DNA, RNA and protein synthesis: Transcription and translation Flashcards
1
Q
What are the two processes of protein synthesis
A
- Transcription
- Translation
2
Q
Where does transcription occur in prokaryotes
A
The cytoplasm
3
Q
Where does transcription take place in eukaryotic cells
A
The nucleus
4
Q
What is the first process in protein synthesis
A
Transcription
5
Q
What is the second process in protein synthesis
A
Translation
6
Q
Describe the process of transcription
A
- RNA polymerase attaches to DNA at the beginning of a gene
- In eukaryotes, the hydrogen bonds between the two DNA strands (in the double helix) is broken by a DNA helicase attached to RNA polymerase
- This separates and uncoils the DNA molecule, exposing some of the bases
- Then on of the DNA strands (that was uncoiled) is used as a template to make an mRNA copy
- RNA polymerase lines up free RNA nucleotides along exposed bases on template strand. The free bases are attracted to the exposed bases and they attach to their complimentary base
- Once attached, they are joined together by RNA polymerase, forming an mRNA molecule
- RNA polymerase moves along DNA, separating the strands and assembling the mRNA strand
- Hydrogen bonds reform once RNA polymerase has passed and coils back into double helix
- When RNA reaches a stop signal, it stops making mRNA and detaches
- mRNA moves out of nucleus through nuclear pore and attaches to ribosome
7
Q
What is splicing
A
- When introns from pre-mRNA are removed and the exons are joined together - creating mRNA
8
Q
When and where does splicing occur
A
It occurs in the nucleus, after transcription (and before translation)
9
Q
What occurs after splicing to enable translation to occur
A
The mRNA leaves the nucleus
10
Q
Why does splicing not occur in prokaryotes
A
- Bc mRNA is produced directly from the DNA, as there are no introns in prokaryotic DNA
11
Q
What is made when pre-mRNA undergoes splicing
A
mRNA
