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AP Bio notes on From Gene to Protein – Ch. 17
The relationship between genes, proteins and traits:
An example: One of Mendel’s pea plant traits was ______plants, a recessive
trait. Dwarf plants lack ______hormones called ______
because the ______(a protein) they need to make gibberellins is coded for
incorrectly in their ______.
Another example: The different ______color mutations in Drosophila are because of
lack of the particular ______that catalyzes the next step in eye color pigmentation.
Evidence for the “One gene-one enzyme” theory:
George ______and Edward ______worked with a bread mold
called Neurospora. Wild type Neurospora which can survive on ______media
(which is agar, organic salts, glucose and the vitamin biotin). They used ______on
Neurospora to cause mutations, then put the mutants in minimal medium and found they
could ______survive. The mutants were unable to synthesize the necessary amino acid
______. By adding different nutrients to the media, they discovered that the
mutations caused defective ______at different steps of the process of producing arginine.
Medium: Minimal medium Minimal medium Minimal medium Minimal medium
+ ornithine + citruline + arginine
Wild type grows grows grows grows
Mutant A - grows grows grows
Mutant B - - grows grows
Mutant C - - - grows
From this they determined that Neurospora must use this process:
Enzyme A Enzyme B Enzyme C
Precursor à à à Ornithine à à à Citruline à à à Arginine
Mutant A must ______enzyme A, mutant B must lack enzyme ____ and mutant C lacks enzyme C.
A different ______codes for each of the different enzymes in the process.
The irradiation ______a particular gene which would no longer function.
Think of each ______as a bridge to the next step.
If the bridge is ______, you cannot continue along the highway to reach your final
destination. But if you start on the road ______the bridge, you can continue to the end.
Their conclusion is called the “one ______– one enzyme” theory. This is the
concept that each gene must contain the ______for making one
type of ______.
Now their idea has been expanded to include ______and ______, so one gene codes for one protein or one polypeptide.
RNA and why it is needed
Remember that DNA is found in the ______of the cell, but that protein
production occurs in the ______by the ______. So the message from the DNA must be taken from the nucleus to the cytoplasm. For this job,
the cell uses ______. The ______of the ______
of the DNA tells the cell which order to put ______when
building a protein, which determines the ______of protein that is made. A group
of ____ bases on the DNA strand code for one type of amino acid. This is called the
______.
Ex. AAA codes for the amino acid phenylalanine.
RNA – ______acid
Made of ____ strand of ______.
The nucleotides have ______for their sugar.
The bases in RNA are:
Adenine and Guanine (______)
Cytosine and ______(pyrimidines)
(This is different from DNA, which had ______instead of uracil)
3 Kinds of RNA
1. ______RNA (mRNA) – carries ______from the
DNA (in the ______in eukaryotic cells) out to the ribosomes in the cytoplasm.
2. ______RNA (tRNA) – carries ______to the ribosome to be joined together in proper order to make a protein.
3. Ribosomal RNA – part of the structure of a ______(circular structure in cytoplasm where proteins are made).
Process of protein synthesis
______– the process of making a protein from the DNA code.
Step One: ______– the process of making ______from the
______code to bring the code to a ribosome where the ______is made.
Only ______of the DNA is used for this, it is called the ______.
Remember that a chromosome has a long strand of ______with many ______, but we will make RNA from only part of that strand since we want just 1 gene’s protein.
1st – A ______attaches to the DNA strand at the end of
a series of DNA nucleotides called the ______because it has several TATA nucleotides.
2nd – More transcription factors attach to ______and then an enzyme called ______
______binds to a “start” signal on the DNA which is always ______on the DNA.
The ______box and the ______signal have about 25 nucleotides between
them and the whole series is called the ______.
3rd – RNA polymerase ______down the DNA and ______the two strands of DNA.
4th – As RNA polymerase ______along one strand of the DNA it ______
______RNA nucleotides with the exposed DNA bases. The strand it uses is called the
______strand. It is the side that allows for the
______additions of RNA nucleotides to the free 3’ end of the forming strand.
Base pairing is just like for DNA except ______pairs with adenine.
G - A - T - C -
DNA - RNA DNA – RNA DNA - RNA DNA – RNA
Diagram:
RNA polymerase adds 60 nucleotides per ______.
About ______RNA polymerase molecules act on a gene, one after another, and each makes a strand of mRNA at the same time.
5th – RNA polymerase reaches a “______” signal on the DNA. One of the stop
signals is the codon ______. The RNA polymerase still continues on for
many nucleotides past this signal until it finally stops. ______releases the
RNA molecule that was made, which is called ______.
6th – The DNA “______” back up.
7th – Now the pre-mRNA strand is ______. A ______with 3
phosphates attached is added to the ______end, called the ______. At the 3’
end, a ______made of 50-250 ______nucleotides is added.
So the mRNA molecule now looks like this:
8th – RNA ______occurs. The DNA (and mRNA) contain unnecessary
sequences that do not code for the protein called ______that need to be
______. These are interspersed within the parts that do code for the protein, called
______(because they will be the part that ______the nucleus).
Small particles of RNA and protein called ______
______or ______attach to other proteins to form a larger
complex called a ______. The spliceosome attaches to the mRNA at
an ______and cuts out the intron and splices the ends of the exons together.
Diagram:
______- are RNA molecules that act as ______(such as
snRNA). So not all enzymes are ______.
Because genes are split with introns that are ______, some genes actually
code for ______proteins depending which sections are removed. This is
called ______.
Ex. Sex differences in fruit flies depend on how males and females splice their RNA
Each ______may code for a different functional ______of a particular protein.
Exon shuffling could lead to new ______with new function combinations.
Diagram:
The Genetic Code – what the RNA sequence ______.
______– a series of ______on a messenger RNA molecule that
code for one ______or “start” or “stop”.
Ex. AUG = start
UUU = phenylalanine (an amino acid)
UGA = stop
(See p. 330)
Step Two of Protein Synthesis – ______– process of bringing
______from the cytoplasm and joining them in the proper order
according to the mRNA code. Occurs in the ______of the cell.
Translation has ____ phases: ______, ______and
______.
Initiation
1st – Messenger RNA leaves the ______through a nuclear pore and enters the cytoplasm.
Each tRNA has a series of 3 bases called the ______- that pairs with the
3 ______bases of the mRNA.
tRNA diagram:
______- some tRNA molecules have their 3rd base as a modified form of
adenine called ______which can pair with U, C or A. So there are only 45 kinds of tRNA instead of the expected 61.
2nd – An enzyme called ______is activated by
binding ______and a particular amino acid. (There are 20 kinds of this enzyme, one for
each kind of ______.) The ATP loses 2 P groups and becomes
______. Now the appropriate ______fits into the active site of the enzyme, taking
the place of the ______. Then the enzyme releases the ______with its ______
______.
Diagram:
3rd- The ______were also made in the nucleus in 2 pieces, a large and a
small subunit. These small subunit of the ______now attaches to the
____ end of the ______. A ______RNA carrying the amino acid
methionine attaches to the ______codon of the mRNA. (AUG)
Diagram:
4th - Proteins called ______factors help join the mRNA, tRNA and rRNA
subunits together. The large subunit has 3 sites, the ______(peptidal-tRNA
site),the ______(aminoacyl-tRNA site) and the ______(exit site).
Diagram:
Elongation:
5th - The tRNA with methionine is in the ______of the ribosome. The
ribosome acts as a huge ______, catalyzing the reaction of producing proteins.
The ______of the mRNA in the ______of the ribosome is read.
The tRNA that pairs up with that codon brings its ______and enters
the A site with energy from 2 ______molecules and the help of ______
______proteins.
mRNA: A U G C G A C U A G C A
6th – The ribosome acts as a catalyst to form a ______to attach the amino acid in the P site with the amino acid in the A site.
7th – The tRNA in the ____ site moves into the ______using energy from
______. The tRNA in the ____ site moves to the ____ site and the ____ site is open for
the next tRNA to come. The first tRNA ______.
mRNA: A U G C G A C U A G C A
The movement of the ribosome along the mRNA strand is called ______
8th – The tRNA with the ______for the ______in the A site
brings its ______. ______acting as a ribozyme attaches this amino acid to the other amino acid in the forming chain.
Termination:
Steps repeat until a ______codon is reached. A ______factor protein
attaches to the ____ site. Then the final protein (amino acid chain) is
______and the ribosome parts separate.
Diagram:
Additional information about protein synthesis
One mRNA strand can be used to make ______proteins at the same time, as several
______can be attached at the same time and move along it at different
points. The string of ribosomes doing this is called a ______.
Diagram:
Remember that ribosomes can be ______in the cytoplasm or attached to the ER. Their
location is determined by the ______they are producing. If the protein will be
used in ______or the by endomembrane system, then its amino acid
sequence has a sequence of about 20 amino acids called the ______.
A protein RNA complex called a ______
will recognize the signal peptide and bring the ribosome to a ______protein in the ER to finish protein production there.
Prokaryotes differ from eukaryotes in their protein synthesis in that their ______
and ______are different, eukaryotes need ______,
their transcription is ______differently and prokaryotes can translate and
transcribe the same gene simultaneously because they have no ______.
Mutation
______– a change in the DNA of an organism
A mutation in a ______only affects the cells made when that cell
undergoes ______.
A mutation in a ______will alter _____ the cells in the ______organism’s body.
______– changes just one or a few nucleotides
3 Types of Point Mutation
1. ______– a wrong nucleotide is paired up in _____ place.
Ex. Original DNA New DNA or mRNA strand
G C
A C <------wrong
C G
Can result in ____ wrong ______in the protein that is made from it. The protein may still work or it may not work.
Because several ______code for the same amino acid, the ______amino acid could still be put in.
Ex. C G
C G
C A ß wrong
DNA RNA
But GGG and GGA both code for glycine.
2. ______– one ______nucleotide is added. Because codons are
in 3’s, this changes all the ______down the strand from that point on. (Also
called a ______. )
Protein will be ______.
DNA: G G A C T G C A T
RNA: C G C U G A C G U A
Added
3. ______– one nucleotide pairing is ______.
This also changes all the ______down the strand. Protein will be ______.
DNA: G G A C T G C A T
mRNA: C U G A C G U A
missed
______mutations are DNA mistakes that naturally occur during DNA replication, repair or recombination.
______are substances that cause mutations to occur. Examples include
______, other forms of radiation such as ______light, and ______.
Most ______(chemicals that cause cancer) are ______.