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.
Correct Answer:

Verified
Correct Answer:
Verified
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