Chromosomal organization of genes and non-coding dna
Answers
Answer:
Explanation:
Chromosomal Organization of Genes and Noncoding DNA - Molecular Cell Biology
Genomes of Higher Eukaryotes Contain Much Nonfunctional DNA
The abundance of noncoding sequences in the genomes of higher organisms is illustrated in Figure 9-3, which depicts the protein-coding regions in an 80-kb stretch of DNA from the yeast S. cerevisiae and in the β-globin gene cluster of humans, also about 80 kb long. Note that in the single-celled yeast, protein-coding regions are closely spaced along the DNA sequence, whereas only a small fraction of the human DNA encodes protein. DNA sequencing and identification of exons has revealed that in higher organisms there is a considerable amount of DNA that does not encode protein. In fact, the β-globin gene cluster is unusually rich in protein-coding sequences compared with other regions of vertebrate DNA. In the 60-kb region including the chicken lysozyme gene, for example, the coding exons total less than 500 base pairs. Because no function has yet been found for most of the noncoding DNA in higher eukaryotes, it is commonly referred to as nonfunctional.
Figure 9-3. Diagrams of ≈80-kb region from chromosome III of the yeast S. cerevisiae and the β-globin gene cluster on human chromosome 11.