Question

Mitochondria and chloroplast perform asexual reproduction by--

Answer 1

Answer:

It is widely accepted that mitochondria and plastids evolved from bacteria that were engulfed by nucleated ancestral cells. As a relic of this evolutionary past, both types of organelles contain their own genomes, as well as their own biosynthetic machinery for making RNA and organelle proteins. Mitochondria and plastids are never made from scratch, but instead arise by the growth and division of an existing mitochondrion or plastid. On average, each organelle must double in mass in each cell generation and then be distributed into each daughter cell. Even nondividing cells must replenish organelles that are degraded as part of the continual process of organelle turnover, or produce additional organelles as the need arises. The process of organelle growth and proliferation is complicated because mitochondrial and plastid proteins are encoded in two places: the nuclear genome and the separate genomes harbored in the organelles themselves (Figure 14-50). In Chapter 12, we discuss how selected proteins and lipids are imported into mitochondria and chloroplasts from the cytosol. Here we describe how the organelle genomes are maintained and the contributions they make to organelle biogenesis.The biosynthesis of mitochondria and plastids requires contributions from two separate genetic systems. Most of the proteins in mitochondria and chloroplasts are encoded by special genes devoted to this purpose in nuclear DNA. These proteins are imported into the organelle from the cytosol after they have been synthesized on cytosolic ribosomes. Other organelle proteins are encoded by organelle DNA and synthesized on ribosomes within the organelle, using organelle-produced mRNA to specify their amino acid sequence (Figure 14-51). The protein traffic between the cytosol and these organelles seems to be unidirectional, as no known proteins are exported from mitochondria or chloroplasts to the cytosol. An exception occurs under special conditions when a cell is about to undergo apoptosis. The release of intermembrane space proteins (including cytochrome c) from mitochondria through the outer mitochondrial membrane is part of a signaling pathway that is triggered in cells undergoing programmed cell death

Explanation:

Answer 2

Mitochondria and chloroplasts divide by fission