Chapter 4 - Protein Synthesis Flashcards
What is the genetic code?
- The specific order of nitrogen bases
- It is read by the cell and produces structural and functional proteins for use by the cell or the organism
- organised into genes and codes for a specific protein
What is gene expression?
Reading one gene at a time. It is the process of using one genetic code to synthesise specific proteins.
How are genes bundled together in prokaryotic cells and eukaryotic cells?
Prokaryotic cells - single circular chromosome
Eukaryotic cell - multiple linear chromosome
What are the 3 stages of gene expression/protein synthesis?
- Transcription
- mRNA processing
- Translation
What is transcription?
the process of synthesising a strand of mRNA that is complementary to the DNA base sequence of the gene being read
(makes a copy of a specific gene)
Where does trandcription occur?
inside the nucleus before the mRNA leaves the nucleus
What is the promoter region?
- Indicates the location on chromosome where gene starts
- not transcribed
What is the template strand?
- Strand of the DNA that is transcribed
- All thymine bases will be replaced with uracil
What are the 3 stages of transcription?
- Initiation
- Elongation
- Termination
What is transcription initiation?
- Transcription factors (proteins) bind to the promoter region. This helps RNA polymerase bind to the DNA
- RNA polymerase unwinds the DNA by breaking hydrogen bonds
What is transcription elongation?
- RNA polymerase adds complementary nucleotides to the DNA
- Occurs from 5’ to 3’ direction
What is transcription termination?
- RNA polymerase is released
- 2 strands of the DNA reanneal
- Single strand of the RNA peels off the DNA
- the RNA becomes the primary RNA transcript
What is mRNA processing?
The primary RNA transcript is processed in the nucleus. It is modified in three ways before it leaves the nucleus.
What are the 3 ways the RNA is modified in?
- Caps and Tails
- Splicing the gene
- Reading the genetic code
What is caps and tails?
5’ cap - a modified guanine nucleotide is added to 5’ end.
Poly-A tail - once the whole transcript has peeled f=off the DNA, 50-250 adenine nucleotides are added to 3’ end of RNA