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Biochemistry

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Evidence for the Enosymbiotic Theory

BIOCHM-MEPBKX

The idea that chloroplasts and mitochondria were once free-living bacteria was first proposed by Mereschkowsky and Wallin, respectively, in the early 1900s.

However, the endosymbiotic theory, i.e., that mitochondria and chloroplasts evolved from bacteria following engulfment and the loss/transfer of much of their genetic material to the host nucleus, would not have become well accepted without the championing of Dr. Lynn Margulis beginning in the 1960s.

Identify ALL of the following statements which are NOT strong evidence for the endosymbiotic theory.

Select ALL that apply.

A

Genome sequencing comparisons suggest mitochondria arose from a Rickettsial bacteria, whereas chloroplasts first arose from a red alga.

B

Mitochondria and chloroplasts, like bacteria, divide by binary fission.

C

Mitochondria and chloroplasts divide independently of cell division.

D

Mitochondria and most chloroplasts are surrounded by double phospholipid bilayers, the outer of which resembles the host plasma membrane in composition.

E

Mitochondria and chloroplasts are similar in size to bacteria, about 1-10 mm in size.

F

Genome sequencing has demonstrated the presence of mitochondrial and chloroplast genes in host cytosolic circular plasmids.

G

Mitochondrial and chloroplast ribosomes are more similar to 70S bacterial ribosomes than they are to 80S ribosomes in eukaryotes.

H

Mitochondrial and chloroplast proteins, like bacterial proteins, use N-formylmethionine (fMet) as the initiating amino acid, unlike eukaryotic translation.