RNA Structure, Transcription And Translation Flashcards
What differentiates a heart cell from a liver cell or any other cell?
Gene expression
Every somatic cell in the body has the same genetic information. True or false?
True
How do cells use genetic information?
Cells use the same genetic information in different ways to have different shapes and functions
What is transcription?
This is the process of copying one strand of dna into rna
Where does transcription occur?
In the nucleus
During what phase of cell division does transcription occur mostly?
Interphase
What are the three major ways in which rna differs from dna?
RNA has ribose as sugar
Uracil replaces thymine as a base in rna
Rna is single stranded in structure
In what structure can rna fold and bind onto itself taking on double stranded characteristics?
Secondary structure
What structure is important for rna integrity and function?
Secondary structure.
(Messenger) MRNA comes about as a result of?
Transcription.
What is mRNA?
It is messenger rna, a template for translation of protein
What RNA type is part of the ribosomal complex?
rRNA
What is rRNA?
It is RNA that controls recognition between mRNA codon and tRNA anticodon during translation
This RNA’s function is to control recognition between codon of mRNA and anticodon of tRNA
rRNA
What is tRNA’s structure?
tRNAhas a cloverleaf secondary structure
What is the function of tRNA?
It carries amino acid to correct location on mRNA template to form protein
This RNA carries amino acid to correct location on mRNA template to form a protein
tRNA
In what direction does transcription occur?
5’ - 3’
What is the term given to RNA synthesis?
Transcription
What is RNA polymerase?
This is the enzyme that catalyzes RNA synthesis
What are the things required for RNA synthesis? (Transcription)
RNA polymerase
DNA template (anti-sense strand)
Ribonucleoside triphosphates
Transcription factors
What is DNA template?
Antisense of DNA
What is the sense strand?
The DNA coding strand
In terms of what is DNA sequence always written?
In terms of sense strand (5’ - 3’)
Why is the sense strand also called the coding strand?
Because you can predict the amino acid sequence directly from it
What is the mRNA sequence?
It is the same sequence as the DNA sense strand except thymine replaced with uracil
What is the antisense strand?
It is the strand that is complementary and antiparallel to the sense strand (3’ - 5’), which serves as the template for mRNA synthesis
What is another name for the antisense strand?
Template strand
This strand serves as the template for mRNA synthesis.
Antisense strand
What is the upstream and downstream part of a sequence?
5’ and 3’ end respectively in reference to a sense strand
What is the transcription start site designated?
+1
What numbers are the bases upstream given?
Negative numbers
What are the three phases of transcription?
Initiation
Elongation
Termination
What us found upstream of the coding region of a gene?
A promoter region
What are promoters?
They’re short consensus sequences
List the DNA sequences collectively known as promoters?
TATA box (TATAA) -30 to -100 GC box (GGGCGG) -40 to -150 CAAT box (CCAAT) -40 to -150
What do transcription factors bind to in order to initiate transcription?
Promoters
How do promoters help in initiating transcription?
Through binding with transcription factors (proteins)
What other sequence elements can direct transcription?
Enhancers
Silencers
Hormone response elements
What initiates transcription?
The binding of RNA polymerase and transcription factors to promoters
What happens after initiation?
Elongation
What happens during elongation?
RNA polymerase moves along the DNA and incorporates rNTPs in the growing RNA chain in the 5’ to 3’ direction
What happens in transcription termination?
Transcription of the growing RNA chain continues in the 5’ to 3’direction until RNA polymerase recognizes a sequence signal that signals the end
What is the termination sequence?
AAUAAA
Where is the termination signal located?
In the 3’ UTR (untranslated region) of the gene
What happens after RN polymerase recognizes the termination sequence AAUAAA in the 3’ UTR?
The immature mRNA goes through processing
What are the three steps of mRNA processing?
Capping
Polyadenylation
RNA splicing
For what reasons is the 5’ end of the growing primary transcript capped?
For functional and protective reasons
What ends are joined during capping of mRNA?
7-methylguanine is joined to the 5’ nucleotide
Termination of transcription upon the recognition of the sequence AAUAAAresukts in what?
In the cleavage of the 3’ end of the primary transcript
What is then added on the 3’ end after cleavage?
The enzyme poly(A)polymerase adds a repeated sequence of Aden,ate (A) residues on the 3’ end
What purpose does the repeated sequence of adenylate (A) residues added by the poly(A)polymerase on the 3’ end serve?
To protect the mRNA and designate it as mature mRNA which can be recognized by ribosomes for translation
What two areas are found on DNA?
Exxon’s and introns
The coding region of most eukaryotic genes contains what two regions?
Translated and untranslated regions
What are introns?
These are regions that interrupt the coding sequence, do not code for protein, and are not part of the mature mRNA
What are Exons?
Exons include the coding sequence (open reading frame) and some untranslated, regulatory regions (UTR)
This part of DNA interrupts coding sequence, does not code for protein and is not part of a mature mRNA.
Intrins
This part of DNA includes the coding sequence and some untranslated regulatory regions
Exons
What is RNA splicing?
Thus us a series of reactions where the intron sequences are snipped out and the exon sequences are joined from end-to-end (spliced)
What is the term given to removal of introns?
Splicing
What designates the intron-exon boundaries?
Some conserved sequences
Where does splicing out occur?
In the spliceosome
What is the spliceosome?
Thus is a unit of proteins and small nuclear RNA where splicing occurs
What is alternative splicing?
This is when one gene results in several different proteins because of different Exon combinations that resulted after splicing
List the things found on a mature mRNA after splicing.
5’ cap
Exons joined
Poly(A) train on 3’ end
What two exons are not translated?
5’ UTR
3’ UTR
What happens to the mature mRNA when transcription terminates?
It is exported out of the nucleus into the cytoplasm in preparation for translation.
What is translation?
This is the conversion of mRNA message into protein
Where does translation take place?
On ribosomes
What serves as an adaptor molecule for converting the mRNA message into an amino acid (protein) sequence?
tRNA
All the information necessary to synthesize a cell’s protein is contained in?
The DNA
What is protein made of?
A series of amino acids
How many bases and amino acids are there?
There are only 4 bases but 20 amino acids
A sequence of how many bases is used during translation?
A sequence of 3 bases
How many combinations of triplicate bases are possible?
64 possible combinations
What is the codon?
This is the triplicate of bases
What us the term given to the the triplicate of bases formed for translation?
Codon
Each codon specifies what two things?
Either an amino acid or a stop signal
How many codons are designated in an amino acid?
Most amino acids are designated by more than one codon
How is a protein’s primary sequence read on the mRNA?
5’ to 3’
What is the size of a tRNA?
They’re small molecules of about 70-95 nt
What does one loop of a tRNA contain?
Anticodon which is complement to the codon on the mRNA
What does the other end of a tRNA contain?
A CCA sequence which binds and carries the appropriate amino acids
Where does translation occur in eukaryotes?
In the cytoplasm on the ribosomes
What are ribosomes?
They’re complexes of proteins and RNA
How many ribosomal proteins are found in the Large 60Ssubunit?
~50 ribosomal proteins
How many ribosomal proteins are found in the Smaller 40S subunit?
~30 ribosomal proteins
How does translation start?
Special proteins recognize the 5’ cap and poly-A tail of mRNA so they recruit ribosomal subunits
What happens after special proteins recognize the 5’ cap and poly(A) tail of the mRNA?
Pre-initiation complex scans for AUG start codon
What us the AUG start codon?
Methionine
Describe the structure of the ribosome.
The ribosome has 2 functional sites; the P-site (peptidyl) and A-site (aminoacyl), and a third E-site (exit)
Pre initiation complex scans for what in the mRNA?
AUG start codon (methionine)
What happens during elongation and termination in translation?
Peptide bond is formed between adjacent amino acids, process which continues until stop codon is reached, and release factors detach polypeptide from tRNA, and ribosome disassembles.
