Polypeptide Synthesis - Transcription And Splicing

Question 1

What is transcription

Answer 1

Process of making pre-mRNA using part of the DNA template

Question 2

Describe transcription

Answer 2

1. RNA polymerase attaches to the DNA double helix at the beginning of the gene
2. The hydrogen bonds between the two DNA strands break, separating the strands, and the DNA molecule uncoils at that point, exposing some of the bases
3. One of the strands is then used as a template to make an mRNA copy
4. The RNA polymerase lines up Free RNA nucleotides alongside the exposed bases on the template strand. The free bases are attracted to the exposed bases ( specific complimentary base pairing means that the mRNA strands ends up being complementary copy of the DNA template strand (except T is replaced with U) )
5. Once they have paired up to there specific bases on the DNA strand, they’re joined together by RNA polymerase, forming a mRNA molecule
6. RNA polymerase moves along the DNA, separating the strands and assembling the mRNA strand
7. The hydrogen bonds between the uncoiled strands of DNA reform once the RNA polymerase has passed by and the strands coil back into a double helix
8. When RNA polymerase reaches a particular sequence of DNA called a stop signal, it stops making mRNA and detached from the DNA
9. mRNA moves out of the nucleus through a nuclear pores and attaches to a ribosome in the cytoplasm

Question 3

What is splicing. Where does it take place

Answer 3

In eukaryotes, introns are removed and the Exons join together - forming mRNA strands. This takes places in the nucleus. The mRNA then leaves the nucleus for the next stage of protein synthesis