Transcription - RNA Synethesis

Question 1

Why is transcription needed?

Answer 1

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.

Question 2

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

Answer 2

A special sequence of bases called the promoter.

Question 3

2. What is the RNA molecule built up from?

Answer 3

The 4 ribose nucleotides in the nucleoplasm.

They then attach themselves to the bases on the DNA by complementary base pairing.

Question 4

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

Answer 4

One strand of RNA is made.

The DNA strand that is copied is called the template strand. - other strand called non-template strand.

Question 5

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

Answer 5

Strong covalent phosphodiester bonds by the enzyme RNA polymerase.

Question 6

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

Answer 6

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

Question 7

5. What happens at the end of the gene?

Answer 7

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

Question 8

6. Where does the mRNA diffuse out of?

Answer 8

The nucleus through a nuclear pore in the cytoplasm.

There is attaches to ribsomes for translation.

Question 9

6. How far are the ribsomes?

Answer 9

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