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155 Cards in this Set

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An explanation of how proteins are made using the information we find in DNA:
The "Central Dogma of Biology"
What are the two processes that form the Central Dogma of Biology?
1) Transcription
2) Translation
Describe Transcription:
Transcription is when an enzyme called RNA polymerase reads the DNA and synthesizes a complimentary copy made out of RNA
Describe Translation:
Translation is when the information on the RNA is used to synthesize a protein.
What are the two languages that are translated?
the language of nucleic acid info, into amino acid info.
So, transcription and translation are two processes used to make:
proteins
Is RNA double stranded or single stranded?
single stranded
What are some types of RNA?
mRNA (messenger RNA)
rRNA (ribosomal RNA)
tRNA (transfer RNA)
Where does replication start and stop?
What opens the double helix?
What actually copies DNA?
Other enzymes involved?
At the ORI, ends with Ligase.
Helicase opens the helix.
DNA Polymerase III copies.
DNA polymerase I.
Primase (makes RNA primer).
In RNA, which nitrogenous base is different than DNA?
RNA doesn't have T - Thymine, it has U - Uracil instead.
Which is the main RNA made during transcription that is the direct copy from the DNA?
mRNA - messenger RNA
Where does transcription start and stop?
What opens the double helix?
What actually does the copying?
Other enzymes involved?
At the promoter; ends at the termination sequence.
RNA Polymerase unwinds the helix, he doesn't need help.
RNA polymerase copies.
No other enzymes involved
What does tRNA do?
tRNA is involved in the process of translation
What does rRNA do?
rRNA makes up part of the structure of the ribosome
Where does Transcription start & stop?
At the Promoter & Termination Sequence
After transcription all of the _____ goes through translation.
all of the RNA
During translation, the ribosome uses ________ and _________ to make the protein.
mRNA & tRNA
The reading of the DNA and synthesizing of an RNA copy:
Transcription
What enzyme carries out transcription?
RNA polymerase
RNA polymerase reads the DNA and synthesizes a complimentary _____ copy.
a complimentary mRNA copy
Describe how Transcription starts
RNA polymerase starts Transcription at a particular sequence in the DNA called the promoter. He binds to the DNA and unwinds it by himself, he doesn't need Helicase.
RNA polymerase goes through the Transcription process until it reaches a sequence called the___________, where it will fall off the DNA
termination sequence
RNA polymerase copies a complimentary pair, so if it reads the following, what will it copy to the RNA?

A it will put down:
T it will put down:
G it will put down:
C it will put down:
A it will put down: U
T it will put down: A
G it will put down: C
C it will put down: G
During Transcription, DNA is read in groups of three consecutive bases, called___________; these ________ are copied onto mRNA where they are called___________.
DNA is read in groups of three consecutive bases, called TRIPLETS; these Triplets are copied onto mRNA where they are called CODONS.
In Transcription, downstream refers to:
the direction of Transcription, or the 5prime→3prime direction
In Transcription, upstream refers to:
the opposite direction of downstream
The length of the final mRNA molecule depends upon the :
polypeptide that it encodes, an avg. one is about 1,200 nucleotides long.
The Termination Sequence is _______stream from the Promoter.
downstream
Are the Promoter Sequences Transcribed as part of the final mRNA molecule?
NO
RNA polymerase binds to the Promoter __________stream of the gene.
RNA polymerase binds to the Promoter upstream of the gene.
Which direction does RNA Polymerase travel?
RNA Polymerase adds nucleotides complementary to the template strand of DNA in the 5prime → 3prime direction.
Where does replication start and stop?
What opens the double helix?
What actually copies DNA?
Other enzymes involved?
At the ORI, ends with Ligase.
Helicase opens the helix.
DNA Polymerase III copies.
DNA polymerase I.
Primase (makes RNA primer).
The first DNA Triplet to be Transcribed is almost invariably:
TAC, which well be copied to mRNA as the Start Codon, AUG!
Where does transcription start and stop?
What opens the double helix?
What actually does the copying?
Other enzymes involved?
At the promoter; ends at the termination sequence.
RNA Polymerase unwinds the helix, he doesn't need help.
RNA polymerase copies.
No other enzymes involved
Transcription: _________ is used in place of Thymine.
Uracil
Transcription: _________ falls off the DNA and stops transcription at the _________.
RNA Polymerase falls off the DNA and stops transcription at the Terminal Sequence.
The length of DNA that gets copied during Transcription is called the:
Transcription unit
What exactly is the Promoter?
The PROMOTER is a specific region/sequence of DNA located just UPSTREAM of the Gene, that RNA Polymerase binds to.
The base pair rules for RNA are:
C→G
A→U
What exactly is the Termination Sequence?
The TERMINATION sequence is a code on the end of the gene that signals the separation and release of the completed mRNA.
In Translation, the mRNA are not read individually, they are read in ____ nucleotide segments called:
they are read in 3 nucleotide segments called: Codons
Codons are 3 nucleotide chunks of mRNA that encode ___ amino acids?
Codons are 3 nucleotide chunks that encode 1 amino acid
What is the name of the DNA strand that doesn't get copied in Transcription?
the NON-TEMPLATE STRAND
So during translation, the first Codon is read and that is the information for the ____________; the second Codon is read and that is the information for the ____________.
first Codon is read and that is the information for the FIRST AMINO ACID; the second Codon is read and that is the information for the SECOND AMINO ACID.
What unwinds the DNA during transcription?
RNA polymerase does this, he doesn't need any help.
During Translation, ________ interpret the DNA code and translate it into amino acids.
tRNAs - Transfer RNAs
The DNA strand that gets copied during transcription is called the ___________ and the mRNA copy is called the ___________.
template strand; transcript
The DNA strand that does not get copied during transcription is called the ___________
coding strand or non-template strand
During translation, __________ read the mRNA Codons and bring in the correct amino acid.
tRNAs
During translation, the tRNA's ________ binds to the Codon of the mRNA and brings in an __________.
Anticodon; amino acid
What is the start Codon in Translation and which amino acid does it encode?
AUG; Methionine
Which amino acid do all proteins have as their first amino acid?
methionine
What are the three stop codons in Translation?
UGA
UAG
UAA
Are there multiple Codons that encode the same amino acid?
yes, there is some redundancy
Is the translation code universal among organisms?
yes
The site for Translation is the:
ribosome; either on the RER or in the cytoplasm
the ribosome has two subunits:
-Large subunit
-Small subunit
The ribosome is composed of:
both protein & ribosomal RNA (rRNA)
What serves as one of the most important portions of the ribosome in structure and function?
the RNA
What are the two main sites for binding tRNAs?
the P & A sites
Describe the translation process:
1) The ribosome assembles around the mRNA, the small subunit binds to the mRNA and scans looking for the start Codon.
2) Once the small subunit finds the start Codon (AUG), the large subunit attaches.
3) The first tRNA comes in and binds to the P site of the ribosome. The first tRNA's Anticodon (UAC) binds to the start Codon (AUG) of the mRNA and brings in the first amino acid which is of course Methionine.
4) The second Codon lines up with the A site of the ribosome; the second tRNA comes and binds his Anticodon with the Codon of the mRNA that he's lined up with and brings his amino acid.
5) A peptide bond is formed between the amino acids of the P & A sites.
6) The ribosome begins to shift, pulling the mRNA through and discharging the first tRNA through the exit tunnel (E site), leaving the two amino acids connected by the peptide bond. The second tRNA shifts over to the P site.
7) The third tRNA enters the A site, binds his Anticodon to the Codon of the mRNA and establishes a peptide bond to the other tRNA in the P site.
8) This process continues until the ribosome encounters the stop Codon, at which time everything flies apart.
When Translation stops, can the mRNA be used again?
yes, multiple times
What starts & stops DNA Replication?
What starts & stops Transcription?
What starts & stops Translation?
DNA Replication: Starts with the Primer & ends with DNA ligase
Transcription: The Promoter & the Termination Sequence
Translation: The start code: UAG & one of these stop codes: UAA, UAG, UGA
Where does transcription start and stop?
What opens the double helix?
What actually does the copying ?
Other enzymes involved?
At the promoter; ends at the termination sequence.
RNA Polymerase unwinds the helix, he doesn't need help.
RNA polymerase copies.
No other enzymes involved
What are the base pair rules during transcription?
C→G
A→U
Where does replication start and stop?
What opens the double helix?
What actually copies DNA?
Other enzymes involved?
At the ORI, ends with Ligase.
Helicase opens the helix.
DNA Polymerase III copies.
DNA polymerase I.
Primase (makes RNA primer).
Can mRNA be re-used again by the ribosome to make protein?
yes, multiple times.
In prokaryotes, can translation start before transcription is finished?

What about in Eukaryotes?
In prokaryotes yes, in Eukaryotes no.
Can transcription and translation occur at the same time in a Eukaryote?
no, because the DNA in a Euk is in the nucleus, and the ribosomes are outside of the nucleus.
In a Eukaryote, where does Transcription take place? Where does Translation take place?
In a Eukaryote, Transcription takes place in the nucleus; Translation takes place in the cytoplasm.
In a Prokaryote, where do Transcription and Translation take place?
In a Prokaryote, both Transcription and Translation take place in the cytoplasm. (Proks don't have organelles, duh)
So what are the two reasons that Eukaryotes cannot conduct Transcription & Translation at the same time?
Because the locations for each process don't allow it and because Introns need to be spliced before translation occurs.
non-coding sections of DNA are called:
Introns
Coding section of DNA are called:
Exons
Do introns and exons get copied onto the mRNA? How does this effect translation?
yes, and ∴the mRNA has to be spliced before leaving the nucleus
The process in Euks whereby a special enzyme removes the Introns and sticks the Exons together is called:

Where is this done and in what process.
splicing;

Splicing is done before the mRNA leaves the nucleus so the process is Transcription.
Do prokaryotes have Introns?
no
Extra processing step during transcription in Euks, that doesn't happen in Proks.
splicing out introns and gluing exons together
A change in the sequence of DNA, a change in the genetic material:
Example:
Mutation

For example: a G nucleotide where a C should be.
Do Proks have introns?
No, in Proks all the DNA is coding.
Type of mutations that occur constantly in the DNA of all organisms:
Spontaneous Mutation
Things that drastically increase the frequency of mutations are called:
Mutagens
What are some examples of things that act as mutagens?
-Various Chemicals: asbestos, acrylamide
- UV light & radiation
Most mutations can be attributed to:
a problem with DNA Polymerase lll making a mistake.
Why are mutations so detrimental to the cell?
Because they cause proteins to be made incorrectly. Mutations change the nucleotide sequence of the DNA, thereby affecting transcription, translation, and protein synthesis.
What are the two main types of mutations?
-Substitution mutations &
-Frameshift mutations.
A Substitution mutation is when:
you replace one nitrogenous base with another; one is wrong.
illustrate the steps of how a substitution mutation causes protein synthesis mistakes:
A mutation in the DNA sequence gets copied by the mRNA, the mRNA copy affects the Codon, the incorrect Codon could lead to a different amino acid getting encoded during Translation or to a stop codon being produced.
Describe a Missense mutation:
A missense mutation is a type of Substitution mutation where an incorrect nucleotide causes a different amino acid to be encoded.
Describe a Nonsense Mutation:
A Nonsense Mutation is a type of Substitution mutation where an incorrect nucleotide causes a stop Codon to be inadvertantly made.
What are the two types of Frameshift mutations?
-Insertion or
-Deletion
Describe an Insertion Mutation:
An Insertion mutation is a type of Frameshift mutation where an extra nucleotide is added affecting all codons after it.
Describe a Deletion Mutation:
A Deletion Mutation is a type of Frameshift mutation where a nucleotide is deleted, affecting all codons after it.
In general, which type of Mutation is more detrimental to the protein's function, Substitution or Frameshift?
In general, Frameshift mutations are more detrimental.
Describe a Silent Mutation:
A Silent Mutation is a type of Substitution Mutation where a nucleotide is changed, but because of Redundancy, the correct amino acid is produced anyway.
Mutations are occurring constantly, largely because of mistakes by:
DNA Polymerase lll
These enzymes find and repair mutations in the DNA:
Excision Repair Enzymes
Describe how Excision Repair Enzymes fix DNA:
The Excision Repair Enzymes cut out the mutated DNA and then DNA Polymerase l comes and fill in the correct DNA, Ligase comes and fills in the gaps.
A genetic disease where patients don't have Excision Repair Enzymes, which makes the mutation causing affects of sunlight deadly to them.
Xeroderma pigmentosa
A coordinated set of genes, all of which are regulated as a single unit.
Prokaryotic Operons
Do Eukaryotes have Operons?
No, only Prokaryotes have Operons.
What are the two types of Operons?
Inducible & Repressible
Describe an Operons function:
A bacteria that wants to digest maltose, it needs several enzymes. It needs to make all the enzymes (making just one would not be beneficial; all or none), so the Prokaryote puts the genes for ALL those enzymes together under ONE PROMOTER and regulates them all together. They will ALL be Transcribed & Translated together or NONE will be Transcribed & Translated.
Type of Operon where Transcription is normally off, but the Operon is turned ON by substrate.
Inducible Operon
Type of Operon where Transcription is normally on, but the Operon is turned OFF by the product synthesized.
Repressible Operon
Where does replication start and stop?
What opens the double helix?
What actually copies DNA?
Other enzymes involved?
At the ORI, ends with Ligase.
Helicase opens the helix.
DNA Polymerase III copies.
DNA polymerase I.
Primase (makes RNA primer).
The quintessential example of an Operon is:
the LAC Operon
Where does transcription start and stop?
What opens the double helix?
What actually does the copying?
Other enzymes involved?
At the promoter; ends at the termination sequence.
RNA Polymerase unwinds the helix, he doesn't need help.
RNA polymerase copies.
The Lac Operon's genes contain the enzymes needed to catabolize:
Lactose
In the Lac Operon, Transcription is normally ________, Lactose turns Transcription from the Operon ________, meaning Lac is an ___________ Operon.
In the Lac Operon, Transcription is normally OFF, Lactose turns Transcription from the Operon ON, meaning Lac is an Inducible Operon.
What are the parts of the Lac Operon?
Promoter
Operator
Structural Genes
Regulatory Gene
Repressor
Inducer
The Promoter is the binding site for:
RNA Polymerase, the enzyme that does Transcription; where Transcription starts.
In the Lac Operon, the promoter is next to the:
Operator
a control site that regulates access to the Promoter; turns on or off Transcription.
the Operator
These encode the enzymes needed to digest lactose in the Lac Operon:
How many?
the structural genes; 3 are shown in the diagram.
Elsewhere in the genome, not connected to the Operon but is separate somewhere else in the DNA; encodes a protein called the Repressor.
Regulatory Gene
The Lac Repressor is synthesized in its ______________ form.
active form.
The Transcriptional default for the Lac Operon is _________.
Off
Repressors, when they are active, bind to:
Operators
Is the Regulatory Gene connected to the Operon?
no, it is separate; elsewhere in the genome.
The Repressor is a protein that is encoded by:
the Regulatory Gene
An active Repressor binds to an:
Operator.
Active Repressors bind to:
Operators
Describe the process of the Lac Operon in the absence of Lactose.
the Repressor binds to the Operator, so when RNA Polymerase binds to the Promoter, he physically can't do Transcription because the Repressor is in his way.
The Transcriptional default of the Lac Operon is:
Off
What needs to take place for the Lac Operon to turn on?
Lactose
Lactose acts as the __________ and ____________ the Repressor, which turns Transcription _______.
Lactose acts as the INDUCER and INACTIVATES the Repressor, which turns Transcription ON.
Where does replication start and stop?
What opens the double helix?
What actually copies DNA?
Other enzymes involved?
At the ORI, ends with Ligase.
Helicase opens the helix.
DNA Polymerase III copies.
DNA polymerase I.
Primase (makes RNA primer).
How does Lactose actually Inactivate the Repressor?
Lactose binds to the Repressor and Inactivates it so it falls off the Operator.
Where does transcription start and stop?
What opens the double helix?
What actually does the copying?
Other enzymes involved?
At the promoter; ends at the termination sequence.
RNA Polymerase unwinds the helix, he doesn't need help.
RNA polymerase copies.
Inducers ____________ Repressors.
Inducers INACTIVATE Repressors.
Describe the process of the Lac Operon in the presence of Lactose.
Lactose (the Inducer) binds to the Repressor and Inactivates him, causing him to fall off. Now RNA Polymerase is no longer blocked by the Repressor and can complete Transcription.
In the Lac Operon, Lactose is the _____________ and ____________ the _____________.
In the Lac Operon, Lactose is the INDUCER and INACTIVATES the REPRESSOR.
Describe why the Lac Operon is referred to as Inducible?
Because it is normally OFF, but can be turned ON, or INDUCED by the Inducer (Lactose) to produce enzymes.
So why does the Lac Operon exist?
To increase efficiency and prevent waste of energy; why make enzymes to digest Lactose if no Lactose is present?
So when is the Lac Operon ON?
The Lac Operon in ON in the presence of Lactose.
Repressor active = Lac Operon ____.
OFF
Lactose present = Repressor __________.
Inactivated
What do the Structural Genes do?
they provide transcript info for RNA Polymerase to Transcribe, leading to the Translation of Lactose digestive enzymes.
Repressor Inactivated = Lac Operon ____.
ON
No Lactose present = Repressor ____________ and Lac Operon _____.
No Lactose present = Repressor Activated and Lac Operon OFF.
Do Eukaryotes have Operons?
NO!
Does the Lac Operon function in the presence of Glucose?
NO, the Prok prefers Glucose.
What do the Structural Genes do in the Arginine Operon?
They contain the info for the Transcription of enzymes needed to synthesize the amino acid Arginine.
Why is Arginine important?
Arginine is 1 of the 20 amino acids that ALL cells need in order to make proteins; ALL cells MUST have Arginine to make proteins.
Because Arginine is so vital to protein production, Normally the Arginine Operon is_________?
On
In the Arginine Operon, the Repressor's default is:
Inactive
The Transcriptional default of the Arginine Operon is __________?
ON
In the Arginine Operon, Arginine is a __________, which __________ the Repressor, turning Transcription ____.
Arginine is a Corepressor, which Activates the Repressor, turning Transcription OFF.
The Arginine Operon is ___________.
Repressible
The Arginine Operon Repressor is synthesized in its ___________ form.
The Arginine Operon Repressor is synthesized in its INACTIVE form.
Corepressors bind to and ____________ the Repressor.
ACTIVATE
In the Arginine Operon, Repressor is to INACTIVE as Transcription is to:
ON
In the Arginine Operon, Transcription is to OFF as Repressor is to:
Active
The default for the Arg Repressor is:
Inactive