisms express genes?Proteins carry out the essential functions of life
through systems of specialized cells
GENE EXPRESSION: WHY
How are genes expressed?2 steps:1. Transcription
In nucleus mRNA is made from DNA
2. Translation In cytoplasm Protein is made from mRNA
GENE EXPRESSION: HOW
1. DNA section with desired gene is unzipped by RNA polymerase
2. RNA polymerase adds complementary nucleotides, mRNA strand is made
3. When a stop sequence is reached, mRNA separates from DNA and DNA is re-zipped
4. mRNA leaves the nucleus
TRANSCRIPTION
1. mRNA finds a ribosome2. Ribosome scans mRNA
for the start codon (AUG)3. tRNA with the
corresponding anti-codon carries in amino acid
4. Ribosome shifts down, reads the next codon
5. Next tRNA moves into place
6. Amino acids bond together
7. Repeats until a stop codon is reached and protein is released
TRANSLATION
How does the cell determine what amino acid goes with the mRNA’s codon?
CODON = AUG
Start in the center and work your way out
A
U
G
Amino acid is methionine
Try finding the amino acid for the codon ‘CUA’
LEUCINE
Codon Table