2D Gene Expression

Question 1

Three steps in Gene expression (In eukaryotes)

Answer 1

1. Transcription
2. RNA Processing
3. Translation

Question 2

What occurs in Transcription?

Answer 2

• DNA unwinds
• RNA Polymerase binds to Promoter region and starts synthesizing a pre-mRNA strand from free floating RNA nucleotides (i.e Using Uracil instead of Thymine)
• The base sequence of the strand is made to be complimentary to the DNA Template strand

Question 3

What occurs in RNA Processing?

Answer 3

• Methyl-G cap added to 5’ end and Poly-A tail added to 3’ end of the pre-mRNA for stability
• Introns are spliced out from the primary transcript

Question 4

What occurs in Translation?

Answer 4

• Ribosome binds to mRNA
• tRNA molecules, carrying their corresponding tRNA molecules, travel to the mRNA
• Specific tRNA molecules bind anticodons with their corresponding codons on the mRNA and deposit their amino acids to return to the cytosol
• adjacent amino acids form peptide bonds to make the polypeptide chain

Question 5

Where does each step occur?

Answer 5

Transcription: Nucleus/cytoplasm
RNA Processing: Nucleus/NA
Translation: Cytoplasm/Cytoplasm

Question 6

‘Explain the outcome of alternative splicing in relation to gene expression’

Answer 6

• Different lengths + sequences of mRNA are made
• Therefore, different proteins can be made from the one gene

Question 7

What happens in alternative splicing?

Answer 7

• Exons may be removed from pre-mRNA by a spliceosome during RNA Processing
• Allows a gene to create different mRNA strands and code for different proteins