Transcript Document

Lesson 15: Protein Synthesis
and Gene Regulation
Central Dogma
From Gene to Protein
Bodies  Cells  DNA
 Bodies are made up of cells
 All cells run on a set of instructions
spelled out in DNA
Remember…
 Bases match together
A pairs with T
A : T
 C pairs with G
C : G
 weak bonds
between bases
join 2 strands

 can separate easily
What do we know?
 DNA

DNA is the genetic information
 Proteins
proteins run living organisms
 enzymes

 all chemical reactions in living organisms are
controlled by enzymes (proteins)

structure
 all living organisms are built out of proteins
 DNA is the instructions for making proteins
What else do we know?
 DNA


DNA is in the nucleus
want to keep it there = protected
 “locked in the vault”
 Proteins


made by a “protein factory” in cytoplasm
ribosomes
 Need to get gene (DNA) information
from nucleus to cytoplasm



need a messenger!
need a copy of DNA
mRNA
nucleus
DNA
• deoxyribose sugar
• nitrogen bases
– G, C, A, T
• T = thymine
–T:A
–C:G
• double stranded
RNA
• ribose sugar
• nitrogen bases
– G, C, A, U
• U = uracil
–U:A
–C:G
• single stranded
From nucleus to cytoplasm
transcription
DNA
mRNA
protein
translation
trait
nucleus
cytoplasm
The problem with DNA…
DNA (double helix) is too big
to go through the pores in
the nuclear envelope.
RNA (single helix) is small.
DNA gives its information to
mRNA (messenger RNA) to
carry out of the nucleus.
TOO BIG!
Just right.
TRANSCRIPTION
• Making mRNA from DNA
• DNA strand is the
template (pattern)
– match bases
• U:A
• G:C
• Enzyme
– RNA polymerase
mRNA
TRANSCRIPTION
Making mRNA from DNA
T G G T A C A G C T A G T C A T CG T A C CG T
U
U
U
U
U
T G G T A C A G C T A G T C A T CG T A C CG T
TRANSCRIPTION
• Double stranded DNA unzips
T G G T A C A G C T A G T C A T CG T A C CG T
TRANSCRIPTION
• Use RNA polymerase
• Match free floating RNA
bases to DNA bases on one of
the DNA strands
AG
A
G
C
U
A
G
G
U
U
C
A
C
G
A
U
A
C
RNA
A C C polymerase G
A
U
T G G T A C A G C T A G T C A T CG T A C CG T
U
C
TRANSCRIPTION
U instead of T is matched to A
DNA T A C G C A T T T A C G T A G C G G
l I I I I I I I I I I I I I I I I I
mRNA A U G C G U A A A U G C A U C G C C
What do we know NOW?
 DNA

instructions remain in nucleus
 mRNA

A C C A U G U C G A U C A GU A GC A U G GC A
has the instructions for building
proteins from DNA
 Proteins

built as chains of amino acids
 What reads RNA?
need a mRNA reader!
 ribosome

Flash: Central Dogma Transcription
From gene to protein
cytoplasm
Transcription
CELL
Protein
Trait
aa
aa
DNA
Translation
aa
aa
aa
mRNA
aa
aa
nucleus
ribosome
A C C A U G U C G A U C A GU A GC A U GGC A
mRNA leaves
nucleus through
nuclear pores
Ribosomes synthesize amino
acids to make a protein using
instructions on mRNA
What do we ALSO know now?
 mRNA
ribosome
A C C A U G U C G A U C A G U A G C A U GaG C A

has the instructions for building proteins
from DNA
a
a
 Proteins

built as chains of amino acids
 What reads mRNA?

ribosome
a
a
a
a
 What brings the right amino acid to
attach to the protein chain?

need an amino acid transporter!
a
a
a
a
a
a
a
From gene to protein
cytoplasm
Transcription
CELL
Protein
Trait
aa
aa
DNA
Translation
mRNA
nucleus
aa
aa
aa
aa
ribosome
A C C A U G U C G A U C A GU A GC A U GGC A
tRNA
aa
tRNA carries the correct
amino acid (based on the
mRNAcode) to the ribosome.
How does tRNA know which
amino acid to bring?
• When mRNA leaves nucleus it has a blueprint
of DNA’s instructions.
• mRNA goes to ribosomes in cytoplasm
• Ribosomes read the blueprint on mRNA.
mRNA
ribosome
A C C A U G U C G A U C A GU A GC A U G GC A
aa
aa
aa
aa
aa
aa
aa
aa
Using the blueprints…
DNA
TACGCACATTTACGTACGCGG
mRNA
AUGCGUGUAAAUGCAUGCGCC
?
protein
Met Arg Val Asn Ala Cys Ala
How can you code for 20 amino acids with only
4 nucleotide bases (A,U,G,C)?
mRNA codes for proteins in triplets
DNA
TACGCACATTTACGTACGCGG
Codon = set of 3 bases
mRNA
ribosome
AUGCGUGUAAAUGCAUGCGCC
AUGCGUGUAAAUGCAUGCGCC
UAC
Amino
acid
?
Anticodon = set of 3 bases
Met Arg Val Asn
Cys Ala
Ala
AUGcode is UNIVERSAL!
The
• Since all living
organisms…
– use the same DNA
– use the same code
book
– read their genes the
same way
The mRNA code
• For ALL life!
– Uses only 4 bases for
ALL life. (strongest
support for a common
origin for all life)
• Code is redundant
– several codons for each
amino acid
– mutation insurance!
 Start codon


AUG
methionine
 Stop codons

UGA, UAA, UAG
TACGCACATTTACGTACGCGG
AUGCGUGUAAAUGCAUGCGCC
mRNA
DNA
tRNA
Ser
Pro
Met
Ala
Leu
tRNA
Val
A different view of PROTEIN SYNTHESIS
DNA
transcription
amino
acids
mRNA
Can you tell
the story?
ribosome
protein
tRNA
translation
Gene Regulation…Keeping Control!
Every species has
its own number of
chromosomes in
each cell.
Notice:
More is not always
better... Sometimes
it’s just more.
Organism
Number of
Chromosomes
Cat
32
Chimpanzee
48
Dog
78
Cow
60
Human
46
Horse
64
Pea plant
14
Corn plant
20
Mosquito
6
Honeybee
32
Sugarcane
80
Sand dollar
62
Remember…a section on a
chromosome that codes for a
specific trait is called a GENE.
And…
There are lots and lots of
genes on each chromosome!
The job of a gene is to control
the production of proteins.
Not every gene is expressed at the same time.
Gene Regulation = what controls when a gene
is turned on or turned off (expressed).
In bacteria, genes are in groups called
Operons.
Example: E. coli that’s in our digestive system
helps us break down milk.
Each Operon codes for a specific protein.
Has to have a CAP to start.
Are You Lactose
Intolerant?
Here’s how we
metabolize
milk…
Lac operon
Can NOT have a Repressor.
Some questions ask you to
INFER the meaning of a term. If
you cannot recall its meaning
try to figure out how the word
is used outside of science.
Example:
Regulation