PRE FI LEC 1: TRANSCRIPTION AND TRANSLATION Flashcards
A cell uses 2 processes to manufacture proteins using genetic instructions which are…
TRANSCRIPTION AND TRANSLATION
- Synthesis of RNA molecule that is complementary to 1 strand of the DNA double helix for a particular gene (DNA to RNA)
- copies DNA information into RNA.
TRANSCRIPTION
Uses the information in the RNA to manufacture a protein by aligning & joining specified amino acids (RNA to proteins)
TRANSLATION
Bridges gene and protein
RNA
Bases of RNA sequence is complementary to the strand of double helix which we called________
TEMPLATE STRAND
3 MAJOR TYPES OF RNA
- MESSENGER RNA (mRNA)
- RIBOSOMAL RNA (rRNA)
- TRANSFER RNA (tRNA)
- CARRIES A PARTICULAR INFORMATION that specifies a particular protein
- Each 3 mRNA bases in a row form a genetic code word called ______
- 500 -4500 bases long
- ENCODE AMINO ACID SEQUENCE
MESSENGER RNA (mRNA)
- Each 3 mRNA bases in a row form a genetic code word called CODON
- 100 to nearly 3,000 nucleotides long.
- Largest component of cellular RNA (80% - 90%)
- ASSOCIATE WITH CERTAIN PROTEINS to form a ribosome, (which structurally support and catalyze protein synthesis)
- Some catalyze the formation of the peptide bonds between amino acids (ribozyme)
- Some help align the ribosome and mRNA
RIBOSOMAL RNA (rRNA)
- BINDS AN mRNA CODON at one end and a specific amino acid at the other.
- Is only 75 to 80 nucleotides long
- One loop of it has 3 bases in a row that form the anticodon
- tRNA with a particular anticodon strongly bonds to a specific amino acid
TRANSFER RNA (tRNA)
One loop of the tRNA has 3 bases in a row that form the __________, which is complementary to an mRNA codon.
ANTICODON
STEPS OF TRANSCRIPTION
- INITIATION
- ELONGATION
- TERMINATION
STEPS OF TRANSCRIPTION
- beginning of transcription, when RNA polymerase & supporting proteins bind to the promoter
- RNA polymerase & its supporting accessory proteins assembled on DNA at a specific site (promoter)
- Control point that determines which genes are transcribed
INITIATION
a special sequence that signals the start of the gene, like a capital letter at the start of a sentence.
PROMOTER
STEPS OF TRANSCRIPTION
- addition of nucleotides to the mRNA strand
- enzymes unwind the DNA double helix locally
- RNA polymerase moves along the DNA strand, adding complementary nucleotides as dictated by the DNA template
ELONGATION
STEPS OF TRANSCRIPTION
- ending transcription, occurs when RNA polymerase crosses a stop (termination) sequence in the gene
- Ending of transcription & happens once the RNA polymerase transcribes a sequence
TERMINATION
a __________ will signal the end of transcription
TERMINATOR SEQUENCE
SETTING THE STAGE FOR TRANSCRIPTION TO BEGIN:
- DNA must be released locally from histones & the helix unwound, involve the participation of:
- DNA - BINDING PROTEINS
- HISTONE MODIFICATION ENZYMES
- RNA POLYMERASE
- TRANSCRIPTION FACTORS
1st transcription factor to bind
TATA BINDING PROTEINS
TATA BINDING PROTEINS is chemically attracted to ___________ which is the BASE SEQUENCE TATA surrounded by long stretches of G and C
TATA BOX
- Many identical copies of RNA are transcribed simultaneously
- Usually ___________ DNA bases lies between RNA polymerase
100 OR MORE
In eukaryotes, the newly made RNA ( primary transcript/pre - mRNA) is further processed before it is functional
mRNA PROCESSING
mRNA PROCESSING STEPS
- CAPPING
- POLYADENYLATION
- SPLICING
a cap blocs the eukaryotic mRNA at the 5’ terminu
CAPPING
ADDITION OF ADENOSINES to the 3’ end of mRNA with the help of polyadenylate polymerase enzyme
POLYADENYLATION
removal of intron (non-coding/intervening) sequences from mRNA
SPLICING
- Assembles a protein using the information in the mRNA sequence
- Particular mRNA codons corresponds to particular amino acids (genetic code)
- Takes place in the free ribosomes in the cytoplasm & in the ribosomes that are embedded in the endoplasmic reticulum
TRANSLATION