Question

Place the steps in their proper order on the figure to complete the summary of gene expression in a eukaryotic cell, Place your cursor on the boxes for hints. 

Answer 1

Gene expression in eukaryotic cell

The steps are in the following order:

1)DNA in nucleus acts as a template

2)pre-mRNA is processed before leaving the nucleus

3)mRNA moves into cytoplasm and become associated with ribosomes

4)tRNAs with anticodons carry amino acids to mRNA.

5) Anticodon-codon complementary base pairing occurs.

6) Polypeptide synthesis takes place one amino acid at a time.

7)At termination, the ribosome detaches from the ER, ribosomal subunits and mRNA dissociates

8)When a ribosome attaches to rough ER, the polypeptide enters it's lumen,where the polypeptides fold and modifies further.

Gene expression is eukaryotes is mainly composed of two processes. These are:

Transcription

Translation

In transcription, the gene to be expressed or converted to the protein product forms mRNA.

In eukaryotes, pre-mRNA is produced prior to the mRNA.

The pre-mRNA consists of regions called introns(non coding regions) and exons(coding regions).

The pre-mRNA processing removes the introns and the mRNA, which is ready to be translated is formed.

The process of transcription occurs in the nucleus.

The DNA is a large molecule and is bound in the nucleus, whereas the mRNA is a smaller molecule and can exit the nucleus.

Translation is the process of conversion of mRNA into proteins.

This process occurs in the cytoplasm and is aided by ribosomes.

Ribosomes are cell organelle that exist freely in the cell composed of protein and rRNA.

In eukaryotes, the ribosomes are larger with sedimentation coefficient of 80S, containing a larger and a smaller subunit.

The subunits come closer and bind to the mRNA near the 5' end.

After binding, the ribosomes read the mRNA sequence to produce amino acids.

The larger subunit of ribosome has three binding sites:

Aminoacyl tRNA binding site- A site

The peptidyl-tRNA binding site- P site

Exit site - E site.

The aminoacyl tRNAs carrying amino acids bind to the A site.

Anticodons in the tRNA and codons in mRNA undergo complementary base pairing.

In the P site, the tRNA with growing polypeptide chain binds.

Prior to release from the ribosomes, the tRNA binds to the E site.

This process repeats and the polypeptide chain is synthesized.

The termination occurs when eukaryotic release factors recognize the stop codons.

The polypeptide is in its primary structure and therefore do not function.

Protein folding is therefore necessary for the functional protein to form.

This is achieved with the help of endoplasmic reticulum.

The ribosomes attach to the endoplasmic reticulum and folded protein is released.