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| Unit 3: Demos |
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Operon Tutorial (optional, but helpful!) Positive v. negative control of prokaryotic gene transcription Transcription of eukaryotic vs. prokaryotic genomes (6c) How Does Methylation Control Synthesis of Proteins? optional: Human
clone produces stem cells ... Or
not? Evidence found that data were fraudulent Yolk content and cleavage in human eggs (15c) Notochord
development (17a) Comparative development (18b) Determinate v. indeterminate cleavage & embryonic induction Unit 3 Slides (accompanying text can be found in your Survival Manual on pages 59-61.) |
The Relationship Between Genomic Composition and Organismal Complexity Several trends are evident when we compare the genomes of prokaryotes and those of eukaryotes, including more complex groups such as mammals. Although there are exceptions, we find a general progression from smaller to larger genomes, but with fewer genes in a given length of DNA. For example, humans have 500-1500 times as many base pairs in their genome as most prokaryotes, but on average only 5 to 15 as many genes - thus many fewer genes in any given length of DNA. In prokaryotic genmes, most of the DNA codes for protein, tRNA, or rRNA; the small amount of noncoding DNA consists mainly of regulatory sequences, such as promoters. The coding sequence of nucleotides along a prokaryotic gene proceeds from start to finish without interruption by noncoding sequences (introns). In eukaryotic genomes, by contrast, most of the DNA does not encode protein or RNA, and it includes more complex regulatory sequences. In fact, humans have 10,000 times as much noncoding DNA as prokaryotes. Some of the noncoding DNA in multicellular eukaryotes is present as introns within genes. Indeed, introns account for most of the difference in average length between human genes (27,000 base pairs) and prokaryotic genes (1,000 base pairs).
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