LAB 4 GENE EXPRESSION pg.66 Flashcards
What is gene expression?
The process of transcription and translation
What is transcription?
The process of making mRNA from DNA
What is translation?
The decoding of an mRNA message into a protein
How does DNA aid cellular activities?
The DNA is transcribed into mRNA, sent out of the nucleus into the cytoplasm. Ribosome translates the mRNA
The direction of the template strand…
Is always 3’ to 5’
The direction of the coding strand…
Is always 5’ to 3’
The mRNA formed during translation…
It is the same as the coding strand, opposite to the template strand. It has Uracil in place of Thymine.
The direction of translation…
Is always 5’ to 3’
The direction of transcription…
Is always 5’ to 3’
What happens during DNA transcription initiation?
The TATA box located in the promoter region of the DNA is recognized by transcription factors, allowing them to assemble and, eventually, RNA polymerase to bind.
Once the RNA polymerase is bound, it will separate the coding and template strands and start transcribing across the strand with complementary bases.
What happens during DNA transcription elongation?
RNA polymerase “walks” across the template strand in the 3’ to 5’ direction, synthesizing RNA in the 5’ to 3’ direction with complementary base pairings of nucleotides.
What happens during DNA transcription termination?
The polymerase will transcribe a termination sequence, causing pre-mRNA to be cut by an enzyme and released from the polymerase. The polymerase falls off the DNA eventually.
What happens during mRNA processing?
The pre-mRNA is processed to form mRNAs.
The 5’ end is capped, and a 3’ poly-A tail is added to the 3’ end. This ensures stability.
They then undergo a splicing process, where introns are chopped out, and exons are kept. This ensures the correct sequence is made.
The mature mRNA then travels across the nuclear membrane into the cytoplasm to be translated.
What happens during mRNA translation initiation?
The tRNA carrying methionine attaches to the small ribosomal subunit; they both bind to the 5’ end of the mRNA by recognizing the 5’ cap.
They then walk along in the 3’ direction until they find a start codon.
The tRNA binds to the start codon via their anticodon, and the large ribosomal subunit joins and binds the tRNA in its P site.
