In: Biology
1. If all cell types have the exact same genome, how can they be different from one another?
2. do you think transcription through introns is sufficient to explain transcription of 75% of the genome? Why or why not?
1) All the cells in a person's body have the same DNA and the same genes. However, in different tissues and organs, the expression of the genes differs between cells that lead to the difference between cells in different tissues. For example, liver cells have different proteins than skin cells, even though their DNA is the same.
2) Yes, I think transcription through introns is sufficient to explain transcription of 75% of the genome. In human, percentage of DNA spanned by genes is between 25% and 38%, percentage of exons is 1.1 to 1.4%, and percentage of introns is 24% to 37%. The exons percentage is very less in the genome, and introns percentage is much more in the genome. If the transcription of 75% of the genome occurs then the transcription in introns must happen. During transcription, the entire gene is copied into a pre-mRNA that includes exons and introns. After that, in the process of RNA splicing, introns are removed and exons joined to form a contiguous coding sequence.