Transcription - RNA Synethesis Flashcards Preview

DNA, RNA and Protein Synthesis - Biology - Alevel > Transcription - RNA Synethesis > Flashcards

Flashcards in Transcription - RNA Synethesis Deck (9)
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Why is transcription needed?

DNA never leaves the nucleus, and the proteins are synethesised in the cytoplasm, so a copy of a gene is made to carry the 'message' from the nucleus to the cytoplasm.
The copy is mRNA.


1. The start of each gene on the DNA is marked by what?

A special sequence of bases called the promoter.


2. What is the RNA molecule built up from?

The 4 ribose nucleotides in the nucleoplasm.
They then attach themselves to the bases on the DNA by complementary base pairing.


2. How many strands are made and what is the strand that is copied called?

One strand of RNA is made.
The DNA strand that is copied is called the template strand. - other strand called non-template strand.


3. What are the new nucleotides joined to each other by?

Strong covalent phosphodiester bonds by the enzyme RNA polymerase.


4. How many base pairs remain attached at a time?

8, since the mRNA molecule peels off from the DNA as it is made.
Winding enzyme rewinds the DNA.


5. What happens at the end of the gene?

The transcription stops, mRNA molecule is just the length of the gene.


6. Where does the mRNA diffuse out of?

The nucleus through a nuclear pore in the cytoplasm.
There is attaches to ribsomes for translation.


6. How far are the ribsomes?

Usually not far as many are attached to the rough endoplasmic reticulum.