Respuesta :
The question is incomplete. The complete question is:
Hemoglobin is an oxygen‑transport protein found in the red blood cells of all vertebrates. In mice, hemoglobin is a complex of four subunits, 2 α‑globin chains and 2nd β‑globin chains, with each subunit containing a heme molecule. The mouse β‑globin gene is approximately 1,500 nucleotides long; however, the cytoplasmic β‑globin mRNA is only about 750 nucleotides long. What's the best explanations for the difference in length.
a. The B globin gene is interrupted by one or more introns.
b. The beginning of the Bglobin gene is not transcribed
c. The globin mRNA underwent splicing in the cytoplasm.
d. The B-globin mRNA is processed after being transcribed.
e.The B-globin gene encodes both of the B-globin subunits.
Answer:
a. The B globin gene is interrupted by one or more introns.
d. The B-globin mRNA is processed after being transcribed.
Explanation:
Vertebrates are eukaryotes and eukaryotic DNA has introns and exons. The introns are the non-protein coding sequences that are present between the protein-coding exons. However, transcription of eukaryotic genes forms the primary transcripts which in turn undergo post-transcriptional modification to become mature mRNA. It includes the splicing of the introns and ligation of exons.
The mature mRNA serves as a template for protein synthesis. Therefore, the mature mRNA of eukaryotes are shorter than their respective genes. The mouse β globin gene must have one or more introns. However, the removal of introns from the primary transcript after transcription would produce a relatively shorter mRNA. The process of splicing of introns occurs in the nucleus itself.
