How Do Comparative Data on Genes of Extant Species Help

question 6

Multiple Choice

How do comparative data on genes of extant species help us to make estimates of what happened before the phylogenetic event horizon?

• A) Common genes must have existed for a long time, possibly since the first life-forms.
• B) Common functional genes imply the minimal characteristics of early cells.
• C) If the first life-forms consisted of RNA, then current RNA-coding genes must be the ancestral genes.
• D) The first life-forms must have been endosymbionts because most small-genome extant bacteria are endosymbionts.

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