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What are proteins?
Polypeptides made up of amino acids.
How are Amino Acids linked?
By peptide bonds.
What is Gene Expression
It is the process by which DNA directs the synthesis of proteins.
How many stages are included in Gene Expression?
Two
What are the two stages of Gene Expression?
Transcription and Translation.
How many organisms does Gene Expression occur in?
It occurs in all of them.
What is Transcription?
It is the synthesis of RNA using information from DNA.
What allows for the “message” of the DNA to be transcribed?
Transcription.
Where does Transcription occur?
It occurs in the nucleus.
What is Translation?
It is the synthesis of a polypeptide using the information from RNA.
Where does Translation occur?
At the ribosome.
What happens to a nucleotide sequence in Translation?
It becomes an amino acid sequence.
How many types of RNA molecules are there when you go through transcription and translation?
There are three types.
What are the three types of RNA molecules?
Messenger RNA, Ribosomal RNA, and Transfer RNA.
When is Messenger RNA synthesized?
During Transcription using a DNA template.
What does Messenger RNA do?
It carries information from the DNA (at the nucleus) to the ribosomes in the cytoplasm.
What can each Transfer RNA carry?
A specific amino acid.
How can Transfer RNA attach to Messenger RNA?
Via their Anticodon.
What is an Anticodon?
A complementary codon to Messenger RNA.
What does Transfer RNA’s Anticodon allow for?
Information to be translated into a peptide sequence.
What does Ribosomal RNA help form?
Ribosomes.
What does Ribosomal RNA help link?
Amino Acids.
Where is the sequence of nucleotides that code for proteins contained?
In DNA.
How is the sequence of nucleotides that code for proteins read?
In groups of three called the Triplet Code.
How many strands of DNA are transcribed during Transcription?
One.
What is the one strand of DNA that is transcribed during Transcription called?
It is known as the template strand (and the noncoding strand, minus stand, or antisense strand).
What is antiparallel and complementary to the DNA nucleotides?
mRNA molecules.
What is the Base Pairing in Genetic Code?
Adenine with Uracil and Cytosine with Guanine.
What are the mRNA nucleotide triplets called?
Codons.
What codes for Amino Acids?
Codons.
How many different codon combinations are there?
64.
How many of the codon combinations code for amino acids?
61.
How many of the Codon Combinations are Stop Codons?
3.
What is Redundancy?
When more than one codon codes for each amino acid.
What is Reading Frame?
When the codons on the mRNA must be read in the correct groupings during translation to synthesize the correct proteins.
What will happen if the reading frame shifts even by one letter?
It will produce a completely different outcome.
If the DNA template strand reads 3’-ACGAGA- 5’ what will the mRNA transcript read?
5’- UGCUCU-3’.
What are the three steps in Transcription?
Initiation
Elongation
Termination
When does Transcription begin?
When RNA polymerase molecules attach to a promoter region of DNA.
Does Transcription need a primer to attach to DNA?
No.
Where are the Promoter Regions in DNA?
They are upstream of the desired gene to transcribe.
What is the Promoter Region called in Eukaryotes?
TATA Box.
What do Transcription factors help with in Eukaryotes?
They help RNA Polymerase bind.
What opens the DNA and reads the triplet code of the template strand?
RNA Polymerase.
What directions does RNA Polymerase move along the DNA?
In the 3’ to 5’ direction.
What direction does the mRNA transcript elongate?
In the 5’ to 3’ direction.
Does RNA Polymerase move upstream or downstream?
Downstream.
Does RNA Polymerase open large or small sections of DNA at a time?
Small sections.
What does RNA Polymerase pair?
Complementary RNA Nucleotides.
What happens to the growing mRNA strand?
It peels away from the DNA template strand.
What happens after the mRNA strand peels away from the DNA template strand?
DNA double helix reforms.
How many RNA Polymerase Molecules can transcribe a single gene?
Several RNA Polymerase Molecules can transcribe a single gene simultaneously.
What helps increase the amount of mRNA synthesized and increases protein production?
The fact that a single gene can be transcribed by several RNA Polymerase Molecules.
How does transcription proceed in Prokaryotes?
Through a Termination Sequence.
What causes a Termination signal?
The Termination Sequence.
What happens to RNA Polymerase during transcription in Prokaryotes?
RNA Polymerase detaches.
What happens to mRNA transcript during transcription in Prokaryotes?
It is released and proceeds to translation.
During Transcription in Prokaryotes, what changes does mRNA need?
It does not need any changes.
What is the sequence of DNA that is transcribed by RNA Polymerase in Eukaryotes called?
It is called the Polyadenylation Signal Sequence.
What does the Polyadenylation Signal Sequence code for?
A polyadenylation signal (AAUAAA).
What does a polyadenylation signal do?
It releases the pre-mRNA from the DNA which must undergo modifications before translation.
What are the three modifications that must occur to eukaryotic pre-mRNA before it is ready for translation?
5’ Cap
Poly-A Tail
RNA Splicing
What is the 5’ Cap (GTP) modification?
The 5’ end of the pre-mRNA receives a modified guanine nucleotide “cap”.
What is the Poly-A Tail modification?
The 3’ end of the pre-mRNA receives 50-250 adenine nucleotides.
What three things do both the 5’ Cap and the Poly-A Tail modifications function to do?
They help the mature mRNA leave the nucleus.
They help protect the mRNA from degradation.
They help ribosomes attach to the 5’ end of the mRNA when it reaches the cytoplasm.
What does the RNA Splicing modification do?
It removes sections of the pre-mRNA, called introns, and then joins exons together.
What are Introns?
There are intervening the sequence and they do not code for amino acids.
What are Exons?
They are expressed sections and they code for amino acids.
Why does RNA Splicing occur?
Because a single gene can code for more than one kind of polypeptide.
What is it called when a single gene can code for more than one kind of polypeptide?
Alternative Splicing.
When is Pre-mRNA considered Mature mRNA?
Once all modifications have occurred.
What happens when mRNA becomes Mature?
It can leave the nucleus and proceed to the cytoplasm for translation at the ribosomes.
What is the “Big Picture” of transcription?
It writes down information from the DNA and allows it to leave the nucleus to be translated into a protein.
How is initiation different in Eukaryotes and Prokaryotes?
Eukaryotes need transcription factors to help RNA Polymerase bind to the DNA, while Prokaryotic RNA Polymerase can bind directly to the DNA.
What is Translation?
The synthesis of a polypeptide using information from the mRNA.
Where does Translation occur?
At the Ribosome.
What does Translation do to a nucleotide sequence.
It becomes an amino acid.
What is a key player in translating mRNA to an amino acid sequence?
tRNA.
What is tRNA’s Anticodon region complementary and antiparallel to?
mRNA.
tRNA carries the amino acid for what?
For the mRNA codon to code for.
What codes for the amino acid Threonine ?
ACU.
What is responsible for attaching amino acids to tRNA?
The enzyme aminoacyl-tRNA synthetase.
When is a tRNA “charged”?
When it carried an amino acid.
How many subunits do Ribosomes have?
Two, a small and a large.
How do Prokaryote and Eukaryote ribosomal subunits differ in size?
Prokaryotes small subunit is 30s and the large is 40s where as Eukaryotes small subunit is 40s and its large is 60s.
How many sites does a large ribosome subunit have and what are they called?
They have three called A, P, and E.
What is the “A” site in a large ribosome subunit?
An amino acid site that holds the next rRNA carrying an amino acid.
What is the “P” site in a large ribosome subunit?
A polypeptide site that holds the rRNA carrying the growing polypeptide chain.
What is the “E” site in a large ribosome subunit?
An exit site.
How does the tRNA interact with the mRNA?
Through its Anticodon.
How many stages does Translation occur in?
Three.
What are the three stages of Translation?
Initiation
Elongation
Termination
How does Translation begin?
When the small ribosomal subunit binds to the mRNA and a charged tRNA binds to the start codon (AUG) on the mRNA.
What does the tRNA carry at the start of Translation?
It carries Methionine.
Where does the first tRNA carrying Methionine always go and where to the other tRNA go?
The first one goes to the P site and the rest go to the A site.
When does Elongation start?
When the nest tRNA comes into the A site.
What happens to mRNA during Elongation?
It is moved through the ribosome and its codons are read.
What do each individual mRNA codon code for?
Their own specific amino acid.
What is used to determine the amino acid that an mRNA codon codes for?
A Codon Chart.
What supports the idea of “Common Ancestry”?
Since all organisms use the same genetic code.
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